[ty] Demonstrate SIGSEGV via salsa

This is a demonstration of what I believe must imply unsoundness
somewhere inside of Salsa. That is, I don't use any `unsafe`, but I get
an "invalid memory reference" error.

Here is the backtrace I get from `gdb`:

```
(gdb) bt
 #0  ty_python_semantic::module_resolver::path::{impl#33}::eq (self=<error reading variable: Cannot access memory at address 0x7ff80efb0bd0>, other=0x7ffff106fcb0) at crates/ty_python_semantic/src/module_resolver/path.rs:452
 #1  0x0000555555ccc9fb in alloc::sync::{impl#50}::eq<ty_python_semantic::module_resolver::path::SearchPathInner, alloc::alloc::Global> (self=0x7ffff0110470, other=0x7ffff1033660)
     at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/sync.rs:3358
 #2  0x0000555555ccc6a4 in alloc::sync::{impl#51}::eq<ty_python_semantic::module_resolver::path::SearchPathInner, alloc::alloc::Global> (self=0x7ffff0110470, other=0x7ffff1033660)
     at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/sync.rs:3388
 #3  0x0000555555b92744 in ty_python_semantic::module_resolver::path::{impl#40}::eq (self=0x7ffff0110470, other=0x7ffff1033660) at crates/ty_python_semantic/src/module_resolver/path.rs:491
 #4  0x00005555562a4239 in core::cmp::impls::{impl#9}::eq<ty_python_semantic::module_resolver::path::SearchPath, ty_python_semantic::module_resolver::path::SearchPath> (self=0x7ffff0e88f50, other=0x7ffff7c755c8)
     at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/cmp.rs:2027
 #5  0x00005555562a4436 in core::tuple::{impl#10}::eq<(), &ty_python_semantic::module_resolver::path::SearchPath> (self=0x7ffff0e88f50, other=0x7ffff7c755c8)
     at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/tuple.rs:32
 #6  0x00005555562a44f2 in core::cmp::impls::{impl#9}::eq<((), &ty_python_semantic::module_resolver::path::SearchPath), ((), &ty_python_semantic::module_resolver::path::SearchPath)> (self=0x7ffff7c75178, other=0x7ffff7c75180)
     at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/cmp.rs:2027
 #7  salsa::interned::{impl#14}::eq<((), &ty_python_semantic::module_resolver::path::SearchPath)> (self=0x7ffff0e88f50, data=0x7ffff7c755c8) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/interned.rs:1161
 #8  0x0000555555c172e7 in salsa::interned::IngredientImpl<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_>::value_eq<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_, ((), &ty_python_semantic::module_resolver::path::SearchPath)> (id=..., key=0x7ffff7c755c8, zalsa=0x7ffff000daa0, found_value=0x7ffff7c755e8)
     at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/interned.rs:763
 #9  0x0000555555ca12b7 in salsa::interned::{impl#7}::intern_id::{closure#0}<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_, ((), &ty_python_semantic::module_resolver::path::SearchPath), ty_python_semantic::module_resolver::list::list_modules_in::{closure#0}::{closure_env#0}> (id=0x7ffff0e3a588) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/interned.rs:374
 #10 0x00005555565a907e in hashbrown::raw::{impl#8}::find::{closure#0}<salsa::id::Id, allocator_api2::stable::alloc::global::Global, salsa::interned::{impl#7}::intern_id::{closure_env#0}<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_, ((), &ty_python_semantic::module_resolver::path::SearchPath), ty_python_semantic::module_resolver::list::list_modules_in::{closure#0}::{closure_env#0}>> (index=0)
     at /home/andrew/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/hashbrown-0.15.5/src/raw/mod.rs:1197
 #11 0x00005555565821ec in hashbrown::raw::RawTableInner::find_inner (self=0x7ffff0098e08, hash=16887370829962692076, eq=...) at /home/andrew/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/hashbrown-0.15.5/src/raw/mod.rs:1921
 #12 hashbrown::raw::RawTable<salsa::id::Id, allocator_api2::stable::alloc::global::Global>::find<salsa::id::Id, allocator_api2::stable::alloc::global::Global, salsa::interned::{impl#7}::intern_id::{closure_env#0}<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_, ((), &ty_python_semantic::module_resolver::path::SearchPath), ty_python_semantic::module_resolver::list::list_modules_in::{closure#0}::{closure_env#0}>> (
     self=0x7ffff0098e08, hash=16887370829962692076, eq=...) at /home/andrew/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/hashbrown-0.15.5/src/raw/mod.rs:1197
 #13 0x0000555555c4f7f7 in hashbrown::raw::RawTable<salsa::id::Id, allocator_api2::stable::alloc::global::Global>::get<salsa::id::Id, allocator_api2::stable::alloc::global::Global, salsa::interned::{impl#7}::intern_id::{closure_env#0}<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_, ((), &ty_python_semantic::module_resolver::path::SearchPath), ty_python_semantic::module_resolver::list::list_modules_in::{closure#0}::{closure_env#0}>> (self=0x7ffff0098e08, hash=16887370829962692076, eq=...) at /home/andrew/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/hashbrown-0.15.5/src/raw/mod.rs:1212
 #14 hashbrown::table::HashTable<salsa::id::Id, allocator_api2::stable::alloc::global::Global>::find<salsa::id::Id, allocator_api2::stable::alloc::global::Global, salsa::interned::{impl#7}::intern_id::{closure_env#0}<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_, ((), &ty_python_semantic::module_resolver::path::SearchPath), ty_python_semantic::module_resolver::list::list_modules_in::{closure#0}::{closure_env#0}>> (
     self=0x7ffff0098e08, hash=16887370829962692076, eq=...) at /home/andrew/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/hashbrown-0.15.5/src/table.rs:224
 #15 salsa::interned::IngredientImpl<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_>::intern_id<ty_python_semantic::module_resolver::list::list_modules_in::list_modules_in_Configuration_, ((), &ty_python_semantic::module_resolver::path::SearchPath), ty_python_semantic::module_resolver::list::list_modules_in::{closure#0}::{closure_env#0}> (self=0x7ffff00982c0, zalsa=0x7ffff000daa0, zalsa_local=0x7ffff7c785a8,
     key=..., assemble=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/interned.rs:377
 #16 0x0000555555a24e68 in ty_python_semantic::module_resolver::list::list_modules_in::{closure#0} () at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/components/salsa-macro-rules/src/setup_tracked_fn.rs:473
 #17 0x000055555647410c in salsa::attach::Attached::attach<dyn ty_python_semantic::db::Db, alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, ty_python_semantic::module_resolver::list::list_modules_in::{closure_env#0}> (self=0x7ffff7c7a618, db=..., op=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/attach.rs:79
 #18 0x0000555556470f92 in salsa::attach::attach::{closure#0}<alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, dyn ty_python_semantic::db::Db, ty_python_semantic::module_resolver::list::list_modules_in::{closure_env#0}> (a=0x7ffff7c7a618) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/attach.rs:103
 #19 0x0000555556304feb in std::thread::local::LocalKey<salsa::attach::Attached>::try_with<salsa::attach::Attached, salsa::attach::attach::{closure_env#0}<alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, dyn ty_python_semantic::db::Db, ty_python_semantic::module_resolver::list::list_modules_in::{closure_env#0}>, alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>> (
     self=0x555557db8810, f=...) at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:315
 #20 0x00005555562e7c8d in std::thread::local::LocalKey<salsa::attach::Attached>::with<salsa::attach::Attached, salsa::attach::attach::{closure_env#0}<alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, dyn ty_python_semantic::db::Db, ty_python_semantic::module_resolver::list::list_modules_in::{closure_env#0}>, alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>> (
     self=0x555557db8810, f=<error reading variable: Cannot access memory at address 0x0>) at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:279
 #21 0x000055555646f5e4 in salsa::attach::attach<alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, dyn ty_python_semantic::db::Db, ty_python_semantic::module_resolver::list::list_modules_in::{closure_env#0}> (db=..., op=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/attach.rs:101
 #22 0x0000555555cc9f94 in ty_python_semantic::module_resolver::list::list_modules_in (db=..., search_path=0x7ffff1033660)
     at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/components/salsa-macro-rules/src/setup_tracked_fn.rs:468
 #23 0x0000555555cc95b5 in ty_python_semantic::module_resolver::list::list_modules::{impl#2}::execute::inner_ (db=...) at crates/ty_python_semantic/src/module_resolver/list.rs:20
 #24 0x0000555555cc946b in ty_python_semantic::module_resolver::list::list_modules::{impl#2}::execute (db=...)
     at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/components/salsa-macro-rules/src/setup_tracked_fn.rs:302
 #25 0x00005555561c575a in salsa::function::IngredientImpl<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>::execute_query<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_> (db=..., zalsa=0x7ffff000daa0, active_query=..., opt_old_memo=..., id=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/function/execute.rs:311
 #26 0x0000555556211b9d in salsa::function::IngredientImpl<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>::execute<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_> (self=0x7ffff0098010, db=..., active_query=..., opt_old_memo=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/function/execute.rs:46
 #27 0x0000555556143974 in salsa::function::IngredientImpl<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>::fetch_cold<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_> (self=0x7ffff0098010, zalsa=0x7ffff000daa0, zalsa_local=0x7ffff7c785a8, db=..., id=..., memo_ingredient_index=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/function/fetch.rs:235
 #28 0x00005555561775d0 in salsa::function::IngredientImpl<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>::fetch_cold_with_retry<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_> (self=0x7ffff0098010, zalsa=0x7ffff000daa0, zalsa_local=0x7ffff7c785a8, db=..., id=..., memo_ingredient_index=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/function/fetch.rs:107
 #29 0x0000555556754069 in salsa::function::fetch::{impl#0}::refresh_memo::{closure#0}<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_> ()
     at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/function/fetch.rs:64
 #30 0x00005555562d0891 in core::option::Option<&salsa::function::memo::Memo<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>>::or_else<&salsa::function::memo::Memo<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>, salsa::function::fetch::{impl#0}::refresh_memo::{closure_env#0}<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>> (self=..., f=...)
 --Type <RET> for more, q to quit, c to continue without paging--
     at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1609
 #31 0x0000555556183e04 in salsa::function::IngredientImpl<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>::refresh_memo<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_> (self=0x7ffff0098010, db=..., zalsa=0x7ffff000daa0, zalsa_local=0x7ffff7c785a8, id=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/function/fetch.rs:63
 #32 salsa::function::IngredientImpl<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_>::fetch<ty_python_semantic::module_resolver::list::list_modules::list_modules_Configuration_> (
     self=0x7ffff0098010, db=..., zalsa=0x7ffff000daa0, zalsa_local=0x7ffff7c785a8, id=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/function/fetch.rs:30
 #33 0x0000555555a24d85 in ty_python_semantic::module_resolver::list::list_modules::{closure#0} () at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/components/salsa-macro-rules/src/setup_tracked_fn.rs:474
 #34 0x0000555556474dd4 in salsa::attach::Attached::attach<dyn ty_python_semantic::db::Db, alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, ty_python_semantic::module_resolver::list::list_modules::{closure_env#0}> (self=0x7ffff7c7a618, db=..., op=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/attach.rs:79
 #35 0x0000555556470491 in salsa::attach::attach::{closure#0}<alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, dyn ty_python_semantic::db::Db, ty_python_semantic::module_resolver::list::list_modules::{closure_env#0}> (a=0x7ffff7c7a618) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/attach.rs:103
 #36 0x00005555563064e6 in std::thread::local::LocalKey<salsa::attach::Attached>::try_with<salsa::attach::Attached, salsa::attach::attach::{closure_env#0}<alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, dyn ty_python_semantic::db::Db, ty_python_semantic::module_resolver::list::list_modules::{closure_env#0}>, alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>> (
     self=0x555557db8810, f=...) at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:315
 #37 0x00005555562e897d in std::thread::local::LocalKey<salsa::attach::Attached>::with<salsa::attach::Attached, salsa::attach::attach::{closure_env#0}<alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, dyn ty_python_semantic::db::Db, ty_python_semantic::module_resolver::list::list_modules::{closure_env#0}>, alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>> (self=0x555557db8810,
     f=<error reading variable: Cannot access memory at address 0x0>) at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/local.rs:279
 #38 0x000055555646f265 in salsa::attach::attach<alloc::vec::Vec<ty_python_semantic::module_resolver::module::Module, alloc::alloc::Global>, dyn ty_python_semantic::db::Db, ty_python_semantic::module_resolver::list::list_modules::{closure_env#0}> (db=..., op=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/src/attach.rs:101
 #39 0x0000555555cc93c7 in ty_python_semantic::module_resolver::list::list_modules (db=...) at /home/andrew/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/a3ffa22/components/salsa-macro-rules/src/setup_tracked_fn.rs:468
 #40 0x00005555557e2186 in ty_test::run_module_resolution_consistency_test (db=0x7ffff7c78598) at crates/ty_test/src/lib.rs:450
 #41 0x00005555557defec in ty_test::run (absolute_fixture_path=..., relative_fixture_path=..., snapshot_path=..., short_title=..., test_name=..., output_format=ty_test::OutputFormat::Cli) at crates/ty_test/src/lib.rs:73
 #42 0x0000555555793c06 in mdtest::mdtest (fixture=...) at crates/ty_python_semantic/tests/mdtest.rs:29
 #43 0x00005555557959c1 in mdtest::mdtest__generics_pep695_classes () at crates/ty_python_semantic/tests/mdtest.rs:7
 #44 0x00005555557903a7 in mdtest::mdtest__generics_pep695_classes::{closure#0} () at crates/ty_python_semantic/tests/mdtest.rs:10
 #45 0x000055555579a1b6 in core::ops::function::FnOnce::call_once<mdtest::mdtest__generics_pep695_classes::{closure_env#0}, ()> ()
     at /home/andrew/.rustup/toolchains/1.89-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250
 #46 0x00005555557d98eb in core::ops::function::FnOnce::call_once<fn() -> core::result::Result<(), alloc::string::String>, ()> () at library/core/src/ops/function.rs:250
 #47 test::__rust_begin_short_backtrace<core::result::Result<(), alloc::string::String>, fn() -> core::result::Result<(), alloc::string::String>> () at library/test/src/lib.rs:648
 #48 0x00005555557d8b6e in test::run_test_in_process::{closure#0} () at library/test/src/lib.rs:671
 #49 core::panic::unwind_safe::{impl#23}::call_once<core::result::Result<(), alloc::string::String>, test::run_test_in_process::{closure_env#0}> () at library/core/src/panic/unwind_safe.rs:272
 #50 std::panicking::catch_unwind::do_call<core::panic::unwind_safe::AssertUnwindSafe<test::run_test_in_process::{closure_env#0}>, core::result::Result<(), alloc::string::String>> () at library/std/src/panicking.rs:589
 #51 std::panicking::catch_unwind<core::result::Result<(), alloc::string::String>, core::panic::unwind_safe::AssertUnwindSafe<test::run_test_in_process::{closure_env#0}>> () at library/std/src/panicking.rs:552
 #52 std::panic::catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<test::run_test_in_process::{closure_env#0}>, core::result::Result<(), alloc::string::String>> () at library/std/src/panic.rs:359
 #53 test::run_test_in_process () at library/test/src/lib.rs:671
 #54 test::run_test::{closure#0} () at library/test/src/lib.rs:592
 #55 0x000055555579d944 in test::run_test::{closure#1} () at library/test/src/lib.rs:622
 #56 std::sys::backtrace::__rust_begin_short_backtrace<test::run_test::{closure_env#1}, ()> () at library/std/src/sys/backtrace.rs:152
 #57 0x00005555557a10ca in std::thread::{impl#0}::spawn_unchecked_::{closure#1}::{closure#0}<test::run_test::{closure_env#1}, ()> () at library/std/src/thread/mod.rs:559
 #58 core::panic::unwind_safe::{impl#23}::call_once<(), std::thread::{impl#0}::spawn_unchecked_::{closure#1}::{closure_env#0}<test::run_test::{closure_env#1}, ()>> () at library/core/src/panic/unwind_safe.rs:272
 #59 std::panicking::catch_unwind::do_call<core::panic::unwind_safe::AssertUnwindSafe<std::thread::{impl#0}::spawn_unchecked_::{closure#1}::{closure_env#0}<test::run_test::{closure_env#1}, ()>>, ()> ()
     at library/std/src/panicking.rs:589
 #60 std::panicking::catch_unwind<(), core::panic::unwind_safe::AssertUnwindSafe<std::thread::{impl#0}::spawn_unchecked_::{closure#1}::{closure_env#0}<test::run_test::{closure_env#1}, ()>>> () at library/std/src/panicking.rs:552
 #61 std::panic::catch_unwind<core::panic::unwind_safe::AssertUnwindSafe<std::thread::{impl#0}::spawn_unchecked_::{closure#1}::{closure_env#0}<test::run_test::{closure_env#1}, ()>>, ()> () at library/std/src/panic.rs:359
 #62 std::thread::{impl#0}::spawn_unchecked_::{closure#1}<test::run_test::{closure_env#1}, ()> () at library/std/src/thread/mod.rs:557
 #63 core::ops::function::FnOnce::call_once<std::thread::{impl#0}::spawn_unchecked_::{closure_env#1}<test::run_test::{closure_env#1}, ()>, ()> () at library/core/src/ops/function.rs:250
 #64 0x000055555705088f in alloc::boxed::{impl#28}::call_once<(), dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global> () at library/alloc/src/boxed.rs:1966
 #65 std::sys::pal::unix::thread::{impl#2}::new::thread_start () at library/std/src/sys/pal/unix/thread.rs:107
 #66 0x00007ffff7d127eb in ?? () from /usr/lib/libc.so.6
 #67 0x00007ffff7d9618c in ?? () from /usr/lib/libc.so.6
```

.github/workflows/build-binaries.yml

@@ -49,7 +49,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build sdist"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           command: sdist
           args: --out dist
@@ -79,7 +79,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels - x86_64"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           target: x86_64
           args: --release --locked --out dist
@@ -121,7 +121,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels - aarch64"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           target: aarch64
           args: --release --locked --out dist
@@ -177,7 +177,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           target: ${{ matrix.platform.target }}
           args: --release --locked --out dist
@@ -230,7 +230,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           target: ${{ matrix.target }}
           manylinux: auto
@@ -306,7 +306,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           target: ${{ matrix.platform.target }}
           manylinux: auto
@@ -372,7 +372,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           target: ${{ matrix.target }}
           manylinux: musllinux_1_2
@@ -437,7 +437,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           target: ${{ matrix.platform.target }}
           manylinux: musllinux_1_2

.github/workflows/ci.yaml

@@ -715,7 +715,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@e10f6c464b90acceb5f640d31beda6d586ba7b4a # v1.49.3
+        uses: PyO3/maturin-action@86b9d133d34bc1b40018696f782949dac11bd380 # v1.49.4
         with:
           args: --out dist
       - name: "Test wheel"

.github/workflows/mypy_primer.yaml

@@ -11,6 +11,7 @@ on:
       - "crates/ruff_python_parser"
       - ".github/workflows/mypy_primer.yaml"
       - ".github/workflows/mypy_primer_comment.yaml"
+      - "scripts/mypy_primer.sh"
       - "Cargo.lock"
       - "!**.md"
 

.github/workflows/release.yml

@@ -61,7 +61,7 @@ jobs:
     env:
       GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@09d2acae674a48949e3602304ab46fd20ae0c42f
+      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
         with:
           persist-credentials: false
           submodules: recursive
@@ -124,7 +124,7 @@ jobs:
       GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       BUILD_MANIFEST_NAME: target/distrib/global-dist-manifest.json
     steps:
-      - uses: actions/checkout@09d2acae674a48949e3602304ab46fd20ae0c42f
+      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
         with:
           persist-credentials: false
           submodules: recursive
@@ -175,7 +175,7 @@ jobs:
     outputs:
       val: ${{ steps.host.outputs.manifest }}
     steps:
-      - uses: actions/checkout@09d2acae674a48949e3602304ab46fd20ae0c42f
+      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
         with:
           persist-credentials: false
           submodules: recursive
@@ -251,7 +251,7 @@ jobs:
     env:
       GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
     steps:
-      - uses: actions/checkout@09d2acae674a48949e3602304ab46fd20ae0c42f
+      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
         with:
           persist-credentials: false
           submodules: recursive

.github/workflows/typing_conformance.yaml

@@ -54,6 +54,9 @@ jobs:
 
       - name: Compute diagnostic diff
         shell: bash
+        env:
+          # TODO: Remove this once we fixed the remaining panics in the conformance suite.
+          TY_MAX_PARALLELISM: 1
         run: |
           RUFF_DIR="$GITHUB_WORKSPACE/ruff"
 
@@ -63,15 +66,15 @@ jobs:
 
             echo "new commit"
             git rev-list --format=%s --max-count=1 "$GITHUB_SHA"
-            cargo build --release --bin ty
-            mv target/release/ty ty-new
+            cargo build --bin ty
+            mv target/debug/ty ty-new
 
             MERGE_BASE="$(git merge-base "$GITHUB_SHA" "origin/$GITHUB_BASE_REF")"
             git checkout -b old_commit "$MERGE_BASE"
             echo "old commit (merge base)"
             git rev-list --format=%s --max-count=1 old_commit
-            cargo build --release --bin ty
-            mv target/release/ty ty-old
+            cargo build --bin ty
+            mv target/debug/ty ty-old
           )
 
           (

CHANGELOG.md

@@ -24,8 +24,31 @@
 ### Other changes
 
 - Build `riscv64` binaries for release ([#19819](https://github.com/astral-sh/ruff/pull/19819))
+
 - Add rule code to error description in GitLab output ([#19896](https://github.com/astral-sh/ruff/pull/19896))
 
+- Improve rendering of the `full` output format ([#19415](https://github.com/astral-sh/ruff/pull/19415))
+
+    Below is an example diff for [`F401`](https://docs.astral.sh/ruff/rules/unused-import/):
+
+    ```diff
+    -unused.py:8:19: F401 [*] `pathlib` imported but unused
+    +F401 [*] `pathlib` imported but unused
+    +  --> unused.py:8:19
+        |
+      7 | # Unused, _not_ marked as required (due to the alias).
+      8 | import pathlib as non_alias
+    -   |                   ^^^^^^^^^ F401
+    +   |                   ^^^^^^^^^
+      9 |
+     10 | # Unused, marked as required.
+        |
+    -   = help: Remove unused import: `pathlib`
+    +help: Remove unused import: `pathlib`
+    ```
+
+    For now, the primary difference is the movement of the filename, line number, and column information to a second line in the header. This new representation will allow us to make further additions to Ruff's diagnostics, such as adding sub-diagnostics and multiple annotations to the same snippet.
+
 ## 0.12.8
 
 ### Preview features

Cargo.lock

@@ -128,9 +128,9 @@ dependencies = [
 
 [[package]]
 name = "anyhow"
-version = "1.0.98"
+version = "1.0.99"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e16d2d3311acee920a9eb8d33b8cbc1787ce4a264e85f964c2404b969bdcd487"
+checksum = "b0674a1ddeecb70197781e945de4b3b8ffb61fa939a5597bcf48503737663100"
 
 [[package]]
 name = "approx"
@@ -257,9 +257,9 @@ checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
 [[package]]
 name = "bitflags"
-version = "2.9.1"
+version = "2.9.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1b8e56985ec62d17e9c1001dc89c88ecd7dc08e47eba5ec7c29c7b5eeecde967"
+checksum = "6a65b545ab31d687cff52899d4890855fec459eb6afe0da6417b8a18da87aa29"
 
 [[package]]
 name = "bitvec"
@@ -408,9 +408,9 @@ dependencies = [
 
 [[package]]
 name = "clap"
-version = "4.5.43"
+version = "4.5.45"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "50fd97c9dc2399518aa331917ac6f274280ec5eb34e555dd291899745c48ec6f"
+checksum = "1fc0e74a703892159f5ae7d3aac52c8e6c392f5ae5f359c70b5881d60aaac318"
 dependencies = [
  "clap_builder",
  "clap_derive",
@@ -418,9 +418,9 @@ dependencies = [
 
 [[package]]
 name = "clap_builder"
-version = "4.5.43"
+version = "4.5.44"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c35b5830294e1fa0462034af85cc95225a4cb07092c088c55bda3147cfcd8f65"
+checksum = "b3e7f4214277f3c7aa526a59dd3fbe306a370daee1f8b7b8c987069cd8e888a8"
 dependencies = [
  "anstream",
  "anstyle",
@@ -461,9 +461,9 @@ dependencies = [
 
 [[package]]
 name = "clap_derive"
-version = "4.5.41"
+version = "4.5.45"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef4f52386a59ca4c860f7393bcf8abd8dfd91ecccc0f774635ff68e92eeef491"
+checksum = "14cb31bb0a7d536caef2639baa7fad459e15c3144efefa6dbd1c84562c4739f6"
 dependencies = [
  "heck",
  "proc-macro2",
@@ -1218,9 +1218,9 @@ dependencies = [
 
 [[package]]
 name = "glob"
-version = "0.3.2"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a8d1add55171497b4705a648c6b583acafb01d58050a51727785f0b2c8e0a2b2"
+checksum = "0cc23270f6e1808e30a928bdc84dea0b9b4136a8bc82338574f23baf47bbd280"
 
 [[package]]
 name = "globset"
@@ -1241,7 +1241,7 @@ version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0bf760ebf69878d9fd8f110c89703d90ce35095324d1f1edcb595c63945ee757"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "ignore",
  "walkdir",
 ]
@@ -1521,7 +1521,7 @@ version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f37dccff2791ab604f9babef0ba14fbe0be30bd368dc541e2b08d07c8aa908f3"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "inotify-sys",
  "libc",
 ]
@@ -1764,9 +1764,9 @@ checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 
 [[package]]
 name = "libc"
-version = "0.2.174"
+version = "0.2.175"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1171693293099992e19cddea4e8b849964e9846f4acee11b3948bcc337be8776"
+checksum = "6a82ae493e598baaea5209805c49bbf2ea7de956d50d7da0da1164f9c6d28543"
 
 [[package]]
 name = "libcst"
@@ -1809,7 +1809,7 @@ version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "391290121bad3d37fbddad76d8f5d1c1c314cfc646d143d7e07a3086ddff0ce3"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "libc",
  "redox_syscall",
 ]
@@ -2014,7 +2014,7 @@ version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "71e2746dc3a24dd78b3cfcb7be93368c6de9963d30f43a6a73998a9cf4b17b46"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "cfg-if",
  "cfg_aliases",
  "libc",
@@ -2026,7 +2026,7 @@ version = "0.30.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "74523f3a35e05aba87a1d978330aef40f67b0304ac79c1c00b294c9830543db6"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "cfg-if",
  "cfg_aliases",
  "libc",
@@ -2054,7 +2054,7 @@ version = "8.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4d3d07927151ff8575b7087f245456e549fea62edf0ec4e565a5ee50c8402bc3"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "fsevent-sys",
  "inotify",
  "kqueue",
@@ -2666,7 +2666,7 @@ version = "0.5.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5407465600fb0548f1442edf71dd20683c6ed326200ace4b1ef0763521bb3b77"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
 ]
 
 [[package]]
@@ -2749,7 +2749,7 @@ dependencies = [
  "argfile",
  "assert_fs",
  "bincode 2.0.1",
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "cachedir",
  "clap",
  "clap_complete_command",
@@ -3000,7 +3000,7 @@ version = "0.12.9"
 dependencies = [
  "aho-corasick",
  "anyhow",
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "clap",
  "colored 3.0.0",
  "fern",
@@ -3106,7 +3106,7 @@ name = "ruff_python_ast"
 version = "0.0.0"
 dependencies = [
  "aho-corasick",
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "compact_str",
  "get-size2",
  "is-macro",
@@ -3194,7 +3194,7 @@ dependencies = [
 name = "ruff_python_literal"
 version = "0.0.0"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "itertools 0.14.0",
  "ruff_python_ast",
  "unic-ucd-category",
@@ -3205,7 +3205,7 @@ name = "ruff_python_parser"
 version = "0.0.0"
 dependencies = [
  "anyhow",
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "bstr",
  "compact_str",
  "get-size2",
@@ -3230,7 +3230,7 @@ dependencies = [
 name = "ruff_python_semantic"
 version = "0.0.0"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "insta",
  "is-macro",
  "ruff_cache",
@@ -3251,7 +3251,7 @@ dependencies = [
 name = "ruff_python_stdlib"
 version = "0.0.0"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "unicode-ident",
 ]
 
@@ -3428,7 +3428,7 @@ version = "1.0.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "11181fbabf243db407ef8df94a6ce0b2f9a733bd8be4ad02b4eda9602296cac8"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "errno",
  "libc",
  "linux-raw-sys",
@@ -3450,7 +3450,7 @@ checksum = "28d3b2b1366ec20994f1fd18c3c594f05c5dd4bc44d8bb0c1c632c8d6829481f"
 [[package]]
 name = "salsa"
 version = "0.23.0"
-source = "git+https://github.com/salsa-rs/salsa.git?rev=918d35d873b2b73a0237536144ef4d22e8d57f27#918d35d873b2b73a0237536144ef4d22e8d57f27"
+source = "git+https://github.com/salsa-rs/salsa.git?rev=a3ffa22cb26756473d56f867aedec3fd907c4dd9#a3ffa22cb26756473d56f867aedec3fd907c4dd9"
 dependencies = [
  "boxcar",
  "compact_str",
@@ -3474,12 +3474,12 @@ dependencies = [
 [[package]]
 name = "salsa-macro-rules"
 version = "0.23.0"
-source = "git+https://github.com/salsa-rs/salsa.git?rev=918d35d873b2b73a0237536144ef4d22e8d57f27#918d35d873b2b73a0237536144ef4d22e8d57f27"
+source = "git+https://github.com/salsa-rs/salsa.git?rev=a3ffa22cb26756473d56f867aedec3fd907c4dd9#a3ffa22cb26756473d56f867aedec3fd907c4dd9"
 
 [[package]]
 name = "salsa-macros"
 version = "0.23.0"
-source = "git+https://github.com/salsa-rs/salsa.git?rev=918d35d873b2b73a0237536144ef4d22e8d57f27#918d35d873b2b73a0237536144ef4d22e8d57f27"
+source = "git+https://github.com/salsa-rs/salsa.git?rev=a3ffa22cb26756473d56f867aedec3fd907c4dd9#a3ffa22cb26756473d56f867aedec3fd907c4dd9"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -4238,7 +4238,7 @@ dependencies = [
 name = "ty_ide"
 version = "0.0.0"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "insta",
  "itertools 0.14.0",
  "regex",
@@ -4297,7 +4297,7 @@ name = "ty_python_semantic"
 version = "0.0.0"
 dependencies = [
  "anyhow",
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "bitvec",
  "camino",
  "colored 3.0.0",
@@ -4350,7 +4350,7 @@ name = "ty_server"
 version = "0.0.0"
 dependencies = [
  "anyhow",
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "crossbeam",
  "dunce",
  "insta",
@@ -4393,7 +4393,7 @@ name = "ty_test"
 version = "0.0.0"
 dependencies = [
  "anyhow",
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
  "camino",
  "colored 3.0.0",
  "insta",
@@ -5143,7 +5143,7 @@ version = "0.39.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6f42320e61fe2cfd34354ecb597f86f413484a798ba44a8ca1165c58d42da6c1"
 dependencies = [
- "bitflags 2.9.1",
+ "bitflags 2.9.2",
 ]
 
 [[package]]

Cargo.toml

@@ -5,7 +5,7 @@ resolver = "2"
 [workspace.package]
 # Please update rustfmt.toml when bumping the Rust edition
 edition = "2024"
-rust-version = "1.86"
+rust-version = "1.87"
 homepage = "https://docs.astral.sh/ruff"
 documentation = "https://docs.astral.sh/ruff"
 repository = "https://github.com/astral-sh/ruff"
@@ -143,7 +143,7 @@ regex-automata = { version = "0.4.9" }
 rustc-hash = { version = "2.0.0" }
 rustc-stable-hash = { version = "0.1.2" }
 # When updating salsa, make sure to also update the revision in `fuzz/Cargo.toml`
-salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "918d35d873b2b73a0237536144ef4d22e8d57f27", default-features = false, features = [
+salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "a3ffa22cb26756473d56f867aedec3fd907c4dd9", default-features = false, features = [
     "compact_str",
     "macros",
     "salsa_unstable",

crates/ruff/tests/lint.rs

@@ -5588,15 +5588,15 @@ fn cookiecutter_globbing() -> Result<()> {
                 .args(STDIN_BASE_OPTIONS)
                 .arg("--select=F811")
                 .current_dir(tempdir.path()), @r"
-			success: false
-			exit_code: 1
-			----- stdout -----
-			{{cookiecutter.repo_name}}/tests/maintest.py:3:8: F811 [*] Redefinition of unused `foo` from line 1
-			Found 1 error.
-			[*] 1 fixable with the `--fix` option.
+        success: false
+        exit_code: 1
+        ----- stdout -----
+        {{cookiecutter.repo_name}}/tests/maintest.py:3:8: F811 [*] Redefinition of unused `foo` from line 1: `foo` redefined here
+        Found 1 error.
+        [*] 1 fixable with the `--fix` option.
 
-			----- stderr -----
-		");
+        ----- stderr -----
+        ");
     });
 
     Ok(())
@@ -5801,3 +5801,32 @@ fn future_annotations_preview_warning() {
     ",
     );
 }
+
+#[test]
+fn up045_nested_optional_flatten_all() {
+    let contents = "\
+from typing import Optional
+nested_optional: Optional[Optional[Optional[str]]] = None
+";
+
+    assert_cmd_snapshot!(
+        Command::new(get_cargo_bin(BIN_NAME))
+            .args(STDIN_BASE_OPTIONS)
+            .args(["--select", "UP045", "--diff", "--target-version", "py312"])
+            .arg("-")
+            .pass_stdin(contents),
+        @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    @@ -1,2 +1,2 @@
+     from typing import Optional
+    -nested_optional: Optional[Optional[Optional[str]]] = None
+    +nested_optional: str | None = None
+
+
+    ----- stderr -----
+    Would fix 1 error.
+    ",
+    );
+}

crates/ruff_db/src/diagnostic/mod.rs

@@ -254,6 +254,11 @@ impl Diagnostic {
             .find(|ann| ann.is_primary)
     }
 
+    /// Returns a mutable borrow of all annotations of this diagnostic.
+    pub fn annotations_mut(&mut self) -> impl Iterator<Item = &mut Annotation> {
+        Arc::make_mut(&mut self.inner).annotations.iter_mut()
+    }
+
     /// Returns the "primary" span of this diagnostic if one exists.
     ///
     /// When there are multiple primary spans, then the first one that was
@@ -310,6 +315,11 @@ impl Diagnostic {
         &self.inner.subs
     }
 
+    /// Returns a mutable borrow of the sub-diagnostics of this diagnostic.
+    pub fn sub_diagnostics_mut(&mut self) -> impl Iterator<Item = &mut SubDiagnostic> {
+        Arc::make_mut(&mut self.inner).subs.iter_mut()
+    }
+
     /// Returns the fix for this diagnostic if it exists.
     pub fn fix(&self) -> Option<&Fix> {
         self.inner.fix.as_ref()
@@ -621,6 +631,11 @@ impl SubDiagnostic {
         &self.inner.annotations
     }
 
+    /// Returns a mutable borrow of the annotations of this sub-diagnostic.
+    pub fn annotations_mut(&mut self) -> impl Iterator<Item = &mut Annotation> {
+        self.inner.annotations.iter_mut()
+    }
+
     /// Returns a shared borrow of the "primary" annotation of this diagnostic
     /// if one exists.
     ///

crates/ruff_db/src/diagnostic/render.rs

@@ -264,7 +264,12 @@ impl<'a> ResolvedDiagnostic<'a> {
             .annotations
             .iter()
             .filter_map(|ann| {
-                let path = ann.span.file.path(resolver);
+                let path = ann
+                    .span
+                    .file
+                    .relative_path(resolver)
+                    .to_str()
+                    .unwrap_or_else(|| ann.span.file.path(resolver));
                 let diagnostic_source = ann.span.file.diagnostic_source(resolver);
                 ResolvedAnnotation::new(path, &diagnostic_source, ann, resolver)
             })

crates/ruff_db/src/files.rs

@@ -87,11 +87,12 @@ impl Files {
             .system_by_path
             .entry(absolute.clone())
             .or_insert_with(|| {
-                tracing::trace!("Adding file '{path}'");
-
                 let metadata = db.system().path_metadata(path);
+
+                tracing::trace!("Adding file '{absolute}'");
+
                 let durability = self
-                    .root(db, path)
+                    .root(db, &absolute)
                     .map_or(Durability::default(), |root| root.durability(db));
 
                 let builder = File::builder(FilePath::System(absolute))

crates/ruff_linter/resources/test/fixtures/flake8_simplify/SIM905.py

@@ -166,3 +166,7 @@ r"""first
 print("S\x1cP\x1dL\x1eI\x1fT".split())
 print("\x1c\x1d\x1e\x1f>".split(maxsplit=0))
 print("<\x1c\x1d\x1e\x1f".rsplit(maxsplit=0))
+
+# leading/trailing whitespace should not count towards maxsplit
+" a b c d ".split(maxsplit=2)  # ["a", "b", "c d "]
+" a b c d ".rsplit(maxsplit=2)  # [" a b", "c", "d"]

crates/ruff_linter/resources/test/fixtures/isort/required_imports/docstring_with_multiple_continuations.py

@@ -0,0 +1,4 @@
+"""Hello, world!"""\
+\
+
+x = 1; y = 2

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP045.py

@@ -69,3 +69,10 @@ a7: OptionalTE[typing.NamedTuple] = None
 a8: typing_extensions.Optional[typing.NamedTuple] = None
 a9: "Optional[NamedTuple]" = None
 a10: Optional[NamedTupleTE] = None
+
+
+# Test for: https://github.com/astral-sh/ruff/issues/19746
+# Nested Optional types should be flattened
+nested_optional: Optional[Optional[str]] = None
+nested_optional_typing: typing.Optional[Optional[int]] = None
+triple_nested_optional: Optional[Optional[Optional[str]]] = None

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -28,7 +28,7 @@ use itertools::Itertools;
 use log::debug;
 use rustc_hash::{FxHashMap, FxHashSet};
 
-use ruff_db::diagnostic::Diagnostic;
+use ruff_db::diagnostic::{Annotation, Diagnostic, IntoDiagnosticMessage, Span};
 use ruff_diagnostics::{Applicability, Fix, IsolationLevel};
 use ruff_notebook::{CellOffsets, NotebookIndex};
 use ruff_python_ast::helpers::{collect_import_from_member, is_docstring_stmt, to_module_path};
@@ -3305,6 +3305,17 @@ impl DiagnosticGuard<'_, '_> {
             Err(err) => log::debug!("Failed to create fix for {}: {}", self.name(), err),
         }
     }
+
+    /// Add a secondary annotation with the given message and range.
+    pub(crate) fn secondary_annotation<'a>(
+        &mut self,
+        message: impl IntoDiagnosticMessage + 'a,
+        range: impl Ranged,
+    ) {
+        let span = Span::from(self.context.source_file.clone()).with_range(range.range());
+        let ann = Annotation::secondary(span).message(message);
+        self.diagnostic.as_mut().unwrap().annotate(ann);
+    }
 }
 
 impl std::ops::Deref for DiagnosticGuard<'_, '_> {

crates/ruff_linter/src/importer/insertion.rs

@@ -63,9 +63,9 @@ impl<'a> Insertion<'a> {
                 return Insertion::inline(" ", location.add(offset).add(TextSize::of(';')), ";");
             }
 
-            // If the first token after the docstring is a continuation character (i.e. "\"), advance
-            // an additional row to prevent inserting in the same logical line.
-            if match_continuation(locator.after(location)).is_some() {
+            // While the first token after the docstring is a continuation character (i.e. "\"), advance
+            // additional rows to prevent inserting in the same logical line.
+            while match_continuation(locator.after(location)).is_some() {
                 location = locator.full_line_end(location);
             }
 
@@ -379,6 +379,17 @@ mod tests {
             Insertion::own_line("", TextSize::from(22), "\n")
         );
 
+        let contents = r#"
+"""Hello, world!"""\
+\
+
+"#
+        .trim_start();
+        assert_eq!(
+            insert(contents)?,
+            Insertion::own_line("", TextSize::from(24), "\n")
+        );
+
         let contents = r"
 x = 1
 "

crates/ruff_linter/src/preview.rs

@@ -230,3 +230,8 @@ pub(crate) const fn is_add_future_annotations_imports_enabled(settings: &LinterS
 pub(crate) const fn is_trailing_comma_type_params_enabled(settings: &LinterSettings) -> bool {
     settings.preview.is_enabled()
 }
+
+// https://github.com/astral-sh/ruff/pull/19851
+pub(crate) const fn is_maxsplit_without_separator_fix_enabled(settings: &LinterSettings) -> bool {
+    settings.preview.is_enabled()
+}

crates/ruff_linter/src/rules/flake8_annotations/rules/definition.rs

@@ -485,9 +485,6 @@ impl Violation for MissingReturnTypeClassMethod {
 /// Use instead:
 ///
 /// ```python
-/// from typing import Any
-///
-///
 /// def foo(x: int): ...
 /// ```
 ///

crates/ruff_linter/src/rules/flake8_pyi/rules/future_annotations_in_stub.rs

@@ -16,7 +16,7 @@ use crate::{checkers::ast::Checker, fix};
 /// statement has no effect and should be omitted.
 ///
 /// ## References
-/// - [Static Typing with Python: Type Stubs](https://typing.python.org/en/latest/source/stubs.html)
+/// - [Typing Style Guide](https://typing.python.org/en/latest/guides/writing_stubs.html#language-features)
 #[derive(ViolationMetadata)]
 pub(crate) struct FutureAnnotationsInStub;
 

crates/ruff_linter/src/rules/flake8_simplify/mod.rs

@@ -60,6 +60,7 @@ mod tests {
     }
 
     #[test_case(Rule::MultipleWithStatements, Path::new("SIM117.py"))]
+    #[test_case(Rule::SplitStaticString, Path::new("SIM905.py"))]
     fn preview_rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!(
             "preview__{}_{}",

crates/ruff_linter/src/rules/flake8_simplify/rules/split_static_string.rs

@@ -9,6 +9,8 @@ use ruff_python_ast::{
 use ruff_text_size::{Ranged, TextRange};
 
 use crate::checkers::ast::Checker;
+use crate::preview::is_maxsplit_without_separator_fix_enabled;
+use crate::settings::LinterSettings;
 use crate::{Applicability, Edit, Fix, FixAvailability, Violation};
 
 /// ## What it does
@@ -84,7 +86,9 @@ pub(crate) fn split_static_string(
     let sep_arg = arguments.find_argument_value("sep", 0);
     let split_replacement = if let Some(sep) = sep_arg {
         match sep {
-            Expr::NoneLiteral(_) => split_default(str_value, maxsplit_value, direction),
+            Expr::NoneLiteral(_) => {
+                split_default(str_value, maxsplit_value, direction, checker.settings())
+            }
             Expr::StringLiteral(sep_value) => {
                 let sep_value_str = sep_value.value.to_str();
                 Some(split_sep(
@@ -100,7 +104,7 @@ pub(crate) fn split_static_string(
             }
         }
     } else {
-        split_default(str_value, maxsplit_value, direction)
+        split_default(str_value, maxsplit_value, direction, checker.settings())
     };
 
     let mut diagnostic = checker.report_diagnostic(SplitStaticString, call.range());
@@ -174,6 +178,7 @@ fn split_default(
     str_value: &StringLiteralValue,
     max_split: i32,
     direction: Direction,
+    settings: &LinterSettings,
 ) -> Option<Expr> {
     // From the Python documentation:
     // > If sep is not specified or is None, a different splitting algorithm is applied: runs of
@@ -185,10 +190,31 @@ fn split_default(
     let string_val = str_value.to_str();
     match max_split.cmp(&0) {
         Ordering::Greater => {
-            // Autofix for `maxsplit` without separator not yet implemented, as
-            // `split_whitespace().remainder()` is not stable:
-            // https://doc.rust-lang.org/std/str/struct.SplitWhitespace.html#method.remainder
-            None
+            if !is_maxsplit_without_separator_fix_enabled(settings) {
+                return None;
+            }
+            let Ok(max_split) = usize::try_from(max_split) else {
+                return None;
+            };
+            let list_items: Vec<&str> = if direction == Direction::Left {
+                string_val
+                    .trim_start_matches(py_unicode_is_whitespace)
+                    .splitn(max_split + 1, py_unicode_is_whitespace)
+                    .filter(|s| !s.is_empty())
+                    .collect()
+            } else {
+                let mut items: Vec<&str> = string_val
+                    .trim_end_matches(py_unicode_is_whitespace)
+                    .rsplitn(max_split + 1, py_unicode_is_whitespace)
+                    .filter(|s| !s.is_empty())
+                    .collect();
+                items.reverse();
+                items
+            };
+            Some(construct_replacement(
+                &list_items,
+                str_value.first_literal_flags(),
+            ))
         }
         Ordering::Equal => {
             // Behavior for maxsplit = 0 when sep is None:

crates/ruff_linter/src/rules/flake8_simplify/snapshots/ruff_linter__rules__flake8_simplify__tests__SIM905_SIM905.py.snap

@@ -1439,6 +1439,7 @@ help: Replace with list literal
     166 |+print(["S", "P", "L", "I", "T"])
 167 167 | print("\x1c\x1d\x1e\x1f>".split(maxsplit=0))
 168 168 | print("<\x1c\x1d\x1e\x1f".rsplit(maxsplit=0))
+169 169 | 
 
 SIM905 [*] Consider using a list literal instead of `str.split`
    --> SIM905.py:167:7
@@ -1458,6 +1459,8 @@ help: Replace with list literal
 167     |-print("\x1c\x1d\x1e\x1f>".split(maxsplit=0))
     167 |+print([">"])
 168 168 | print("<\x1c\x1d\x1e\x1f".rsplit(maxsplit=0))
+169 169 | 
+170 170 | # leading/trailing whitespace should not count towards maxsplit
 
 SIM905 [*] Consider using a list literal instead of `str.split`
    --> SIM905.py:168:7
@@ -1466,6 +1469,8 @@ SIM905 [*] Consider using a list literal instead of `str.split`
 167 | print("\x1c\x1d\x1e\x1f>".split(maxsplit=0))
 168 | print("<\x1c\x1d\x1e\x1f".rsplit(maxsplit=0))
     |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+169 |
+170 | # leading/trailing whitespace should not count towards maxsplit
     |
 help: Replace with list literal
 
@@ -1475,3 +1480,26 @@ help: Replace with list literal
 167 167 | print("\x1c\x1d\x1e\x1f>".split(maxsplit=0))
 168     |-print("<\x1c\x1d\x1e\x1f".rsplit(maxsplit=0))
     168 |+print(["<"])
+169 169 | 
+170 170 | # leading/trailing whitespace should not count towards maxsplit
+171 171 | " a b c d ".split(maxsplit=2)  # ["a", "b", "c d "]
+
+SIM905 Consider using a list literal instead of `str.split`
+   --> SIM905.py:171:1
+    |
+170 | # leading/trailing whitespace should not count towards maxsplit
+171 | " a b c d ".split(maxsplit=2)  # ["a", "b", "c d "]
+    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+172 | " a b c d ".rsplit(maxsplit=2)  # [" a b", "c", "d"]
+    |
+help: Replace with list literal
+
+SIM905 Consider using a list literal instead of `str.split`
+   --> SIM905.py:172:1
+    |
+170 | # leading/trailing whitespace should not count towards maxsplit
+171 | " a b c d ".split(maxsplit=2)  # ["a", "b", "c d "]
+172 | " a b c d ".rsplit(maxsplit=2)  # [" a b", "c", "d"]
+    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    |
+help: Replace with list literal

crates/ruff_linter/src/rules/isort/mod.rs

@@ -797,6 +797,7 @@ mod tests {
     #[test_case(Path::new("docstring_followed_by_continuation.py"))]
     #[test_case(Path::new("docstring_only.py"))]
     #[test_case(Path::new("docstring_with_continuation.py"))]
+    #[test_case(Path::new("docstring_with_multiple_continuations.py"))]
     #[test_case(Path::new("docstring_with_semicolon.py"))]
     #[test_case(Path::new("empty.py"))]
     #[test_case(Path::new("existing_import.py"))]
@@ -832,6 +833,7 @@ mod tests {
     #[test_case(Path::new("docstring_followed_by_continuation.py"))]
     #[test_case(Path::new("docstring_only.py"))]
     #[test_case(Path::new("docstring_with_continuation.py"))]
+    #[test_case(Path::new("docstring_with_multiple_continuations.py"))]
     #[test_case(Path::new("docstring_with_semicolon.py"))]
     #[test_case(Path::new("empty.py"))]
     #[test_case(Path::new("existing_import.py"))]

crates/ruff_linter/src/rules/isort/snapshots/ruff_linter__rules__isort__tests__required_import_docstring_with_multiple_continuations.py.snap

@@ -0,0 +1,13 @@
+---
+source: crates/ruff_linter/src/rules/isort/mod.rs
+---
+I002 [*] Missing required import: `from __future__ import annotations`
+--> docstring_with_multiple_continuations.py:1:1
+help: Insert required import: `from __future__ import annotations`
+
+ℹ Safe fix
+1 1 | """Hello, world!"""\
+2 2 | \
+3 3 | 
+  4 |+from __future__ import annotations
+4 5 | x = 1; y = 2

crates/ruff_linter/src/rules/isort/snapshots/ruff_linter__rules__isort__tests__required_import_with_alias_docstring_with_multiple_continuations.py.snap

@@ -0,0 +1,13 @@
+---
+source: crates/ruff_linter/src/rules/isort/mod.rs
+---
+I002 [*] Missing required import: `from __future__ import annotations as _annotations`
+--> docstring_with_multiple_continuations.py:1:1
+help: Insert required import: `from __future__ import annotations as _annotations`
+
+ℹ Safe fix
+1 1 | """Hello, world!"""\
+2 2 | \
+3 3 | 
+  4 |+from __future__ import annotations as _annotations
+4 5 | x = 1; y = 2

crates/ruff_linter/src/rules/pycodestyle/rules/blank_lines.rs

@@ -60,7 +60,7 @@ const BLANK_LINES_NESTED_LEVEL: u32 = 1;
 /// ## References
 /// - [PEP 8: Blank Lines](https://peps.python.org/pep-0008/#blank-lines)
 /// - [Flake 8 rule](https://www.flake8rules.com/rules/E301.html)
-/// - [Typing Style Guide](https://typing.python.org/en/latest/source/stubs.html#blank-lines)
+/// - [Typing Style Guide](https://typing.python.org/en/latest/guides/writing_stubs.html#blank-lines)
 #[derive(ViolationMetadata)]
 pub(crate) struct BlankLineBetweenMethods;
 
@@ -113,7 +113,7 @@ impl AlwaysFixableViolation for BlankLineBetweenMethods {
 /// ## References
 /// - [PEP 8: Blank Lines](https://peps.python.org/pep-0008/#blank-lines)
 /// - [Flake 8 rule](https://www.flake8rules.com/rules/E302.html)
-/// - [Typing Style Guide](https://typing.python.org/en/latest/source/stubs.html#blank-lines)
+/// - [Typing Style Guide](https://typing.python.org/en/latest/guides/writing_stubs.html#blank-lines)
 #[derive(ViolationMetadata)]
 pub(crate) struct BlankLinesTopLevel {
     actual_blank_lines: u32,
@@ -180,7 +180,7 @@ impl AlwaysFixableViolation for BlankLinesTopLevel {
 /// ## References
 /// - [PEP 8: Blank Lines](https://peps.python.org/pep-0008/#blank-lines)
 /// - [Flake 8 rule](https://www.flake8rules.com/rules/E303.html)
-/// - [Typing Style Guide](https://typing.python.org/en/latest/source/stubs.html#blank-lines)
+/// - [Typing Style Guide](https://typing.python.org/en/latest/guides/writing_stubs.html#blank-lines)
 #[derive(ViolationMetadata)]
 pub(crate) struct TooManyBlankLines {
     actual_blank_lines: u32,
@@ -277,7 +277,7 @@ impl AlwaysFixableViolation for BlankLineAfterDecorator {
 /// ## References
 /// - [PEP 8: Blank Lines](https://peps.python.org/pep-0008/#blank-lines)
 /// - [Flake 8 rule](https://www.flake8rules.com/rules/E305.html)
-/// - [Typing Style Guide](https://typing.python.org/en/latest/source/stubs.html#blank-lines)
+/// - [Typing Style Guide](https://typing.python.org/en/latest/guides/writing_stubs.html#blank-lines)
 #[derive(ViolationMetadata)]
 pub(crate) struct BlankLinesAfterFunctionOrClass {
     actual_blank_lines: u32,
@@ -331,7 +331,7 @@ impl AlwaysFixableViolation for BlankLinesAfterFunctionOrClass {
 /// ## References
 /// - [PEP 8: Blank Lines](https://peps.python.org/pep-0008/#blank-lines)
 /// - [Flake 8 rule](https://www.flake8rules.com/rules/E306.html)
-/// - [Typing Style Guide](https://typing.python.org/en/latest/source/stubs.html#blank-lines)
+/// - [Typing Style Guide](https://typing.python.org/en/latest/guides/writing_stubs.html#blank-lines)
 #[derive(ViolationMetadata)]
 pub(crate) struct BlankLinesBeforeNestedDefinition;
 

crates/ruff_linter/src/rules/pycodestyle/rules/lambda_assignment.rs

@@ -10,7 +10,7 @@ use ruff_source_file::UniversalNewlines;
 use ruff_text_size::{Ranged, TextRange};
 
 use crate::checkers::ast::Checker;
-use crate::{Edit, Fix, FixAvailability, Violation};
+use crate::{Applicability, Edit, Fix, FixAvailability, Violation};
 
 /// ## What it does
 /// Checks for lambda expressions which are assigned to a variable.
@@ -105,29 +105,24 @@ pub(crate) fn lambda_assignment(
             }
         }
 
-        // Otherwise, if the assignment is in a class body, flag it, but use a display-only fix.
-        // Rewriting safely would require making this a static method.
-        //
-        // Similarly, if the lambda is shadowing a variable in the current scope,
+        // If the lambda is shadowing a variable in the current scope,
         // rewriting it as a function declaration may break type-checking.
         // See: https://github.com/astral-sh/ruff/issues/5421
-        if checker.semantic().current_scope().kind.is_class()
-            || checker
-                .semantic()
-                .current_scope()
-                .get_all(id)
-                .any(|binding_id| checker.semantic().binding(binding_id).kind.is_annotation())
+        let applicability = if checker
+            .semantic()
+            .current_scope()
+            .get_all(id)
+            .any(|binding_id| checker.semantic().binding(binding_id).kind.is_annotation())
         {
-            diagnostic.set_fix(Fix::display_only_edit(Edit::range_replacement(
-                indented,
-                stmt.range(),
-            )));
+            Applicability::DisplayOnly
         } else {
-            diagnostic.set_fix(Fix::unsafe_edit(Edit::range_replacement(
-                indented,
-                stmt.range(),
-            )));
-        }
+            Applicability::Unsafe
+        };
+
+        diagnostic.set_fix(Fix::applicable_edit(
+            Edit::range_replacement(indented, stmt.range()),
+            applicability,
+        ));
     }
 }
 

crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E731_E731.py.snap

@@ -105,7 +105,7 @@ help: Rewrite `f` as a `def`
 26 27 | 
 27 28 | def scope():
 
-E731 Do not assign a `lambda` expression, use a `def`
+E731 [*] Do not assign a `lambda` expression, use a `def`
   --> E731.py:57:5
    |
 55 | class Scope:
@@ -115,7 +115,7 @@ E731 Do not assign a `lambda` expression, use a `def`
    |
 help: Rewrite `f` as a `def`
 
-ℹ Display-only fix
+ℹ Unsafe fix
 54 54 | 
 55 55 | class Scope:
 56 56 |     # E731
@@ -318,7 +318,7 @@ help: Rewrite `f` as a `def`
 137 138 | 
 138 139 | class TemperatureScales(Enum):
 
-E731 Do not assign a `lambda` expression, use a `def`
+E731 [*] Do not assign a `lambda` expression, use a `def`
    --> E731.py:139:5
     |
 138 | class TemperatureScales(Enum):
@@ -328,7 +328,7 @@ E731 Do not assign a `lambda` expression, use a `def`
     |
 help: Rewrite `CELSIUS` as a `def`
 
-ℹ Display-only fix
+ℹ Unsafe fix
 136 136 | 
 137 137 | 
 138 138 | class TemperatureScales(Enum):
@@ -339,7 +339,7 @@ help: Rewrite `CELSIUS` as a `def`
 141 142 | 
 142 143 | 
 
-E731 Do not assign a `lambda` expression, use a `def`
+E731 [*] Do not assign a `lambda` expression, use a `def`
    --> E731.py:140:5
     |
 138 | class TemperatureScales(Enum):
@@ -349,7 +349,7 @@ E731 Do not assign a `lambda` expression, use a `def`
     |
 help: Rewrite `FAHRENHEIT` as a `def`
 
-ℹ Display-only fix
+ℹ Unsafe fix
 137 137 | 
 138 138 | class TemperatureScales(Enum):
 139 139 |     CELSIUS = (lambda deg_c: deg_c)

crates/ruff_linter/src/rules/pyflakes/rules/redefined_while_unused.rs

@@ -183,14 +183,24 @@ pub(crate) fn redefined_while_unused(checker: &Checker, scope_id: ScopeId, scope
     // Create diagnostics for each statement.
     for (source, entries) in &redefinitions {
         for (shadowed, binding) in entries {
+            let name = binding.name(checker.source());
             let mut diagnostic = checker.report_diagnostic(
                 RedefinedWhileUnused {
-                    name: binding.name(checker.source()).to_string(),
+                    name: name.to_string(),
                     row: checker.compute_source_row(shadowed.start()),
                 },
                 binding.range(),
             );
 
+            diagnostic.secondary_annotation(
+                format_args!("previous definition of `{name}` here"),
+                shadowed,
+            );
+
+            if let Some(ann) = diagnostic.primary_annotation_mut() {
+                ann.set_message(format_args!("`{name}` redefined here"));
+            }
+
             if let Some(range) = binding.parent_range(checker.semantic()) {
                 diagnostic.set_parent(range.start());
             }

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_0.py.snap

@@ -5,7 +5,14 @@ F811 Redefinition of unused `bar` from line 6
   --> F811_0.py:10:5
    |
 10 | def bar():
-   |     ^^^
+   |     ^^^ `bar` redefined here
 11 |     pass
    |
+  ::: F811_0.py:6:5
+   |
+ 5 | @foo
+ 6 | def bar():
+   |     --- previous definition of `bar` here
+ 7 |     pass
+   |
 help: Remove definition: `bar`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_1.py.snap

@@ -2,9 +2,11 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `FU` from line 1
- --> F811_1.py:1:25
+ --> F811_1.py:1:14
   |
 1 | import fu as FU, bar as FU
-  |                         ^^
+  |              --         ^^ `FU` redefined here
+  |              |
+  |              previous definition of `FU` here
   |
 help: Remove definition: `FU`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_12.py.snap

@@ -2,12 +2,16 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `mixer` from line 2
- --> F811_12.py:6:20
+ --> F811_12.py:2:20
   |
+1 | try:
+2 |     from aa import mixer
+  |                    ----- previous definition of `mixer` here
+3 | except ImportError:
 4 |     pass
 5 | else:
 6 |     from bb import mixer
-  |                    ^^^^^
+  |                    ^^^^^ `mixer` redefined here
 7 | mixer(123)
   |
 help: Remove definition: `mixer`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_15.py.snap

@@ -5,7 +5,12 @@ F811 Redefinition of unused `fu` from line 1
  --> F811_15.py:4:5
   |
 4 | def fu():
-  |     ^^
+  |     ^^ `fu` redefined here
 5 |     pass
   |
+ ::: F811_15.py:1:8
+  |
+1 | import fu
+  |        -- previous definition of `fu` here
+  |
 help: Remove definition: `fu`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_16.py.snap

@@ -7,7 +7,14 @@ F811 Redefinition of unused `fu` from line 3
 6 | def bar():
 7 |     def baz():
 8 |         def fu():
-  |             ^^
+  |             ^^ `fu` redefined here
 9 |             pass
   |
+ ::: F811_16.py:3:8
+  |
+1 | """Test that shadowing a global with a nested function generates a warning."""
+2 |
+3 | import fu
+  |        -- previous definition of `fu` here
+  |
 help: Remove definition: `fu`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_17.py.snap

@@ -6,10 +6,16 @@ F811 [*] Redefinition of unused `fu` from line 2
   |
 5 | def bar():
 6 |     import fu
-  |            ^^
+  |            ^^ `fu` redefined here
 7 |
 8 |     def baz():
   |
+ ::: F811_17.py:2:8
+  |
+1 | """Test that shadowing a global name with a nested function generates a warning."""
+2 | import fu
+  |        -- previous definition of `fu` here
+  |
 help: Remove definition: `fu`
 
 ℹ Safe fix
@@ -22,11 +28,15 @@ help: Remove definition: `fu`
 9 8 |         def fu():
 
 F811 Redefinition of unused `fu` from line 6
-  --> F811_17.py:9:13
+  --> F811_17.py:6:12
    |
+ 5 | def bar():
+ 6 |     import fu
+   |            -- previous definition of `fu` here
+ 7 |
  8 |     def baz():
  9 |         def fu():
-   |             ^^
+   |             ^^ `fu` redefined here
 10 |             pass
    |
 help: Remove definition: `fu`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_2.py.snap

@@ -2,9 +2,11 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `FU` from line 1
- --> F811_2.py:1:34
+ --> F811_2.py:1:23
   |
 1 | from moo import fu as FU, bar as FU
-  |                                  ^^
+  |                       --         ^^ `FU` redefined here
+  |                       |
+  |                       previous definition of `FU` here
   |
 help: Remove definition: `FU`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_21.py.snap

@@ -7,9 +7,17 @@ F811 [*] Redefinition of unused `Sequence` from line 26
 30 | from typing import (
 31 |     List,  # noqa: F811
 32 |     Sequence,
-   |     ^^^^^^^^
+   |     ^^^^^^^^ `Sequence` redefined here
 33 | )
    |
+  ::: F811_21.py:26:5
+   |
+24 | from typing import (
+25 |     List,  # noqa
+26 |     Sequence,  # noqa
+   |     -------- previous definition of `Sequence` here
+27 | )
+   |
 help: Remove definition: `Sequence`
 
 ℹ Safe fix

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_23.py.snap

@@ -2,10 +2,13 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `foo` from line 3
- --> F811_23.py:4:15
+ --> F811_23.py:3:15
   |
+1 | """Test that shadowing an explicit re-export produces a warning."""
+2 |
 3 | import foo as foo
+  |               --- previous definition of `foo` here
 4 | import bar as foo
-  |               ^^^
+  |               ^^^ `foo` redefined here
   |
 help: Remove definition: `foo`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_26.py.snap

@@ -2,12 +2,15 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `func` from line 2
- --> F811_26.py:5:9
+ --> F811_26.py:2:9
   |
+1 | class Class:
+2 |     def func(self):
+  |         ---- previous definition of `func` here
 3 |         pass
 4 |
 5 |     def func(self):
-  |         ^^^^
+  |         ^^^^ `func` redefined here
 6 |         pass
   |
 help: Remove definition: `func`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_28.py.snap

@@ -2,11 +2,14 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `datetime` from line 3
- --> F811_28.py:4:22
+ --> F811_28.py:3:8
   |
+1 | """Regression test for: https://github.com/astral-sh/ruff/issues/10384"""
+2 |
 3 | import datetime
+  |        -------- previous definition of `datetime` here
 4 | from datetime import datetime
-  |                      ^^^^^^^^
+  |                      ^^^^^^^^ `datetime` redefined here
 5 |
 6 | datetime(1, 2, 3)
   |

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_29.pyi.snap

@@ -2,11 +2,17 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `Bar` from line 3
- --> F811_29.pyi:8:1
+ --> F811_29.pyi:3:24
   |
+1 | """Regression test for: https://github.com/astral-sh/ruff/issues/10509"""
+2 |
+3 | from foo import Bar as Bar
+  |                        --- previous definition of `Bar` here
+4 |
+5 | class Eggs:
 6 |     Bar: int  # OK
 7 |
 8 | Bar = 1  # F811
-  | ^^^
+  | ^^^ `Bar` redefined here
   |
 help: Remove definition: `Bar`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_3.py.snap

@@ -2,9 +2,11 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `fu` from line 1
- --> F811_3.py:1:12
+ --> F811_3.py:1:8
   |
 1 | import fu; fu = 3
-  |            ^^
+  |        --  ^^ `fu` redefined here
+  |        |
+  |        previous definition of `fu` here
   |
 help: Remove definition: `fu`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_30.py.snap

@@ -2,32 +2,43 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `bar` from line 10
-  --> F811_30.py:12:9
+  --> F811_30.py:10:5
    |
+ 8 |         """Foo."""
+ 9 |
 10 |     bar = foo
+   |     --- previous definition of `bar` here
 11 |
 12 |     def bar(self) -> None:
-   |         ^^^
+   |         ^^^ `bar` redefined here
 13 |         """Bar."""
    |
 help: Remove definition: `bar`
 
 F811 Redefinition of unused `baz` from line 18
-  --> F811_30.py:21:5
+  --> F811_30.py:18:9
    |
+16 | class B:
+17 |     """B."""
+18 |     def baz(self) -> None:
+   |         --- previous definition of `baz` here
 19 |         """Baz."""
 20 |
 21 |     baz = 1
-   |     ^^^
+   |     ^^^ `baz` redefined here
    |
 help: Remove definition: `baz`
 
 F811 Redefinition of unused `foo` from line 26
-  --> F811_30.py:29:12
+  --> F811_30.py:26:9
    |
+24 | class C:
+25 |     """C."""
+26 |     def foo(self) -> None:
+   |         --- previous definition of `foo` here
 27 |         """Foo."""
 28 |
 29 |     bar = (foo := 1)
-   |            ^^^
+   |            ^^^ `foo` redefined here
    |
 help: Remove definition: `foo`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_31.py.snap

@@ -2,12 +2,14 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `baz` from line 17
-  --> F811_31.py:19:29
+  --> F811_31.py:17:5
    |
+16 | try:
 17 |     baz = None
+   |     --- previous definition of `baz` here
 18 |
 19 |     from some_module import baz
-   |                             ^^^
+   |                             ^^^ `baz` redefined here
 20 | except ImportError:
 21 |     pass
    |

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_32.py.snap

@@ -2,12 +2,13 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 [*] Redefinition of unused `List` from line 4
- --> F811_32.py:5:5
+ --> F811_32.py:4:5
   |
 3 | from typing import (
 4 |     List,
+  |     ---- previous definition of `List` here
 5 |     List,
-  |     ^^^^
+  |     ^^^^ `List` redefined here
 6 | )
   |
 help: Remove definition: `List`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_4.py.snap

@@ -2,9 +2,11 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `fu` from line 1
- --> F811_4.py:1:12
+ --> F811_4.py:1:8
   |
 1 | import fu; fu, bar = 3
-  |            ^^
+  |        --  ^^ `fu` redefined here
+  |        |
+  |        previous definition of `fu` here
   |
 help: Remove definition: `fu`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_5.py.snap

@@ -2,9 +2,11 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 Redefinition of unused `fu` from line 1
- --> F811_5.py:1:13
+ --> F811_5.py:1:8
   |
 1 | import fu; [fu, bar] = 3
-  |             ^^
+  |        --   ^^ `fu` redefined here
+  |        |
+  |        previous definition of `fu` here
   |
 help: Remove definition: `fu`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_6.py.snap

@@ -2,12 +2,14 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 [*] Redefinition of unused `os` from line 5
- --> F811_6.py:6:12
+ --> F811_6.py:5:12
   |
+3 | i = 2
 4 | if i == 1:
 5 |     import os
+  |            -- previous definition of `os` here
 6 |     import os
-  |            ^^
+  |            ^^ `os` redefined here
 7 | os.path
   |
 help: Remove definition: `os`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F811_F811_8.py.snap

@@ -2,12 +2,13 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 [*] Redefinition of unused `os` from line 4
- --> F811_8.py:5:12
+ --> F811_8.py:4:12
   |
 3 | try:
 4 |     import os
+  |            -- previous definition of `os` here
 5 |     import os
-  |            ^^
+  |            ^^ `os` redefined here
 6 | except:
 7 |     pass
   |

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__del_shadowed_global_import_in_local_scope.snap

@@ -19,11 +19,14 @@ help: Remove unused import: `os`
 5 4 |     import os
 
 F811 [*] Redefinition of unused `os` from line 2
- --> <filename>:5:12
+ --> <filename>:2:8
   |
+2 | import os
+  |        -- previous definition of `os` here
+3 |
 4 | def f():
 5 |     import os
-  |            ^^
+  |            ^^ `os` redefined here
 6 |
 7 |     # Despite this `del`, `import os` in `f` should still be flagged as shadowing an unused
   |

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__del_shadowed_import_shadow_in_local_scope.snap

@@ -19,11 +19,14 @@ help: Remove unused import: `os`
 5 4 |     os = 1
 
 F811 Redefinition of unused `os` from line 2
- --> <filename>:5:5
+ --> <filename>:2:8
   |
+2 | import os
+  |        -- previous definition of `os` here
+3 |
 4 | def f():
 5 |     os = 1
-  |     ^^
+  |     ^^ `os` redefined here
 6 |     print(os)
   |
 help: Remove definition: `os`

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__del_shadowed_local_import_in_local_scope.snap

@@ -2,12 +2,13 @@
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
 ---
 F811 [*] Redefinition of unused `os` from line 3
- --> <filename>:4:12
+ --> <filename>:3:12
   |
 2 | def f():
 3 |     import os
+  |            -- previous definition of `os` here
 4 |     import os
-  |            ^^
+  |            ^^ `os` redefined here
 5 |
 6 |     # Despite this `del`, `import os` should still be flagged as shadowing an unused
   |

crates/ruff_linter/src/rules/pyupgrade/rules/use_pep604_annotation.rs

@@ -2,7 +2,7 @@ use ruff_macros::{ViolationMetadata, derive_message_formats};
 use ruff_python_ast::PythonVersion;
 use ruff_python_ast::helpers::{pep_604_optional, pep_604_union};
 use ruff_python_ast::{self as ast, Expr};
-use ruff_python_semantic::analyze::typing::Pep604Operator;
+use ruff_python_semantic::analyze::typing::{Pep604Operator, to_pep604_operator};
 use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
@@ -171,10 +171,22 @@ pub(crate) fn non_pep604_annotation(
                         // Invalid type annotation.
                     }
                     _ => {
+                        // Unwrap all nested Optional[...] and wrap once as `X | None`.
+                        let mut inner = slice;
+                        while let Expr::Subscript(ast::ExprSubscript { value, slice, .. }) = inner {
+                            if let Some(Pep604Operator::Optional) =
+                                to_pep604_operator(value, slice, checker.semantic())
+                            {
+                                inner = slice;
+                            } else {
+                                break;
+                            }
+                        }
+
                         diagnostic.set_fix(Fix::applicable_edit(
                             Edit::range_replacement(
                                 pad(
-                                    checker.generator().expr(&pep_604_optional(slice)),
+                                    checker.generator().expr(&pep_604_optional(inner)),
                                     expr.range(),
                                     checker.locator(),
                                 ),

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__UP045.py.snap

@@ -171,3 +171,134 @@ UP045 Use `X | None` for type annotations
    |      ^^^^^^^^^^^^^^
    |
 help: Convert to `X | None`
+
+UP045 [*] Use `X | None` for type annotations
+  --> UP045.py:76:18
+   |
+74 | # Test for: https://github.com/astral-sh/ruff/issues/19746
+75 | # Nested Optional types should be flattened
+76 | nested_optional: Optional[Optional[str]] = None
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^
+77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   |
+help: Convert to `X | None`
+
+ℹ Safe fix
+73 73 | 
+74 74 | # Test for: https://github.com/astral-sh/ruff/issues/19746
+75 75 | # Nested Optional types should be flattened
+76    |-nested_optional: Optional[Optional[str]] = None
+   76 |+nested_optional: str | None = None
+77 77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78 78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+
+UP045 [*] Use `X | None` for type annotations
+  --> UP045.py:76:27
+   |
+74 | # Test for: https://github.com/astral-sh/ruff/issues/19746
+75 | # Nested Optional types should be flattened
+76 | nested_optional: Optional[Optional[str]] = None
+   |                           ^^^^^^^^^^^^^
+77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   |
+help: Convert to `X | None`
+
+ℹ Safe fix
+73 73 | 
+74 74 | # Test for: https://github.com/astral-sh/ruff/issues/19746
+75 75 | # Nested Optional types should be flattened
+76    |-nested_optional: Optional[Optional[str]] = None
+   76 |+nested_optional: Optional[str | None] = None
+77 77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78 78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+
+UP045 [*] Use `X | None` for type annotations
+  --> UP045.py:77:25
+   |
+75 | # Nested Optional types should be flattened
+76 | nested_optional: Optional[Optional[str]] = None
+77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   |
+help: Convert to `X | None`
+
+ℹ Safe fix
+74 74 | # Test for: https://github.com/astral-sh/ruff/issues/19746
+75 75 | # Nested Optional types should be flattened
+76 76 | nested_optional: Optional[Optional[str]] = None
+77    |-nested_optional_typing: typing.Optional[Optional[int]] = None
+   77 |+nested_optional_typing: int | None = None
+78 78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+
+UP045 [*] Use `X | None` for type annotations
+  --> UP045.py:77:41
+   |
+75 | # Nested Optional types should be flattened
+76 | nested_optional: Optional[Optional[str]] = None
+77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+   |                                         ^^^^^^^^^^^^^
+78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   |
+help: Convert to `X | None`
+
+ℹ Safe fix
+74 74 | # Test for: https://github.com/astral-sh/ruff/issues/19746
+75 75 | # Nested Optional types should be flattened
+76 76 | nested_optional: Optional[Optional[str]] = None
+77    |-nested_optional_typing: typing.Optional[Optional[int]] = None
+   77 |+nested_optional_typing: typing.Optional[int | None] = None
+78 78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+
+UP045 [*] Use `X | None` for type annotations
+  --> UP045.py:78:25
+   |
+76 | nested_optional: Optional[Optional[str]] = None
+77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: Convert to `X | None`
+
+ℹ Safe fix
+75 75 | # Nested Optional types should be flattened
+76 76 | nested_optional: Optional[Optional[str]] = None
+77 77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78    |-triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   78 |+triple_nested_optional: str | None = None
+
+UP045 [*] Use `X | None` for type annotations
+  --> UP045.py:78:34
+   |
+76 | nested_optional: Optional[Optional[str]] = None
+77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   |                                  ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: Convert to `X | None`
+
+ℹ Safe fix
+75 75 | # Nested Optional types should be flattened
+76 76 | nested_optional: Optional[Optional[str]] = None
+77 77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78    |-triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   78 |+triple_nested_optional: Optional[str | None] = None
+
+UP045 [*] Use `X | None` for type annotations
+  --> UP045.py:78:43
+   |
+76 | nested_optional: Optional[Optional[str]] = None
+77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78 | triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   |                                           ^^^^^^^^^^^^^
+   |
+help: Convert to `X | None`
+
+ℹ Safe fix
+75 75 | # Nested Optional types should be flattened
+76 76 | nested_optional: Optional[Optional[str]] = None
+77 77 | nested_optional_typing: typing.Optional[Optional[int]] = None
+78    |-triple_nested_optional: Optional[Optional[Optional[str]]] = None
+   78 |+triple_nested_optional: Optional[Optional[str | None]] = None

crates/ruff_linter/src/test.rs

@@ -9,7 +9,7 @@ use anyhow::Result;
 use itertools::Itertools;
 use rustc_hash::FxHashMap;
 
-use ruff_db::diagnostic::Diagnostic;
+use ruff_db::diagnostic::{Diagnostic, Span};
 use ruff_notebook::Notebook;
 #[cfg(not(fuzzing))]
 use ruff_notebook::NotebookError;
@@ -281,10 +281,16 @@ Either ensure you always emit a fix or change `Violation::FIX_AVAILABILITY` to e
             // noqa offset and the source file
             let range = diagnostic.expect_range();
             diagnostic.set_noqa_offset(directives.noqa_line_for.resolve(range.start()));
-            if let Some(annotation) = diagnostic.primary_annotation_mut() {
-                annotation.set_span(
-                    ruff_db::diagnostic::Span::from(source_code.clone()).with_range(range),
-                );
+            // This part actually is necessary to avoid long relative paths in snapshots.
+            for annotation in diagnostic.annotations_mut() {
+                let range = annotation.get_span().range().unwrap();
+                annotation.set_span(Span::from(source_code.clone()).with_range(range));
+            }
+            for sub in diagnostic.sub_diagnostics_mut() {
+                for annotation in sub.annotations_mut() {
+                    let range = annotation.get_span().range().unwrap();
+                    annotation.set_span(Span::from(source_code.clone()).with_range(range));
+                }
             }
 
             diagnostic

crates/ty/docs/configuration.md

@@ -44,7 +44,7 @@ or pyright's `stubPath` configuration setting.
 
 ```toml
 [tool.ty.environment]
-extra-paths = ["~/shared/my-search-path"]
+extra-paths = ["./shared/my-search-path"]
 ```
 
 ---

crates/ty/docs/rules.md

@@ -36,7 +36,7 @@ def test(): -> "int":
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20call-non-callable) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L101)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L109)
 </small>
 
 **What it does**
@@ -58,7 +58,7 @@ Calling a non-callable object will raise a `TypeError` at runtime.
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20conflicting-argument-forms) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L145)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L153)
 </small>
 
 **What it does**
@@ -88,7 +88,7 @@ f(int)  # error
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20conflicting-declarations) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L171)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L179)
 </small>
 
 **What it does**
@@ -117,7 +117,7 @@ a = 1
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20conflicting-metaclass) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L196)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L204)
 </small>
 
 **What it does**
@@ -147,7 +147,7 @@ class C(A, B): ...
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20cyclic-class-definition) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L222)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L230)
 </small>
 
 **What it does**
@@ -177,7 +177,7 @@ class B(A): ...
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20duplicate-base) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L287)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L295)
 </small>
 
 **What it does**
@@ -202,7 +202,7 @@ class B(A, A): ...
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20duplicate-kw-only) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L308)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L316)
 </small>
 
 **What it does**
@@ -306,7 +306,7 @@ def test(): -> "Literal[5]":
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20inconsistent-mro) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L450)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L519)
 </small>
 
 **What it does**
@@ -334,7 +334,7 @@ class C(A, B): ...
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20index-out-of-bounds) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L474)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L543)
 </small>
 
 **What it does**
@@ -358,7 +358,7 @@ t[3]  # IndexError: tuple index out of range
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20instance-layout-conflict) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L340)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L348)
 </small>
 
 **What it does**
@@ -445,7 +445,7 @@ an atypical memory layout.
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-argument-type) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L519)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L588)
 </small>
 
 **What it does**
@@ -470,7 +470,7 @@ func("foo")  # error: [invalid-argument-type]
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-assignment) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L559)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L628)
 </small>
 
 **What it does**
@@ -496,7 +496,7 @@ a: int = ''
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-attribute-access) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1563)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1662)
 </small>
 
 **What it does**
@@ -523,12 +523,46 @@ C().instance_var = 3  # okay
 C.instance_var = 3  # error: Cannot assign to instance variable
 ```
 
+## `invalid-await`
+
+<small>
+Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
+[Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-await) ·
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L650)
+</small>
+
+**What it does**
+
+Checks for `await` being used with types that are not [Awaitable].
+
+**Why is this bad?**
+
+Such expressions will lead to `TypeError` being raised at runtime.
+
+**Examples**
+
+```python
+import asyncio
+
+class InvalidAwait:
+    def __await__(self) -> int:
+        return 5
+
+async def main() -> None:
+    await InvalidAwait()  # error: [invalid-await]
+    await 42  # error: [invalid-await]
+
+asyncio.run(main())
+```
+
+[Awaitable]: https://docs.python.org/3/library/collections.abc.html#collections.abc.Awaitable
+
 ## `invalid-base`
 
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-base) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L581)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L680)
 </small>
 
 **What it does**
@@ -550,7 +584,7 @@ class A(42): ...  # error: [invalid-base]
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-context-manager) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L632)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L731)
 </small>
 
 **What it does**
@@ -575,7 +609,7 @@ with 1:
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-declaration) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L653)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L752)
 </small>
 
 **What it does**
@@ -602,7 +636,7 @@ a: str
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-exception-caught) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L676)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L775)
 </small>
 
 **What it does**
@@ -644,7 +678,7 @@ except ZeroDivisionError:
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-generic-class) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L712)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L811)
 </small>
 
 **What it does**
@@ -675,7 +709,7 @@ class C[U](Generic[T]): ...
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-key) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L494)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L563)
 </small>
 
 **What it does**
@@ -704,7 +738,7 @@ alice["height"]  # KeyError: 'height'
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-legacy-type-variable) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L738)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L837)
 </small>
 
 **What it does**
@@ -737,7 +771,7 @@ def f(t: TypeVar("U")): ...
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-metaclass) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L787)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L886)
 </small>
 
 **What it does**
@@ -764,12 +798,42 @@ class B(metaclass=f): ...
 
 - [Python documentation: Metaclasses](https://docs.python.org/3/reference/datamodel.html#metaclasses)
 
+## `invalid-named-tuple`
+
+<small>
+Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
+[Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-named-tuple) ·
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L493)
+</small>
+
+**What it does**
+
+Checks for invalidly defined `NamedTuple` classes.
+
+**Why is this bad?**
+
+An invalidly defined `NamedTuple` class may lead to the type checker
+drawing incorrect conclusions. It may also lead to `TypeError`s at runtime.
+
+**Examples**
+
+A class definition cannot combine `NamedTuple` with other base classes
+in multiple inheritance; doing so raises a `TypeError` at runtime. The sole
+exception to this rule is `Generic[]`, which can be used alongside `NamedTuple`
+in a class's bases list.
+
+```pycon
+>>> from typing import NamedTuple
+>>> class Foo(NamedTuple, object): ...
+TypeError: can only inherit from a NamedTuple type and Generic
+```
+
 ## `invalid-overload`
 
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-overload) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L814)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L913)
 </small>
 
 **What it does**
@@ -817,7 +881,7 @@ def foo(x: int) -> int: ...
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-parameter-default) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L857)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L956)
 </small>
 
 **What it does**
@@ -841,12 +905,12 @@ def f(a: int = ''): ...
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-protocol) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L422)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L430)
 </small>
 
 **What it does**
 
-Checks for invalidly defined protocol classes.
+Checks for protocol classes that will raise `TypeError` at runtime.
 
 **Why is this bad?**
 
@@ -873,7 +937,7 @@ TypeError: Protocols can only inherit from other protocols, got <class 'int'>
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-raise) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L877)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L976)
 </small>
 
 Checks for `raise` statements that raise non-exceptions or use invalid
@@ -920,7 +984,7 @@ def g():
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-return-type) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L540)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L609)
 </small>
 
 **What it does**
@@ -943,7 +1007,7 @@ def func() -> int:
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-super-argument) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L920)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1019)
 </small>
 
 **What it does**
@@ -997,7 +1061,7 @@ TODO #14889
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-alias-type) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L766)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L865)
 </small>
 
 **What it does**
@@ -1022,7 +1086,7 @@ NewAlias = TypeAliasType(get_name(), int)        # error: TypeAliasType name mus
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-checking-constant) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L959)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1058)
 </small>
 
 **What it does**
@@ -1050,7 +1114,7 @@ TYPE_CHECKING = ''
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-form) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L983)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1082)
 </small>
 
 **What it does**
@@ -1078,7 +1142,7 @@ b: Annotated[int]  # `Annotated` expects at least two arguments
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-guard-call) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1035)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1134)
 </small>
 
 **What it does**
@@ -1110,7 +1174,7 @@ f(10)  # Error
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-guard-definition) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1007)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1106)
 </small>
 
 **What it does**
@@ -1142,7 +1206,7 @@ class C:
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20invalid-type-variable-constraints) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1063)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1162)
 </small>
 
 **What it does**
@@ -1175,7 +1239,7 @@ T = TypeVar('T', bound=str)  # valid bound TypeVar
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20missing-argument) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1092)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1191)
 </small>
 
 **What it does**
@@ -1198,7 +1262,7 @@ func()  # TypeError: func() missing 1 required positional argument: 'x'
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20no-matching-overload) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1111)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1210)
 </small>
 
 **What it does**
@@ -1225,7 +1289,7 @@ func("string")  # error: [no-matching-overload]
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20non-subscriptable) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1134)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1233)
 </small>
 
 **What it does**
@@ -1247,7 +1311,7 @@ Subscripting an object that does not support it will raise a `TypeError` at runt
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20not-iterable) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1152)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1251)
 </small>
 
 **What it does**
@@ -1271,7 +1335,7 @@ for i in 34:  # TypeError: 'int' object is not iterable
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20parameter-already-assigned) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1203)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1302)
 </small>
 
 **What it does**
@@ -1325,7 +1389,7 @@ def test(): -> "int":
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20static-assert-error) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1539)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1638)
 </small>
 
 **What it does**
@@ -1353,7 +1417,7 @@ static_assert(int(2.0 * 3.0) == 6)  # error: does not have a statically known tr
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20subclass-of-final-class) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1294)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1393)
 </small>
 
 **What it does**
@@ -1380,7 +1444,7 @@ class B(A): ...  # Error raised here
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20too-many-positional-arguments) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1339)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1438)
 </small>
 
 **What it does**
@@ -1405,7 +1469,7 @@ f("foo")  # Error raised here
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20type-assertion-failure) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1317)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1416)
 </small>
 
 **What it does**
@@ -1431,7 +1495,7 @@ def _(x: int):
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unavailable-implicit-super-arguments) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1360)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1459)
 </small>
 
 **What it does**
@@ -1475,7 +1539,7 @@ class A:
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unknown-argument) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1417)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1516)
 </small>
 
 **What it does**
@@ -1500,7 +1564,7 @@ f(x=1, y=2)  # Error raised here
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unresolved-attribute) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1438)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1537)
 </small>
 
 **What it does**
@@ -1526,7 +1590,7 @@ A().foo  # AttributeError: 'A' object has no attribute 'foo'
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unresolved-import) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1460)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1559)
 </small>
 
 **What it does**
@@ -1549,7 +1613,7 @@ import foo  # ModuleNotFoundError: No module named 'foo'
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unresolved-reference) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1479)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1578)
 </small>
 
 **What it does**
@@ -1572,7 +1636,7 @@ print(x)  # NameError: name 'x' is not defined
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unsupported-bool-conversion) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1172)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1271)
 </small>
 
 **What it does**
@@ -1607,7 +1671,7 @@ b1 < b2 < b1  # exception raised here
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unsupported-operator) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1498)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1597)
 </small>
 
 **What it does**
@@ -1633,7 +1697,7 @@ A() + A()  # TypeError: unsupported operand type(s) for +: 'A' and 'A'
 <small>
 Default level: [`error`](../rules.md#rule-levels "This lint has a default level of 'error'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20zero-stepsize-in-slice) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1520)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1619)
 </small>
 
 **What it does**
@@ -1651,12 +1715,51 @@ l = list(range(10))
 l[1:10:0]  # ValueError: slice step cannot be zero
 ```
 
+## `ambiguous-protocol-member`
+
+<small>
+Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
+[Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20ambiguous-protocol-member) ·
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L458)
+</small>
+
+**What it does**
+
+Checks for protocol classes with members that will lead to ambiguous interfaces.
+
+**Why is this bad?**
+
+Assigning to an undeclared variable in a protocol class leads to an ambiguous
+interface which may lead to the type checker inferring unexpected things. It's
+recommended to ensure that all members of a protocol class are explicitly declared.
+
+**Examples**
+
+
+```py
+from typing import Protocol
+
+class BaseProto(Protocol):
+    a: int                               # fine (explicitly declared as `int`)
+    def method_member(self) -> int: ...  # fine: a method definition using `def` is considered a declaration
+    c = "some variable"                  # error: no explicit declaration, leading to ambiguity
+    b = method_member                    # error: no explicit declaration, leading to ambiguity
+
+    # error: this creates implicit assignments of `d` and `e` in the protocol class body.
+    # Were they really meant to be considered protocol members?
+    for d, e in enumerate(range(42)):
+        pass
+
+class SubProto(BaseProto, Protocol):
+    a = 42  # fine (declared in superclass)
+```
+
 ## `deprecated`
 
 <small>
 Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20deprecated) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L266)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L274)
 </small>
 
 **What it does**
@@ -1709,7 +1812,7 @@ a = 20 / 0  # type: ignore
 <small>
 Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-unbound-attribute) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1224)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1323)
 </small>
 
 **What it does**
@@ -1735,7 +1838,7 @@ A.c  # AttributeError: type object 'A' has no attribute 'c'
 <small>
 Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-unbound-implicit-call) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L119)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L127)
 </small>
 
 **What it does**
@@ -1765,7 +1868,7 @@ A()[0]  # TypeError: 'A' object is not subscriptable
 <small>
 Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-unbound-import) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1246)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1345)
 </small>
 
 **What it does**
@@ -1795,7 +1898,7 @@ from module import a  # ImportError: cannot import name 'a' from 'module'
 <small>
 Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20redundant-cast) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1591)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1690)
 </small>
 
 **What it does**
@@ -1820,7 +1923,7 @@ cast(int, f())  # Redundant
 <small>
 Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20undefined-reveal) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1399)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1498)
 </small>
 
 **What it does**
@@ -1871,7 +1974,7 @@ a = 20 / 0  # ty: ignore[division-by-zero]
 <small>
 Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unresolved-global) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1612)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1711)
 </small>
 
 **What it does**
@@ -1925,7 +2028,7 @@ def g():
 <small>
 Default level: [`warn`](../rules.md#rule-levels "This lint has a default level of 'warn'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20unsupported-base) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L599)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L698)
 </small>
 
 **What it does**
@@ -1962,7 +2065,7 @@ class D(C): ...  # error: [unsupported-base]
 <small>
 Default level: [`ignore`](../rules.md#rule-levels "This lint has a default level of 'ignore'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20division-by-zero) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L248)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L256)
 </small>
 
 **What it does**
@@ -1984,7 +2087,7 @@ Dividing by zero raises a `ZeroDivisionError` at runtime.
 <small>
 Default level: [`ignore`](../rules.md#rule-levels "This lint has a default level of 'ignore'.") ·
 [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-unresolved-reference) ·
-[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1272)
+[View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1371)
 </small>
 
 **What it does**

crates/ty/src/lib.rs

@@ -62,6 +62,10 @@ pub(crate) fn version() -> Result<()> {
 }
 
 fn run_check(args: CheckCommand) -> anyhow::Result<ExitStatus> {
+    // Enabled ANSI colors on Windows 10.
+    #[cfg(windows)]
+    assert!(colored::control::set_virtual_terminal(true).is_ok());
+
     set_colored_override(args.color);
 
     let verbosity = args.verbosity.level();

crates/ty/tests/cli/python_environment.rs

@@ -345,6 +345,51 @@ import bar",
     Ok(())
 }
 
+/// On Unix systems, a virtual environment can come with multiple `site-packages` directories:
+/// one at `<sys.prefix>/lib/pythonX.Y/site-packages` and one at
+/// `<sys.prefix>/lib64/pythonX.Y/site-packages`. According to [the stdlib docs], the `lib64`
+/// is not *meant* to have any Python files in it (only C extensions and similar). Empirically,
+/// however, it sometimes does indeed have Python files in it: popular tools such as poetry
+/// appear to sometimes install Python packages into the `lib64` site-packages directory even
+/// though they probably shouldn't. We therefore check for both a `lib64` and a `lib` directory,
+/// and add them both as search paths if they both exist.
+///
+/// See:
+/// - <https://github.com/astral-sh/ty/issues/1043>
+/// - <https://github.com/astral-sh/ty/issues/257>.
+///
+/// [the stdlib docs]: https://docs.python.org/3/library/sys.html#sys.platlibdir
+#[cfg(unix)]
+#[test]
+fn lib64_site_packages_directory_on_unix() -> anyhow::Result<()> {
+    let case = CliTest::with_files([
+        (".venv/lib/python3.13/site-packages/foo.py", ""),
+        (".venv/lib64/python3.13/site-packages/bar.py", ""),
+        ("test.py", "import foo, bar, baz"),
+    ])?;
+
+    assert_cmd_snapshot!(case.command().arg("--python").arg(".venv"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Cannot resolve imported module `baz`
+     --> test.py:1:18
+      |
+    1 | import foo, bar, baz
+      |                  ^^^
+      |
+    info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    Ok(())
+}
+
 #[test]
 fn pyvenv_cfg_file_annotation_showing_where_python_version_set() -> anyhow::Result<()> {
     let case = CliTest::with_files([
@@ -762,7 +807,7 @@ fn unix_system_installation_with_no_lib_directory() -> anyhow::Result<()> {
     WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
     ty failed
       Cause: Failed to discover the site-packages directory
-      Cause: Failed to iterate over the contents of the `lib` directory of the Python installation
+      Cause: Failed to iterate over the contents of the `lib`/`lib64` directories of the Python installation
 
     --> Invalid setting in configuration file `<temp_dir>/pyproject.toml`
       |
@@ -771,8 +816,6 @@ fn unix_system_installation_with_no_lib_directory() -> anyhow::Result<()> {
     3 | python = "directory-but-no-site-packages"
       |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       |
-
-      Cause: No such file or directory (os error 2)
     "#);
 
     Ok(())
@@ -857,59 +900,165 @@ fn defaults_to_a_new_python_version() -> anyhow::Result<()> {
 /// The `site-packages` directory is used by ty for external import.
 /// Ty does the following checks to discover the `site-packages` directory in the order:
 /// 1) If `VIRTUAL_ENV` environment variable is set
-/// 2) If `CONDA_PREFIX` environment variable is set
+/// 2) If `CONDA_PREFIX` environment variable is set (and .filename != `CONDA_DEFAULT_ENV`)
 /// 3) If a `.venv` directory exists at the project root
+/// 4) If `CONDA_PREFIX` environment variable is set (and .filename == `CONDA_DEFAULT_ENV`)
 ///
-/// This test is aiming at validating the logic around `CONDA_PREFIX`.
+/// This test (and the next one) is aiming at validating the logic around these cases.
 ///
-/// A conda-like environment file structure is used
-/// We test by first not setting the `CONDA_PREFIX` and expect a fail.
-/// Then we test by setting `CONDA_PREFIX` to `conda-env` and expect a pass.
+/// To do this we create a program that has these 4 imports:
+///
+/// ```python
+/// from package1 import ActiveVenv
+/// from package1 import ChildConda
+/// from package1 import WorkingVenv
+/// from package1 import BaseConda
+/// ```
+///
+/// We then create 4 different copies of package1. Each copy defines all of these
+/// classes... except the one that describes it. Therefore we know we got e.g.
+/// the working venv if we get a diagnostic like this:
+///
+/// ```text
+/// Unresolved import
+/// 4 | from package1 import WorkingVenv
+///   |                      ^^^^^^^^^^^
+/// ```
+///
+/// This test uses a directory structure as follows:
 ///
 /// ├── project
-/// │   └── test.py
-/// └── conda-env
-///     └── lib
-///         └── python3.13
-///             └── site-packages
-///                 └── package1
-///                     └── __init__.py
+/// │   ├── test.py
+/// │   └── .venv
+/// │       ├── pyvenv.cfg
+/// │       └── lib
+/// │           └── python3.13
+/// │               └── site-packages
+/// │                   └── package1
+/// │                       └── __init__.py
+/// ├── myvenv
+/// │   ├── pyvenv.cfg
+/// │   └── lib
+/// │       └── python3.13
+/// │           └── site-packages
+/// │               └── package1
+/// │                   └── __init__.py
+/// ├── conda-env
+/// │   └── lib
+/// │       └── python3.13
+/// │           └── site-packages
+/// │               └── package1
+/// │                   └── __init__.py
+/// └── conda
+///     └── envs
+///         └── base
+///             └── lib
+///                 └── python3.13
+///                     └── site-packages
+///                         └── package1
+///                             └── __init__.py
 ///
 /// test.py imports package1
 /// And the command is run in the `child` directory.
 #[test]
-fn check_conda_prefix_var_to_resolve_path() -> anyhow::Result<()> {
-    let conda_package1_path = if cfg!(windows) {
+fn check_venv_resolution_with_working_venv() -> anyhow::Result<()> {
+    let child_conda_package1_path = if cfg!(windows) {
         "conda-env/Lib/site-packages/package1/__init__.py"
     } else {
         "conda-env/lib/python3.13/site-packages/package1/__init__.py"
     };
 
+    let base_conda_package1_path = if cfg!(windows) {
+        "conda/envs/base/Lib/site-packages/package1/__init__.py"
+    } else {
+        "conda/envs/base/lib/python3.13/site-packages/package1/__init__.py"
+    };
+
+    let working_venv_package1_path = if cfg!(windows) {
+        "project/.venv/Lib/site-packages/package1/__init__.py"
+    } else {
+        "project/.venv/lib/python3.13/site-packages/package1/__init__.py"
+    };
+
+    let active_venv_package1_path = if cfg!(windows) {
+        "myvenv/Lib/site-packages/package1/__init__.py"
+    } else {
+        "myvenv/lib/python3.13/site-packages/package1/__init__.py"
+    };
+
     let case = CliTest::with_files([
         (
             "project/test.py",
             r#"
-            import package1
+            from package1 import ActiveVenv
+            from package1 import ChildConda
+            from package1 import WorkingVenv
+            from package1 import BaseConda
             "#,
         ),
         (
-            conda_package1_path,
+            "project/.venv/pyvenv.cfg",
             r#"
+home = ./
+
+            "#,
+        ),
+        (
+            "myvenv/pyvenv.cfg",
+            r#"
+home = ./
+
+            "#,
+        ),
+        (
+            active_venv_package1_path,
+            r#"
+            class ChildConda: ...
+            class WorkingVenv: ...
+            class BaseConda: ...
+            "#,
+        ),
+        (
+            child_conda_package1_path,
+            r#"
+            class ActiveVenv: ...
+            class WorkingVenv: ...
+            class BaseConda: ...
+            "#,
+        ),
+        (
+            working_venv_package1_path,
+            r#"
+            class ActiveVenv: ...
+            class ChildConda: ...
+            class BaseConda: ...
+            "#,
+        ),
+        (
+            base_conda_package1_path,
+            r#"
+            class ActiveVenv: ...
+            class ChildConda: ...
+            class WorkingVenv: ...
             "#,
         ),
     ])?;
 
-    assert_cmd_snapshot!(case.command().current_dir(case.root().join("project")), @r"
+    // Run with nothing set, should find the working venv
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project")), @r"
     success: false
     exit_code: 1
     ----- stdout -----
-    error[unresolved-import]: Cannot resolve imported module `package1`
-     --> test.py:2:8
+    error[unresolved-import]: Module `package1` has no member `WorkingVenv`
+     --> test.py:4:22
       |
-    2 | import package1
-      |        ^^^^^^^^
+    2 | from package1 import ActiveVenv
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+      |                      ^^^^^^^^^^^
+    5 | from package1 import BaseConda
       |
-    info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
     info: rule `unresolved-import` is enabled by default
 
     Found 1 diagnostic
@@ -918,12 +1067,373 @@ fn check_conda_prefix_var_to_resolve_path() -> anyhow::Result<()> {
     WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
     ");
 
-    // do command : CONDA_PREFIX=<temp_dir>/conda_env
-    assert_cmd_snapshot!(case.command().current_dir(case.root().join("project")).env("CONDA_PREFIX", case.root().join("conda-env")), @r"
-    success: true
-    exit_code: 0
+    // Run with VIRTUAL_ENV set, should find the active venv
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("VIRTUAL_ENV", case.root().join("myvenv")), @r"
+    success: false
+    exit_code: 1
     ----- stdout -----
-    All checks passed!
+    error[unresolved-import]: Module `package1` has no member `ActiveVenv`
+     --> test.py:2:22
+      |
+    2 | from package1 import ActiveVenv
+      |                      ^^^^^^^^^^
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // run with CONDA_PREFIX set, should find the child conda
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("CONDA_PREFIX", case.root().join("conda-env")), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `ChildConda`
+     --> test.py:3:22
+      |
+    2 | from package1 import ActiveVenv
+    3 | from package1 import ChildConda
+      |                      ^^^^^^^^^^
+    4 | from package1 import WorkingVenv
+    5 | from package1 import BaseConda
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // run with CONDA_PREFIX and CONDA_DEFAULT_ENV set (unequal), should find child conda
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("CONDA_PREFIX", case.root().join("conda-env"))
+        .env("CONDA_DEFAULT_ENV", "base"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `ChildConda`
+     --> test.py:3:22
+      |
+    2 | from package1 import ActiveVenv
+    3 | from package1 import ChildConda
+      |                      ^^^^^^^^^^
+    4 | from package1 import WorkingVenv
+    5 | from package1 import BaseConda
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // run with CONDA_PREFIX and CONDA_DEFAULT_ENV (unequal) and VIRTUAL_ENV set,
+    // should find child active venv
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("CONDA_PREFIX", case.root().join("conda-env"))
+        .env("CONDA_DEFAULT_ENV", "base")
+        .env("VIRTUAL_ENV", case.root().join("myvenv")), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `ActiveVenv`
+     --> test.py:2:22
+      |
+    2 | from package1 import ActiveVenv
+      |                      ^^^^^^^^^^
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // run with CONDA_PREFIX and CONDA_DEFAULT_ENV (equal!) set, should find working venv
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("CONDA_PREFIX", case.root().join("conda/envs/base"))
+        .env("CONDA_DEFAULT_ENV", "base"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `WorkingVenv`
+     --> test.py:4:22
+      |
+    2 | from package1 import ActiveVenv
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+      |                      ^^^^^^^^^^^
+    5 | from package1 import BaseConda
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    Ok(())
+}
+
+/// The exact same test as above, but without a working venv
+///
+/// In this case the Base Conda should be a possible outcome.
+#[test]
+fn check_venv_resolution_without_working_venv() -> anyhow::Result<()> {
+    let child_conda_package1_path = if cfg!(windows) {
+        "conda-env/Lib/site-packages/package1/__init__.py"
+    } else {
+        "conda-env/lib/python3.13/site-packages/package1/__init__.py"
+    };
+
+    let base_conda_package1_path = if cfg!(windows) {
+        "conda/envs/base/Lib/site-packages/package1/__init__.py"
+    } else {
+        "conda/envs/base/lib/python3.13/site-packages/package1/__init__.py"
+    };
+
+    let active_venv_package1_path = if cfg!(windows) {
+        "myvenv/Lib/site-packages/package1/__init__.py"
+    } else {
+        "myvenv/lib/python3.13/site-packages/package1/__init__.py"
+    };
+
+    let case = CliTest::with_files([
+        (
+            "project/test.py",
+            r#"
+            from package1 import ActiveVenv
+            from package1 import ChildConda
+            from package1 import WorkingVenv
+            from package1 import BaseConda
+            "#,
+        ),
+        (
+            "myvenv/pyvenv.cfg",
+            r#"
+home = ./
+
+            "#,
+        ),
+        (
+            active_venv_package1_path,
+            r#"
+            class ChildConda: ...
+            class WorkingVenv: ...
+            class BaseConda: ...
+            "#,
+        ),
+        (
+            child_conda_package1_path,
+            r#"
+            class ActiveVenv: ...
+            class WorkingVenv: ...
+            class BaseConda: ...
+            "#,
+        ),
+        (
+            base_conda_package1_path,
+            r#"
+            class ActiveVenv: ...
+            class ChildConda: ...
+            class WorkingVenv: ...
+            "#,
+        ),
+    ])?;
+
+    // Run with nothing set, should fail to find anything
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project")), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Cannot resolve imported module `package1`
+     --> test.py:2:6
+      |
+    2 | from package1 import ActiveVenv
+      |      ^^^^^^^^
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+      |
+    info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
+    info: rule `unresolved-import` is enabled by default
+
+    error[unresolved-import]: Cannot resolve imported module `package1`
+     --> test.py:3:6
+      |
+    2 | from package1 import ActiveVenv
+    3 | from package1 import ChildConda
+      |      ^^^^^^^^
+    4 | from package1 import WorkingVenv
+    5 | from package1 import BaseConda
+      |
+    info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
+    info: rule `unresolved-import` is enabled by default
+
+    error[unresolved-import]: Cannot resolve imported module `package1`
+     --> test.py:4:6
+      |
+    2 | from package1 import ActiveVenv
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+      |      ^^^^^^^^
+    5 | from package1 import BaseConda
+      |
+    info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
+    info: rule `unresolved-import` is enabled by default
+
+    error[unresolved-import]: Cannot resolve imported module `package1`
+     --> test.py:5:6
+      |
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+    5 | from package1 import BaseConda
+      |      ^^^^^^^^
+      |
+    info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
+    info: rule `unresolved-import` is enabled by default
+
+    Found 4 diagnostics
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // Run with VIRTUAL_ENV set, should find the active venv
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("VIRTUAL_ENV", case.root().join("myvenv")), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `ActiveVenv`
+     --> test.py:2:22
+      |
+    2 | from package1 import ActiveVenv
+      |                      ^^^^^^^^^^
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // run with CONDA_PREFIX set, should find the child conda
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("CONDA_PREFIX", case.root().join("conda-env")), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `ChildConda`
+     --> test.py:3:22
+      |
+    2 | from package1 import ActiveVenv
+    3 | from package1 import ChildConda
+      |                      ^^^^^^^^^^
+    4 | from package1 import WorkingVenv
+    5 | from package1 import BaseConda
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // run with CONDA_PREFIX and CONDA_DEFAULT_ENV set (unequal), should find child conda
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("CONDA_PREFIX", case.root().join("conda-env"))
+        .env("CONDA_DEFAULT_ENV", "base"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `ChildConda`
+     --> test.py:3:22
+      |
+    2 | from package1 import ActiveVenv
+    3 | from package1 import ChildConda
+      |                      ^^^^^^^^^^
+    4 | from package1 import WorkingVenv
+    5 | from package1 import BaseConda
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // run with CONDA_PREFIX and CONDA_DEFAULT_ENV (unequal) and VIRTUAL_ENV set,
+    // should find child active venv
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("CONDA_PREFIX", case.root().join("conda-env"))
+        .env("CONDA_DEFAULT_ENV", "base")
+        .env("VIRTUAL_ENV", case.root().join("myvenv")), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `ActiveVenv`
+     --> test.py:2:22
+      |
+    2 | from package1 import ActiveVenv
+      |                      ^^^^^^^^^^
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
+
+    ----- stderr -----
+    WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
+    ");
+
+    // run with CONDA_PREFIX and CONDA_DEFAULT_ENV (equal!) set, should find base conda
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("CONDA_PREFIX", case.root().join("conda/envs/base"))
+        .env("CONDA_DEFAULT_ENV", "base"), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    error[unresolved-import]: Module `package1` has no member `BaseConda`
+     --> test.py:5:22
+      |
+    3 | from package1 import ChildConda
+    4 | from package1 import WorkingVenv
+    5 | from package1 import BaseConda
+      |                      ^^^^^^^^^
+      |
+    info: rule `unresolved-import` is enabled by default
+
+    Found 1 diagnostic
 
     ----- stderr -----
     WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.

crates/ty_ide/src/completion.rs

@@ -23,7 +23,18 @@ pub fn completion(db: &dyn Db, file: File, offset: TextSize) -> Vec<Completion<'
     let model = SemanticModel::new(db, file);
     let mut completions = match target {
         CompletionTargetAst::ObjectDot { expr } => model.attribute_completions(expr),
-        CompletionTargetAst::ImportFrom { import, name } => model.import_completions(import, name),
+        CompletionTargetAst::ObjectDotInImport { import, name } => {
+            model.import_submodule_completions(import, name)
+        }
+        CompletionTargetAst::ObjectDotInImportFrom { import } => {
+            model.from_import_submodule_completions(import)
+        }
+        CompletionTargetAst::ImportFrom { import, name } => {
+            model.from_import_completions(import, name)
+        }
+        CompletionTargetAst::Import { .. } | CompletionTargetAst::ImportViaFrom { .. } => {
+            model.import_completions()
+        }
         CompletionTargetAst::Scoped { node } => model.scoped_completions(node),
     };
     completions.sort_by(compare_suggestions);
@@ -50,11 +61,11 @@ enum CompletionTargetTokens<'t> {
         object: &'t Token,
         /// The token, if non-empty, following the dot.
         ///
-        /// This is currently unused, but we should use this
-        /// eventually to remove completions that aren't a
-        /// prefix of what has already been typed. (We are
-        /// currently relying on the LSP client to do this.)
-        #[expect(dead_code)]
+        /// For right now, this is only used to determine which
+        /// module in an `import` statement to return submodule
+        /// completions for. But we could use it for other things,
+        /// like only returning completions that start with a prefix
+        /// corresponding to this token.
         attribute: Option<&'t Token>,
     },
     /// A `from module import attribute` token form was found, where
@@ -63,6 +74,20 @@ enum CompletionTargetTokens<'t> {
         /// The module being imported from.
         module: &'t Token,
     },
+    /// A `import module` token form was found, where `module` may be
+    /// empty.
+    Import {
+        /// The token corresponding to the `import` keyword.
+        import: &'t Token,
+        /// The token closest to the cursor.
+        ///
+        /// This is currently unused, but we should use this
+        /// eventually to remove completions that aren't a
+        /// prefix of what has already been typed. (We are
+        /// currently relying on the LSP client to do this.)
+        #[expect(dead_code)]
+        module: &'t Token,
+    },
     /// A token was found under the cursor, but it didn't
     /// match any of our anticipated token patterns.
     Generic { token: &'t Token },
@@ -105,6 +130,8 @@ impl<'t> CompletionTargetTokens<'t> {
                 }
             } else if let Some(module) = import_from_tokens(before) {
                 CompletionTargetTokens::ImportFrom { module }
+            } else if let Some((import, module)) = import_tokens(before) {
+                CompletionTargetTokens::Import { import, module }
             } else if let Some([_]) = token_suffix_by_kinds(before, [TokenKind::Float]) {
                 // If we're writing a `float`, then we should
                 // specifically not offer completions. This wouldn't
@@ -140,19 +167,47 @@ impl<'t> CompletionTargetTokens<'t> {
         offset: TextSize,
     ) -> Option<CompletionTargetAst<'t>> {
         match *self {
-            CompletionTargetTokens::PossibleObjectDot { object, .. } => {
+            CompletionTargetTokens::PossibleObjectDot { object, attribute } => {
                 let covering_node = covering_node(parsed.syntax().into(), object.range())
-                    // We require that the end of the node range not
-                    // exceed the cursor offset. This avoids selecting
-                    // a node "too high" in the AST in cases where
-                    // completions are requested in the middle of an
-                    // expression. e.g., `foo.<CURSOR>.bar`.
-                    .find_last(|node| node.is_expr_attribute() && node.range().end() <= offset)
+                    .find_last(|node| {
+                        // We require that the end of the node range not
+                        // exceed the cursor offset. This avoids selecting
+                        // a node "too high" in the AST in cases where
+                        // completions are requested in the middle of an
+                        // expression. e.g., `foo.<CURSOR>.bar`.
+                        if node.is_expr_attribute() {
+                            return node.range().end() <= offset;
+                        }
+                        // For import statements though, they can't be
+                        // nested, so we don't care as much about the
+                        // cursor being strictly after the statement.
+                        // And indeed, sometimes it won't be! e.g.,
+                        //
+                        //   import re, os.p<CURSOR>, zlib
+                        //
+                        // So just return once we find an import.
+                        node.is_stmt_import() || node.is_stmt_import_from()
+                    })
                     .ok()?;
                 match covering_node.node() {
                     ast::AnyNodeRef::ExprAttribute(expr) => {
                         Some(CompletionTargetAst::ObjectDot { expr })
                     }
+                    ast::AnyNodeRef::StmtImport(import) => {
+                        let range = attribute
+                            .map(Ranged::range)
+                            .unwrap_or_else(|| object.range());
+                        // Find the name that overlaps with the
+                        // token we identified for the attribute.
+                        let name = import
+                            .names
+                            .iter()
+                            .position(|alias| alias.range().contains_range(range))?;
+                        Some(CompletionTargetAst::ObjectDotInImport { import, name })
+                    }
+                    ast::AnyNodeRef::StmtImportFrom(import) => {
+                        Some(CompletionTargetAst::ObjectDotInImportFrom { import })
+                    }
                     _ => None,
                 }
             }
@@ -165,6 +220,20 @@ impl<'t> CompletionTargetTokens<'t> {
                 };
                 Some(CompletionTargetAst::ImportFrom { import, name: None })
             }
+            CompletionTargetTokens::Import { import, .. } => {
+                let covering_node = covering_node(parsed.syntax().into(), import.range())
+                    .find_first(|node| node.is_stmt_import() || node.is_stmt_import_from())
+                    .ok()?;
+                match covering_node.node() {
+                    ast::AnyNodeRef::StmtImport(import) => {
+                        Some(CompletionTargetAst::Import { import, name: None })
+                    }
+                    ast::AnyNodeRef::StmtImportFrom(import) => {
+                        Some(CompletionTargetAst::ImportViaFrom { import })
+                    }
+                    _ => None,
+                }
+            }
             CompletionTargetTokens::Generic { token } => {
                 let covering_node = covering_node(parsed.syntax().into(), token.range());
                 Some(CompletionTargetAst::Scoped {
@@ -188,6 +257,18 @@ enum CompletionTargetAst<'t> {
     /// A `object.attribute` scenario, where we want to
     /// list attributes on `object` for completions.
     ObjectDot { expr: &'t ast::ExprAttribute },
+    /// A `import module.submodule` scenario, where we only want to
+    /// list submodules for completions.
+    ObjectDotInImport {
+        /// The import statement.
+        import: &'t ast::StmtImport,
+        /// An index into `import.names`. The index is guaranteed to be
+        /// valid.
+        name: usize,
+    },
+    /// A `from module.submodule` scenario, where we only want to list
+    /// submodules for completions.
+    ObjectDotInImportFrom { import: &'t ast::StmtImportFrom },
     /// A `from module import attribute` scenario, where we want to
     /// list attributes on `module` for completions.
     ImportFrom {
@@ -197,6 +278,24 @@ enum CompletionTargetAst<'t> {
         /// set, the index is guaranteed to be valid.
         name: Option<usize>,
     },
+    /// A `import module` scenario, where we want to
+    /// list available modules for completions.
+    Import {
+        /// The import statement.
+        #[expect(dead_code)]
+        import: &'t ast::StmtImport,
+        /// An index into `import.names` if relevant. When this is
+        /// set, the index is guaranteed to be valid.
+        #[expect(dead_code)]
+        name: Option<usize>,
+    },
+    /// A `from module` scenario, where we want to
+    /// list available modules for completions.
+    ImportViaFrom {
+        /// The import statement.
+        #[expect(dead_code)]
+        import: &'t ast::StmtImportFrom,
+    },
     /// A scoped scenario, where we want to list all items available in
     /// the most narrow scope containing the giving AST node.
     Scoped { node: ast::AnyNodeRef<'t> },
@@ -317,6 +416,52 @@ fn import_from_tokens(tokens: &[Token]) -> Option<&Token> {
     None
 }
 
+/// Looks for the start of a `import <CURSOR>` statement.
+///
+/// This also handles cases like `import foo, c<CURSOR>, bar`.
+///
+/// If found, a token corresponding to the `import` or `from` keyword
+/// and the the closest point of the `<CURSOR>` is returned.
+///
+/// It is assumed that callers will call `from_import_tokens` first to
+/// try and recognize a `from ... import ...` statement before using
+/// this.
+fn import_tokens(tokens: &[Token]) -> Option<(&Token, &Token)> {
+    use TokenKind as TK;
+
+    /// A look-back limit, in order to bound work.
+    ///
+    /// See `LIMIT` in `import_from_tokens` for more context.
+    const LIMIT: usize = 1_000;
+
+    /// A state used to "parse" the tokens preceding the user's cursor,
+    /// in reverse, to detect a `import` statement.
+    enum S {
+        Start,
+        Names,
+    }
+
+    let mut state = S::Start;
+    let module_token = tokens.last()?;
+    // Move backward through the tokens until we get to
+    // the `import` token.
+    for token in tokens.iter().rev().take(LIMIT) {
+        state = match (state, token.kind()) {
+            // It's okay to pop off a newline token here initially,
+            // since it may occur when the name being imported is
+            // empty.
+            (S::Start, TK::Newline) => S::Names,
+            // Munch through tokens that can make up an alias.
+            (S::Start | S::Names, TK::Name | TK::Comma | TK::As | TK::Unknown) => S::Names,
+            (S::Start | S::Names, TK::Import | TK::From) => {
+                return Some((token, module_token));
+            }
+            _ => return None,
+        };
+    }
+    None
+}
+
 /// Order completions lexicographically, with these exceptions:
 ///
 /// 1) A `_[^_]` prefix sorts last and
@@ -1247,7 +1392,7 @@ quux.<CURSOR>
         __init_subclass__ :: bound method Quux.__init_subclass__() -> None
         __module__ :: str
         __ne__ :: bound method Quux.__ne__(value: object, /) -> bool
-        __new__ :: bound method Quux.__new__() -> Self@__new__
+        __new__ :: bound method Quux.__new__() -> Quux
         __reduce__ :: bound method Quux.__reduce__() -> str | tuple[Any, ...]
         __reduce_ex__ :: bound method Quux.__reduce_ex__(protocol: SupportsIndex, /) -> str | tuple[Any, ...]
         __repr__ :: bound method Quux.__repr__() -> str
@@ -1292,7 +1437,7 @@ quux.b<CURSOR>
         __init_subclass__ :: bound method Quux.__init_subclass__() -> None
         __module__ :: str
         __ne__ :: bound method Quux.__ne__(value: object, /) -> bool
-        __new__ :: bound method Quux.__new__() -> Self@__new__
+        __new__ :: bound method Quux.__new__() -> Quux
         __reduce__ :: bound method Quux.__reduce__() -> str | tuple[Any, ...]
         __reduce_ex__ :: bound method Quux.__reduce_ex__(protocol: SupportsIndex, /) -> str | tuple[Any, ...]
         __repr__ :: bound method Quux.__repr__() -> str
@@ -2262,7 +2407,11 @@ import fo<CURSOR>
 ",
         );
 
-        assert_snapshot!(test.completions_without_builtins(), @"<No completions found>");
+        // This snapshot would generate a big list of modules,
+        // which is kind of annoying. So just assert that it
+        // runs without panicking and produces some non-empty
+        // output.
+        assert!(!test.completions_without_builtins().is_empty());
     }
 
     // Ref: https://github.com/astral-sh/ty/issues/572
@@ -2274,7 +2423,11 @@ import foo as ba<CURSOR>
 ",
         );
 
-        assert_snapshot!(test.completions_without_builtins(), @"<No completions found>");
+        // This snapshot would generate a big list of modules,
+        // which is kind of annoying. So just assert that it
+        // runs without panicking and produces some non-empty
+        // output.
+        assert!(!test.completions_without_builtins().is_empty());
     }
 
     // Ref: https://github.com/astral-sh/ty/issues/572
@@ -2286,7 +2439,11 @@ from fo<CURSOR> import wat
 ",
         );
 
-        assert_snapshot!(test.completions_without_builtins(), @"<No completions found>");
+        // This snapshot would generate a big list of modules,
+        // which is kind of annoying. So just assert that it
+        // runs without panicking and produces some non-empty
+        // output.
+        assert!(!test.completions_without_builtins().is_empty());
     }
 
     // Ref: https://github.com/astral-sh/ty/issues/572
@@ -2697,6 +2854,143 @@ importlib.<CURSOR>
         test.assert_completions_include("resources");
     }
 
+    #[test]
+    fn import_with_leading_character() {
+        let test = cursor_test(
+            "\
+import c<CURSOR>
+",
+        );
+        test.assert_completions_include("collections");
+    }
+
+    #[test]
+    fn import_without_leading_character() {
+        let test = cursor_test(
+            "\
+import <CURSOR>
+",
+        );
+        test.assert_completions_include("collections");
+    }
+
+    #[test]
+    fn import_multiple() {
+        let test = cursor_test(
+            "\
+import re, c<CURSOR>, sys
+",
+        );
+        test.assert_completions_include("collections");
+    }
+
+    #[test]
+    fn import_with_aliases() {
+        let test = cursor_test(
+            "\
+import re as regexp, c<CURSOR>, sys as system
+",
+        );
+        test.assert_completions_include("collections");
+    }
+
+    #[test]
+    fn import_over_multiple_lines() {
+        let test = cursor_test(
+            "\
+import re as regexp, \\
+    c<CURSOR>, \\
+    sys as system
+",
+        );
+        test.assert_completions_include("collections");
+    }
+
+    #[test]
+    fn import_unknown_in_module() {
+        let test = cursor_test(
+            "\
+import ?, <CURSOR>
+",
+        );
+        test.assert_completions_include("collections");
+    }
+
+    #[test]
+    fn import_via_from_with_leading_character() {
+        let test = cursor_test(
+            "\
+from c<CURSOR>
+",
+        );
+        test.assert_completions_include("collections");
+    }
+
+    #[test]
+    fn import_via_from_without_leading_character() {
+        let test = cursor_test(
+            "\
+from <CURSOR>
+",
+        );
+        test.assert_completions_include("collections");
+    }
+
+    #[test]
+    fn import_statement_with_submodule_with_leading_character() {
+        let test = cursor_test(
+            "\
+import os.p<CURSOR>
+",
+        );
+        test.assert_completions_include("path");
+        test.assert_completions_do_not_include("abspath");
+    }
+
+    #[test]
+    fn import_statement_with_submodule_multiple() {
+        let test = cursor_test(
+            "\
+import re, os.p<CURSOR>, zlib
+",
+        );
+        test.assert_completions_include("path");
+        test.assert_completions_do_not_include("abspath");
+    }
+
+    #[test]
+    fn import_statement_with_submodule_without_leading_character() {
+        let test = cursor_test(
+            "\
+import os.<CURSOR>
+",
+        );
+        test.assert_completions_include("path");
+        test.assert_completions_do_not_include("abspath");
+    }
+
+    #[test]
+    fn import_via_from_with_submodule_with_leading_character() {
+        let test = cursor_test(
+            "\
+from os.p<CURSOR>
+",
+        );
+        test.assert_completions_include("path");
+        test.assert_completions_do_not_include("abspath");
+    }
+
+    #[test]
+    fn import_via_from_with_submodule_without_leading_character() {
+        let test = cursor_test(
+            "\
+from os.<CURSOR>
+",
+        );
+        test.assert_completions_include("path");
+        test.assert_completions_do_not_include("abspath");
+    }
+
     #[test]
     fn regression_test_issue_642() {
         // Regression test for https://github.com/astral-sh/ty/issues/642

crates/ty_ide/src/goto.rs

@@ -11,6 +11,7 @@ use ruff_db::parsed::ParsedModuleRef;
 use ruff_python_ast::{self as ast, AnyNodeRef};
 use ruff_python_parser::TokenKind;
 use ruff_text_size::{Ranged, TextRange, TextSize};
+use ty_python_semantic::HasDefinition;
 use ty_python_semantic::ImportAliasResolution;
 use ty_python_semantic::ResolvedDefinition;
 use ty_python_semantic::types::Type;
@@ -285,36 +286,24 @@ impl GotoTarget<'_> {
 
             // For already-defined symbols, they are their own definitions
             GotoTarget::FunctionDef(function) => {
-                let range = function.name.range;
-                Some(DefinitionsOrTargets::Targets(
-                    crate::NavigationTargets::single(NavigationTarget {
-                        file,
-                        focus_range: range,
-                        full_range: function.range(),
-                    }),
-                ))
+                let model = SemanticModel::new(db, file);
+                Some(DefinitionsOrTargets::Definitions(vec![
+                    ResolvedDefinition::Definition(function.definition(&model)),
+                ]))
             }
 
             GotoTarget::ClassDef(class) => {
-                let range = class.name.range;
-                Some(DefinitionsOrTargets::Targets(
-                    crate::NavigationTargets::single(NavigationTarget {
-                        file,
-                        focus_range: range,
-                        full_range: class.range(),
-                    }),
-                ))
+                let model = SemanticModel::new(db, file);
+                Some(DefinitionsOrTargets::Definitions(vec![
+                    ResolvedDefinition::Definition(class.definition(&model)),
+                ]))
             }
 
             GotoTarget::Parameter(parameter) => {
-                let range = parameter.name.range;
-                Some(DefinitionsOrTargets::Targets(
-                    crate::NavigationTargets::single(NavigationTarget {
-                        file,
-                        focus_range: range,
-                        full_range: parameter.range(),
-                    }),
-                ))
+                let model = SemanticModel::new(db, file);
+                Some(DefinitionsOrTargets::Definitions(vec![
+                    ResolvedDefinition::Definition(parameter.definition(&model)),
+                ]))
             }
 
             // For import aliases (offset within 'y' or 'z' in "from x import y as z")
@@ -376,14 +365,10 @@ impl GotoTarget<'_> {
 
             // For exception variables, they are their own definitions (like parameters)
             GotoTarget::ExceptVariable(except_handler) => {
-                if let Some(name) = &except_handler.name {
-                    let range = name.range;
-                    Some(DefinitionsOrTargets::Targets(
-                        crate::NavigationTargets::single(NavigationTarget::new(file, range)),
-                    ))
-                } else {
-                    None
-                }
+                let model = SemanticModel::new(db, file);
+                Some(DefinitionsOrTargets::Definitions(vec![
+                    ResolvedDefinition::Definition(except_handler.definition(&model)),
+                ]))
             }
 
             // For pattern match rest variables, they are their own definitions

crates/ty_ide/src/goto_definition.rs

@@ -181,6 +181,49 @@ def other_function(): ...
         "#);
     }
 
+    /// goto-definition on a function definition in a .pyi should go to the .py
+    #[test]
+    fn goto_definition_stub_map_function_def() {
+        let test = CursorTest::builder()
+            .source(
+                "mymodule.py",
+                r#"
+def my_function():
+    return "hello"
+
+def other_function():
+    return "other"
+"#,
+            )
+            .source(
+                "mymodule.pyi",
+                r#"
+def my_fun<CURSOR>ction(): ...
+
+def other_function(): ...
+"#,
+            )
+            .build();
+
+        assert_snapshot!(test.goto_definition(), @r#"
+        info[goto-definition]: Definition
+         --> mymodule.py:2:5
+          |
+        2 | def my_function():
+          |     ^^^^^^^^^^^
+        3 |     return "hello"
+          |
+        info: Source
+         --> mymodule.pyi:2:5
+          |
+        2 | def my_function(): ...
+          |     ^^^^^^^^^^^
+        3 |
+        4 | def other_function(): ...
+          |
+        "#);
+    }
+
     /// goto-definition on a function that's redefined many times in the impl .py
     ///
     /// Currently this yields all instances. There's an argument for only yielding
@@ -328,6 +371,53 @@ class MyOtherClass:
         ");
     }
 
+    /// goto-definition on a class def in a .pyi should go to the .py
+    #[test]
+    fn goto_definition_stub_map_class_def() {
+        let test = CursorTest::builder()
+            .source(
+                "mymodule.py",
+                r#"
+class MyClass:
+    def __init__(self, val):
+        self.val = val
+
+class MyOtherClass:
+    def __init__(self, val):
+        self.val = val + 1
+"#,
+            )
+            .source(
+                "mymodule.pyi",
+                r#"
+class MyCl<CURSOR>ass:
+    def __init__(self, val: bool): ...
+
+class MyOtherClass:
+    def __init__(self, val: bool): ...
+"#,
+            )
+            .build();
+
+        assert_snapshot!(test.goto_definition(), @r"
+        info[goto-definition]: Definition
+         --> mymodule.py:2:7
+          |
+        2 | class MyClass:
+          |       ^^^^^^^
+        3 |     def __init__(self, val):
+        4 |         self.val = val
+          |
+        info: Source
+         --> mymodule.pyi:2:7
+          |
+        2 | class MyClass:
+          |       ^^^^^^^
+        3 |     def __init__(self, val: bool): ...
+          |
+        ");
+    }
+
     /// goto-definition on a class init should go to the .py not the .pyi
     #[test]
     fn goto_definition_stub_map_class_init() {

crates/ty_ide/src/goto_references.rs

@@ -405,9 +405,7 @@ except ValueError as err:
 ",
         );
 
-        // Note: Currently only finds the declaration, not the usages
-        // This is because semantic analysis for except handler variables isn't fully implemented
-        assert_snapshot!(test.references(), @r###"
+        assert_snapshot!(test.references(), @r"
         info[references]: Reference 1
          --> main.py:4:29
           |
@@ -418,7 +416,37 @@ except ValueError as err:
         5 |     print(f'Error: {err}')
         6 |     return err
           |
-        "###);
+
+        info[references]: Reference 2
+         --> main.py:5:21
+          |
+        3 |     x = 1 / 0
+        4 | except ZeroDivisionError as err:
+        5 |     print(f'Error: {err}')
+          |                     ^^^
+        6 |     return err
+          |
+
+        info[references]: Reference 3
+         --> main.py:6:12
+          |
+        4 | except ZeroDivisionError as err:
+        5 |     print(f'Error: {err}')
+        6 |     return err
+          |            ^^^
+        7 |
+        8 | try:
+          |
+
+        info[references]: Reference 4
+          --> main.py:11:31
+           |
+         9 |     y = 2 / 0
+        10 | except ValueError as err:
+        11 |     print(f'Different error: {err}')
+           |                               ^^^
+           |
+        ");
     }
 
     #[test]

crates/ty_ide/src/goto_type_definition.rs

@@ -197,16 +197,16 @@ mod tests {
             "#,
         );
 
-        assert_snapshot!(test.goto_type_definition(), @r#"
+        assert_snapshot!(test.goto_type_definition(), @r###"
         info[goto-type-definition]: Type definition
-           --> stdlib/builtins.pyi:892:7
+           --> stdlib/builtins.pyi:901:7
             |
-        890 |     def __getitem__(self, key: int, /) -> str | int | None: ...
-        891 |
-        892 | class str(Sequence[str]):
+        899 |     def __getitem__(self, key: int, /) -> str | int | None: ...
+        900 |
+        901 | class str(Sequence[str]):
             |       ^^^
-        893 |     """str(object='') -> str
-        894 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
+        902 |     """str(object='') -> str
+        903 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
             |
         info: Source
          --> main.py:4:13
@@ -216,7 +216,7 @@ mod tests {
         4 |             a
           |             ^
           |
-        "#);
+        "###);
     }
     #[test]
     fn goto_type_of_expression_with_literal_node() {
@@ -226,16 +226,16 @@ mod tests {
             "#,
         );
 
-        assert_snapshot!(test.goto_type_definition(), @r#"
+        assert_snapshot!(test.goto_type_definition(), @r###"
         info[goto-type-definition]: Type definition
-           --> stdlib/builtins.pyi:892:7
+           --> stdlib/builtins.pyi:901:7
             |
-        890 |     def __getitem__(self, key: int, /) -> str | int | None: ...
-        891 |
-        892 | class str(Sequence[str]):
+        899 |     def __getitem__(self, key: int, /) -> str | int | None: ...
+        900 |
+        901 | class str(Sequence[str]):
             |       ^^^
-        893 |     """str(object='') -> str
-        894 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
+        902 |     """str(object='') -> str
+        903 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
             |
         info: Source
          --> main.py:2:22
@@ -243,7 +243,7 @@ mod tests {
         2 |             a: str = "test"
           |                      ^^^^^^
           |
-        "#);
+        "###);
     }
 
     #[test]
@@ -342,16 +342,16 @@ mod tests {
             "#,
         );
 
-        assert_snapshot!(test.goto_type_definition(), @r#"
+        assert_snapshot!(test.goto_type_definition(), @r###"
         info[goto-type-definition]: Type definition
-           --> stdlib/builtins.pyi:892:7
+           --> stdlib/builtins.pyi:901:7
             |
-        890 |     def __getitem__(self, key: int, /) -> str | int | None: ...
-        891 |
-        892 | class str(Sequence[str]):
+        899 |     def __getitem__(self, key: int, /) -> str | int | None: ...
+        900 |
+        901 | class str(Sequence[str]):
             |       ^^^
-        893 |     """str(object='') -> str
-        894 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
+        902 |     """str(object='') -> str
+        903 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
             |
         info: Source
          --> main.py:4:18
@@ -361,7 +361,7 @@ mod tests {
         4 |             test(a= "123")
           |                  ^
           |
-        "#);
+        "###);
     }
 
     #[test]
@@ -411,16 +411,16 @@ f(**kwargs<CURSOR>)
             "#,
         );
 
-        assert_snapshot!(test.goto_type_definition(), @r#"
+        assert_snapshot!(test.goto_type_definition(), @r###"
         info[goto-type-definition]: Type definition
-            --> stdlib/builtins.pyi:2890:7
+            --> stdlib/builtins.pyi:2901:7
              |
-        2888 |         """See PEP 585"""
-        2889 |
-        2890 | class dict(MutableMapping[_KT, _VT]):
+        2899 |         """See PEP 585"""
+        2900 |
+        2901 | class dict(MutableMapping[_KT, _VT]):
              |       ^^^^
-        2891 |     """dict() -> new empty dictionary
-        2892 |     dict(mapping) -> new dictionary initialized from a mapping object's
+        2902 |     """dict() -> new empty dictionary
+        2903 |     dict(mapping) -> new dictionary initialized from a mapping object's
              |
         info: Source
          --> main.py:6:5
@@ -430,7 +430,7 @@ f(**kwargs<CURSOR>)
         6 | f(**kwargs)
           |     ^^^^^^
           |
-        "#);
+        "###);
     }
 
     #[test]
@@ -442,16 +442,16 @@ f(**kwargs<CURSOR>)
             "#,
         );
 
-        assert_snapshot!(test.goto_type_definition(), @r#"
+        assert_snapshot!(test.goto_type_definition(), @r###"
         info[goto-type-definition]: Type definition
-           --> stdlib/builtins.pyi:892:7
+           --> stdlib/builtins.pyi:901:7
             |
-        890 |     def __getitem__(self, key: int, /) -> str | int | None: ...
-        891 |
-        892 | class str(Sequence[str]):
+        899 |     def __getitem__(self, key: int, /) -> str | int | None: ...
+        900 |
+        901 | class str(Sequence[str]):
             |       ^^^
-        893 |     """str(object='') -> str
-        894 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
+        902 |     """str(object='') -> str
+        903 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
             |
         info: Source
          --> main.py:3:17
@@ -460,7 +460,7 @@ f(**kwargs<CURSOR>)
         3 |                 a
           |                 ^
           |
-        "#);
+        "###);
     }
 
     #[test]
@@ -535,16 +535,16 @@ f(**kwargs<CURSOR>)
             "#,
         );
 
-        assert_snapshot!(test.goto_type_definition(), @r#"
+        assert_snapshot!(test.goto_type_definition(), @r###"
         info[goto-type-definition]: Type definition
-           --> stdlib/builtins.pyi:892:7
+           --> stdlib/builtins.pyi:901:7
             |
-        890 |     def __getitem__(self, key: int, /) -> str | int | None: ...
-        891 |
-        892 | class str(Sequence[str]):
+        899 |     def __getitem__(self, key: int, /) -> str | int | None: ...
+        900 |
+        901 | class str(Sequence[str]):
             |       ^^^
-        893 |     """str(object='') -> str
-        894 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
+        902 |     """str(object='') -> str
+        903 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
             |
         info: Source
          --> main.py:4:27
@@ -554,7 +554,7 @@ f(**kwargs<CURSOR>)
         4 |                     print(a)
           |                           ^
           |
-        "#);
+        "###);
     }
 
     #[test]
@@ -566,7 +566,7 @@ f(**kwargs<CURSOR>)
             "#,
         );
 
-        assert_snapshot!(test.goto_type_definition(), @r#"
+        assert_snapshot!(test.goto_type_definition(), @r###"
         info[goto-type-definition]: Type definition
            --> stdlib/types.pyi:922:11
             |
@@ -585,14 +585,14 @@ f(**kwargs<CURSOR>)
           |
 
         info[goto-type-definition]: Type definition
-           --> stdlib/builtins.pyi:892:7
+           --> stdlib/builtins.pyi:901:7
             |
-        890 |     def __getitem__(self, key: int, /) -> str | int | None: ...
-        891 |
-        892 | class str(Sequence[str]):
+        899 |     def __getitem__(self, key: int, /) -> str | int | None: ...
+        900 |
+        901 | class str(Sequence[str]):
             |       ^^^
-        893 |     """str(object='') -> str
-        894 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
+        902 |     """str(object='') -> str
+        903 |     str(bytes_or_buffer[, encoding[, errors]]) -> str
             |
         info: Source
          --> main.py:3:17
@@ -601,7 +601,7 @@ f(**kwargs<CURSOR>)
         3 |                 a
           |                 ^
           |
-        "#);
+        "###);
     }
 
     impl CursorTest {

crates/ty_ide/src/hover.rs

@@ -6,8 +6,8 @@ use ruff_db::parsed::parsed_module;
 use ruff_text_size::{Ranged, TextSize};
 use std::fmt;
 use std::fmt::Formatter;
-use ty_python_semantic::SemanticModel;
 use ty_python_semantic::types::Type;
+use ty_python_semantic::{DisplaySettings, SemanticModel};
 
 pub fn hover(db: &dyn Db, file: File, offset: TextSize) -> Option<RangedValue<Hover<'_>>> {
     let parsed = parsed_module(db, file).load(db);
@@ -135,7 +135,10 @@ impl fmt::Display for DisplayHoverContent<'_, '_> {
         match self.content {
             HoverContent::Type(ty) => self
                 .kind
-                .fenced_code_block(ty.display(self.db), "python")
+                .fenced_code_block(
+                    ty.display_with(self.db, DisplaySettings::default().multiline()),
+                    "python",
+                )
                 .fmt(f),
             HoverContent::Docstring(docstring) => docstring.render(self.kind).fmt(f),
         }
@@ -201,7 +204,10 @@ mod tests {
         );
 
         assert_snapshot!(test.hover(), @r"
-        def my_func(a, b) -> Unknown
+        def my_func(
+            a,
+            b
+        ) -> Unknown
         ---------------------------------------------
         This is such a great func!!
 
@@ -211,7 +217,10 @@ mod tests {
 
         ---------------------------------------------
         ```python
-        def my_func(a, b) -> Unknown
+        def my_func(
+            a,
+            b
+        ) -> Unknown
         ```
         ---
         ```text
@@ -237,6 +246,63 @@ mod tests {
         ");
     }
 
+    #[test]
+    fn hover_function_def() {
+        let test = cursor_test(
+            r#"
+        def my_fu<CURSOR>nc(a, b):
+            '''This is such a great func!!
+
+            Args:
+                a: first for a reason
+                b: coming for `a`'s title
+            '''
+            return 0
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @r"
+        def my_func(
+            a,
+            b
+        ) -> Unknown
+        ---------------------------------------------
+        This is such a great func!!
+
+        Args:
+            a: first for a reason
+            b: coming for `a`'s title
+
+        ---------------------------------------------
+        ```python
+        def my_func(
+            a,
+            b
+        ) -> Unknown
+        ```
+        ---
+        ```text
+        This is such a great func!!
+
+        Args:
+            a: first for a reason
+            b: coming for `a`'s title
+
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:2:13
+          |
+        2 |         def my_func(a, b):
+          |             ^^^^^-^
+          |             |    |
+          |             |    Cursor offset
+          |             source
+        3 |             '''This is such a great func!!
+          |
+        ");
+    }
+
     #[test]
     fn hover_class() {
         let test = cursor_test(
@@ -304,6 +370,71 @@ mod tests {
         ");
     }
 
+    #[test]
+    fn hover_class_def() {
+        let test = cursor_test(
+            r#"
+        class MyCla<CURSOR>ss:
+            '''
+                This is such a great class!!
+
+                    Don't you know?
+                
+                Everyone loves my class!!
+
+            '''
+            def __init__(self, val):
+                """initializes MyClass (perfectly)"""
+                self.val = val
+            
+            def my_method(self, a, b):
+                '''This is such a great func!!
+
+                Args:
+                    a: first for a reason
+                    b: coming for `a`'s title
+                '''
+                return 0
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @r"
+        <class 'MyClass'>
+        ---------------------------------------------
+        This is such a great class!!
+
+            Don't you know?
+
+        Everyone loves my class!!
+
+        ---------------------------------------------
+        ```python
+        <class 'MyClass'>
+        ```
+        ---
+        ```text
+        This is such a great class!!
+
+            Don't you know?
+
+        Everyone loves my class!!
+
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:2:15
+          |
+        2 |         class MyClass:
+          |               ^^^^^-^
+          |               |    |
+          |               |    Cursor offset
+          |               source
+        3 |             '''
+        4 |                 This is such a great class!!
+          |
+        ");
+    }
+
     #[test]
     fn hover_class_init() {
         let test = cursor_test(
@@ -403,7 +534,10 @@ mod tests {
         );
 
         assert_snapshot!(test.hover(), @r"
-        bound method MyClass.my_method(a, b) -> Unknown
+        bound method MyClass.my_method(
+            a,
+            b
+        ) -> Unknown
         ---------------------------------------------
         This is such a great func!!
 
@@ -413,7 +547,10 @@ mod tests {
 
         ---------------------------------------------
         ```python
-        bound method MyClass.my_method(a, b) -> Unknown
+        bound method MyClass.my_method(
+            a,
+            b
+        ) -> Unknown
         ```
         ---
         ```text
@@ -485,10 +622,16 @@ mod tests {
         );
 
         assert_snapshot!(test.hover(), @r"
-        def foo(a, b) -> Unknown
+        def foo(
+            a,
+            b
+        ) -> Unknown
         ---------------------------------------------
         ```python
-        def foo(a, b) -> Unknown
+        def foo(
+            a,
+            b
+        ) -> Unknown
         ```
         ---------------------------------------------
         info[hover]: Hovered content is
@@ -571,6 +714,40 @@ mod tests {
         ");
     }
 
+    #[test]
+    fn hover_keyword_parameter_def() {
+        let test = cursor_test(
+            r#"
+            def test(a<CURSOR>b: int):
+                """my cool test
+
+                Args:
+                    ab: a nice little integer
+                """
+                return 0
+            "#,
+        );
+
+        assert_snapshot!(test.hover(), @r#"
+        int
+        ---------------------------------------------
+        ```python
+        int
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:2:22
+          |
+        2 |             def test(ab: int):
+          |                      ^-
+          |                      ||
+          |                      |Cursor offset
+          |                      source
+        3 |                 """my cool test
+          |
+        "#);
+    }
+
     #[test]
     fn hover_union() {
         let test = cursor_test(
@@ -613,6 +790,128 @@ mod tests {
         ");
     }
 
+    #[test]
+    fn hover_overload() {
+        let test = cursor_test(
+            r#"
+            from typing import overload
+
+            @overload
+            def foo(a: int, b):
+                """The first overload"""
+                return 0
+
+            @overload
+            def foo(a: str, b):
+                """The second overload"""
+                return 1
+
+            if random.choice([True, False]):
+                a = 1
+            else:
+                a = "hello"
+
+            foo<CURSOR>(a, 2)
+            "#,
+        );
+
+        assert_snapshot!(test.hover(), @r#"
+        (
+            a: int,
+            b
+        ) -> Unknown
+        (
+            a: str,
+            b
+        ) -> Unknown
+        ---------------------------------------------
+        The first overload
+
+        ---------------------------------------------
+        ```python
+        (
+            a: int,
+            b
+        ) -> Unknown
+        (
+            a: str,
+            b
+        ) -> Unknown
+        ```
+        ---
+        ```text
+        The first overload
+
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+          --> main.py:19:13
+           |
+        17 |                 a = "hello"
+        18 |
+        19 |             foo(a, 2)
+           |             ^^^- Cursor offset
+           |             |
+           |             source
+           |
+        "#);
+    }
+
+    #[test]
+    fn hover_overload_compact() {
+        let test = cursor_test(
+            r#"
+            from typing import overload
+
+            @overload
+            def foo(a: int):
+                """The first overload"""
+                return 0
+
+            @overload
+            def foo(a: str):
+                """The second overload"""
+                return 1
+
+            if random.choice([True, False]):
+                a = 1
+            else:
+                a = "hello"
+
+            foo<CURSOR>(a)
+            "#,
+        );
+
+        assert_snapshot!(test.hover(), @r#"
+        (a: int) -> Unknown
+        (a: str) -> Unknown
+        ---------------------------------------------
+        The first overload
+
+        ---------------------------------------------
+        ```python
+        (a: int) -> Unknown
+        (a: str) -> Unknown
+        ```
+        ---
+        ```text
+        The first overload
+
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+          --> main.py:19:13
+           |
+        17 |                 a = "hello"
+        18 |
+        19 |             foo(a)
+           |             ^^^- Cursor offset
+           |             |
+           |             source
+           |
+        "#);
+    }
+
     #[test]
     fn hover_module() {
         let mut test = cursor_test(
@@ -1081,6 +1380,110 @@ mod tests {
         assert_snapshot!(test.hover(), @"Hover provided no content");
     }
 
+    #[test]
+    fn hover_complex_type1() {
+        let test = cursor_test(
+            r#"
+        from typing import Callable, Any, List
+        def ab(x: int, y: Callable[[int, int], Any], z: List[int]) -> int: ...
+
+        a<CURSOR>b
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @r"
+        def ab(
+            x: int,
+            y: (int, int, /) -> Any,
+            z: list[int]
+        ) -> int
+        ---------------------------------------------
+        ```python
+        def ab(
+            x: int,
+            y: (int, int, /) -> Any,
+            z: list[int]
+        ) -> int
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:5:9
+          |
+        3 |         def ab(x: int, y: Callable[[int, int], Any], z: List[int]) -> int: ...
+        4 |
+        5 |         ab
+          |         ^-
+          |         ||
+          |         |Cursor offset
+          |         source
+          |
+        ");
+    }
+
+    #[test]
+    fn hover_complex_type2() {
+        let test = cursor_test(
+            r#"
+        from typing import Callable, Tuple, Any
+        ab: Tuple[Any, int, Callable[[int, int], Any]] = ...
+
+        a<CURSOR>b
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @r"
+        tuple[Any, int, (int, int, /) -> Any]
+        ---------------------------------------------
+        ```python
+        tuple[Any, int, (int, int, /) -> Any]
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:5:9
+          |
+        3 |         ab: Tuple[Any, int, Callable[[int, int], Any]] = ...
+        4 |
+        5 |         ab
+          |         ^-
+          |         ||
+          |         |Cursor offset
+          |         source
+          |
+        ");
+    }
+
+    #[test]
+    fn hover_complex_type3() {
+        let test = cursor_test(
+            r#"
+        from typing import Callable, Any
+        ab:  Callable[[int, int], Any] | None  = ...
+
+        a<CURSOR>b
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @r"
+        ((int, int, /) -> Any) | None
+        ---------------------------------------------
+        ```python
+        ((int, int, /) -> Any) | None
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:5:9
+          |
+        3 |         ab:  Callable[[int, int], Any] | None  = ...
+        4 |
+        5 |         ab
+          |         ^-
+          |         ||
+          |         |Cursor offset
+          |         source
+          |
+        ");
+    }
+
     #[test]
     fn hover_docstring() {
         let test = cursor_test(

crates/ty_ide/src/inlay_hints.rs

@@ -85,6 +85,13 @@ pub struct InlayHintSettings {
     /// foo("x="1)
     /// ```
     pub call_argument_names: bool,
+    // Add any new setting that enables additional inlays to `any_enabled`.
+}
+
+impl InlayHintSettings {
+    pub fn any_enabled(&self) -> bool {
+        self.variable_types || self.call_argument_names
+    }
 }
 
 impl Default for InlayHintSettings {

crates/ty_ide/src/lib.rs

@@ -235,7 +235,8 @@ impl HasNavigationTargets for Type<'_> {
     fn navigation_targets(&self, db: &dyn Db) -> NavigationTargets {
         match self {
             Type::Union(union) => union
-                .iter(db)
+                .elements(db)
+                .iter()
                 .flat_map(|target| target.navigation_targets(db))
                 .collect(),
 

crates/ty_ide/src/semantic_tokens.rs

@@ -337,7 +337,9 @@ impl<'db> SemanticTokenVisitor<'db> {
 
         match ty {
             Type::ClassLiteral(_) => (SemanticTokenType::Class, modifiers),
-            Type::TypeVar(_) => (SemanticTokenType::TypeParameter, modifiers),
+            Type::NonInferableTypeVar(_) | Type::TypeVar(_) => {
+                (SemanticTokenType::TypeParameter, modifiers)
+            }
             Type::FunctionLiteral(_) => {
                 // Check if this is a method based on current scope
                 if self.in_class_scope {

crates/ty_project/src/db.rs

@@ -21,6 +21,8 @@ mod changes;
 #[salsa::db]
 pub trait Db: SemanticDb {
     fn project(&self) -> Project;
+
+    fn dyn_clone(&self) -> Box<dyn Db>;
 }
 
 #[salsa::db]
@@ -484,6 +486,10 @@ impl Db for ProjectDatabase {
     fn project(&self) -> Project {
         self.project.unwrap()
     }
+
+    fn dyn_clone(&self) -> Box<dyn Db> {
+        Box::new(self.clone())
+    }
 }
 
 #[cfg(feature = "format")]
@@ -611,6 +617,10 @@ pub(crate) mod tests {
         fn project(&self) -> Project {
             self.project.unwrap()
         }
+
+        fn dyn_clone(&self) -> Box<dyn Db> {
+            Box::new(self.clone())
+        }
     }
 
     #[salsa::db]

crates/ty_project/src/metadata/options.rs

@@ -498,7 +498,7 @@ pub struct EnvironmentOptions {
         default = r#"[]"#,
         value_type = "list[str]",
         example = r#"
-            extra-paths = ["~/shared/my-search-path"]
+            extra-paths = ["./shared/my-search-path"]
         "#
     )]
     pub extra_paths: Option<Vec<RelativePathBuf>>,

crates/ty_project/src/walk.rs

@@ -4,7 +4,7 @@ use ruff_db::files::{File, system_path_to_file};
 use ruff_db::system::walk_directory::{ErrorKind, WalkDirectoryBuilder, WalkState};
 use ruff_db::system::{SystemPath, SystemPathBuf};
 use ruff_python_ast::PySourceType;
-use rustc_hash::{FxBuildHasher, FxHashSet};
+use rustc_hash::FxHashSet;
 use std::path::PathBuf;
 use thiserror::Error;
 
@@ -163,20 +163,24 @@ impl<'a> ProjectFilesWalker<'a> {
 
     /// Walks the project paths and collects the paths of all files that
     /// are included in the project.
-    pub(crate) fn walk_paths(self) -> (Vec<SystemPathBuf>, Vec<IOErrorDiagnostic>) {
-        let paths = std::sync::Mutex::new(Vec::new());
+    pub(crate) fn collect_vec(self, db: &dyn Db) -> (Vec<File>, Vec<IOErrorDiagnostic>) {
+        let files = std::sync::Mutex::new(Vec::new());
         let diagnostics = std::sync::Mutex::new(Vec::new());
 
         self.walker.run(|| {
-            Box::new(|entry| {
+            let db = db.dyn_clone();
+            let filter = &self.filter;
+            let files = &files;
+            let diagnostics = &diagnostics;
+
+            Box::new(move |entry| {
                 match entry {
                     Ok(entry) => {
                         // Skip excluded directories unless they were explicitly passed to the walker
                         // (which is the case passed to `ty check <paths>`).
                         if entry.file_type().is_directory() {
                             if entry.depth() > 0 {
-                                let directory_included = self
-                                    .filter
+                                let directory_included = filter
                                     .is_directory_included(entry.path(), GlobFilterCheckMode::TopDown);
                                 return match directory_included {
                                     IncludeResult::Included => WalkState::Continue,
@@ -210,8 +214,7 @@ impl<'a> ProjectFilesWalker<'a> {
                             // For all files, except the ones that were explicitly passed to the walker (CLI),
                             // check if they're included in the project.
                             if entry.depth() > 0 {
-                                match self
-                                    .filter
+                                match filter
                                     .is_file_included(entry.path(), GlobFilterCheckMode::TopDown)
                                 {
                                     IncludeResult::Included => {},
@@ -232,8 +235,11 @@ impl<'a> ProjectFilesWalker<'a> {
                                 }
                             }
 
-                            let mut paths = paths.lock().unwrap();
-                            paths.push(entry.into_path());
+                            // If this returns `Err`, then the file was deleted between now and when the walk callback was called.
+                            // We can ignore this.
+                            if let Ok(file) = system_path_to_file(&*db, entry.path()) {
+                                files.lock().unwrap().push(file);
+                            }
                         }
                     }
                     Err(error) => match error.kind() {
@@ -274,39 +280,14 @@ impl<'a> ProjectFilesWalker<'a> {
         });
 
         (
-            paths.into_inner().unwrap(),
+            files.into_inner().unwrap(),
             diagnostics.into_inner().unwrap(),
         )
     }
 
-    pub(crate) fn collect_vec(self, db: &dyn Db) -> (Vec<File>, Vec<IOErrorDiagnostic>) {
-        let (paths, diagnostics) = self.walk_paths();
-
-        (
-            paths
-                .into_iter()
-                .filter_map(move |path| {
-                    // If this returns `None`, then the file was deleted between the `walk_directory` call and now.
-                    // We can ignore this.
-                    system_path_to_file(db, &path).ok()
-                })
-                .collect(),
-            diagnostics,
-        )
-    }
-
     pub(crate) fn collect_set(self, db: &dyn Db) -> (FxHashSet<File>, Vec<IOErrorDiagnostic>) {
-        let (paths, diagnostics) = self.walk_paths();
-
-        let mut files = FxHashSet::with_capacity_and_hasher(paths.len(), FxBuildHasher);
-
-        for path in paths {
-            if let Ok(file) = system_path_to_file(db, &path) {
-                files.insert(file);
-            }
-        }
-
-        (files, diagnostics)
+        let (files, diagnostics) = self.collect_vec(db);
+        (files.into_iter().collect(), diagnostics)
     }
 }
 

crates/ty_python_semantic/resources/mdtest/annotations/self.md

@@ -1,16 +1,16 @@
 # Self
 
+```toml
+[environment]
+python-version = "3.11"
+```
+
 `Self` is treated as if it were a `TypeVar` bound to the class it's being used on.
 
 `typing.Self` is only available in Python 3.11 and later.
 
 ## Methods
 
-```toml
-[environment]
-python-version = "3.11"
-```
-
 ```py
 from typing import Self
 
@@ -74,11 +74,6 @@ reveal_type(C().method())  # revealed: C
 
 ## Class Methods
 
-```toml
-[environment]
-python-version = "3.11"
-```
-
 ```py
 from typing import Self, TypeVar
 
@@ -101,11 +96,6 @@ reveal_type(Shape.bar())  # revealed: Unknown
 
 ## Attributes
 
-```toml
-[environment]
-python-version = "3.11"
-```
-
 TODO: The use of `Self` to annotate the `next_node` attribute should be
 [modeled as a property][self attribute], using `Self` in its parameter and return type.
 
@@ -127,11 +117,6 @@ reveal_type(LinkedList().next())  # revealed: LinkedList
 
 ## Generic Classes
 
-```toml
-[environment]
-python-version = "3.11"
-```
-
 ```py
 from typing import Self, Generic, TypeVar
 
@@ -153,11 +138,6 @@ TODO: <https://typing.python.org/en/latest/spec/generics.html#use-in-protocols>
 
 ## Annotations
 
-```toml
-[environment]
-python-version = "3.11"
-```
-
 ```py
 from typing import Self
 
@@ -171,11 +151,6 @@ class Shape:
 
 `Self` cannot be used in the signature of a function or variable.
 
-```toml
-[environment]
-python-version = "3.11"
-```
-
 ```py
 from typing import Self, Generic, TypeVar
 
@@ -218,4 +193,33 @@ class MyMetaclass(type):
         return super().__new__(cls)
 ```
 
+## Binding a method fixes `Self`
+
+When a method is bound, any instances of `Self` in its signature are "fixed", since we now know the
+specific type of the bound parameter.
+
+```py
+from typing import Self
+
+class C:
+    def instance_method(self, other: Self) -> Self:
+        return self
+
+    @classmethod
+    def class_method(cls) -> Self:
+        return cls()
+
+# revealed: bound method C.instance_method(other: C) -> C
+reveal_type(C().instance_method)
+# revealed: bound method <class 'C'>.class_method() -> C
+reveal_type(C.class_method)
+
+class D(C): ...
+
+# revealed: bound method D.instance_method(other: D) -> D
+reveal_type(D().instance_method)
+# revealed: bound method <class 'D'>.class_method() -> D
+reveal_type(D.class_method)
+```
+
 [self attribute]: https://typing.python.org/en/latest/spec/generics.html#use-in-attribute-annotations

crates/ty_python_semantic/resources/mdtest/call/methods.md

@@ -198,7 +198,7 @@ python-version = "3.12"
 ```py
 type IntOrStr = int | str
 
-reveal_type(IntOrStr.__or__)  # revealed: bound method typing.TypeAliasType.__or__(right: Any) -> _SpecialForm
+reveal_type(IntOrStr.__or__)  # revealed: bound method typing.TypeAliasType.__or__(right: Any, /) -> _SpecialForm
 ```
 
 ## Method calls on types not disjoint from `None`

crates/ty_python_semantic/resources/mdtest/call/overloads.md

@@ -876,8 +876,7 @@ def _(list_int: list[int], list_str: list[str], list_any: list[Any], any: Any):
     # TODO: revealed: A
     reveal_type(f(*(list_int,)))  # revealed: Unknown
 
-    # TODO: Should be `str`
-    reveal_type(f(list_str))  # revealed: Unknown
+    reveal_type(f(list_str))  # revealed: str
     # TODO: Should be `str`
     reveal_type(f(*(list_str,)))  # revealed: Unknown
 

crates/ty_python_semantic/resources/mdtest/class/super.md

@@ -331,6 +331,9 @@ instance or a subclass of the first. If either condition is violated, a `TypeErr
 runtime.
 
 ```py
+import typing
+import collections
+
 def f(x: int):
     # error: [invalid-super-argument] "`int` is not a valid class"
     super(x, x)
@@ -367,6 +370,19 @@ reveal_type(super(B, A))
 reveal_type(super(B, object))
 
 super(object, object()).__class__
+
+# Not all objects valid in a class's bases list are valid as the first argument to `super()`.
+# For example, it's valid to inherit from `typing.ChainMap`, but it's not valid as the first argument to `super()`.
+#
+# error: [invalid-super-argument] "`typing.ChainMap` is not a valid class"
+reveal_type(super(typing.ChainMap, collections.ChainMap()))  # revealed: Unknown
+
+# Meanwhile, it's not valid to inherit from unsubscripted `typing.Generic`,
+# but it *is* valid as the first argument to `super()`.
+reveal_type(super(typing.Generic, typing.SupportsInt))  # revealed: <super: typing.Generic, <class 'SupportsInt'>>
+
+def _(x: type[typing.Any], y: typing.Any):
+    reveal_type(super(x, y))  # revealed: <super: Any, Any>
 ```
 
 ### Instance Member Access via `super`

crates/ty_python_semantic/resources/mdtest/dataclasses/dataclasses.md

@@ -988,6 +988,28 @@ class D:  # error: [duplicate-kw-only]
         z: float
 ```
 
+`KW_ONLY` should only affect fields declared after it within the same class, not fields in
+subclasses:
+
+```py
+from dataclasses import dataclass, KW_ONLY
+
+@dataclass
+class D:
+    x: int
+    _: KW_ONLY
+    y: str
+
+@dataclass
+class E(D):
+    z: bytes
+
+# This should work: x=1 (positional), z=b"foo" (positional), y="foo" (keyword-only)
+E(1, b"foo", y="foo")
+
+reveal_type(E.__init__)  # revealed: (self: E, x: int, z: bytes, *, y: str) -> None
+```
+
 ## Other special cases
 
 ### `dataclasses.dataclass`

crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_await.md

@@ -0,0 +1,105 @@
+# Invalid await diagnostics
+
+<!-- snapshot-diagnostics -->
+
+## Basic
+
+This is a test showcasing a primitive case where an object is not awaitable.
+
+```py
+async def main() -> None:
+    await 1  # error: [invalid-await]
+```
+
+## Custom type with missing `__await__`
+
+This diagnostic also points to the class definition if available.
+
+```py
+class MissingAwait:
+    pass
+
+async def main() -> None:
+    await MissingAwait()  # error: [invalid-await]
+```
+
+## Custom type with possibly unbound `__await__`
+
+This diagnostic also points to the method definition if available.
+
+```py
+from datetime import datetime
+
+class PossiblyUnbound:
+    if datetime.today().weekday() == 0:
+        def __await__(self):
+            yield
+
+async def main() -> None:
+    await PossiblyUnbound()  # error: [invalid-await]
+```
+
+## `__await__` definition with extra arguments
+
+Currently, the signature of `__await__` isn't checked for conformity with the `Awaitable` protocol
+directly. Instead, individual anomalies are reported, such as the following. Here, the diagnostic
+reports that the object is not implicitly awaitable, while also pointing at the function parameters.
+
+```py
+class InvalidAwaitArgs:
+    def __await__(self, value: int):
+        yield value
+
+async def main() -> None:
+    await InvalidAwaitArgs()  # error: [invalid-await]
+```
+
+## Non-callable `__await__`
+
+This diagnostic doesn't point to the attribute definition, but complains about it being possibly not
+awaitable.
+
+```py
+class NonCallableAwait:
+    __await__ = 42
+
+async def main() -> None:
+    await NonCallableAwait()  # error: [invalid-await]
+```
+
+## `__await__` definition with explicit invalid return type
+
+`__await__` must return a valid iterator. This diagnostic also points to the method definition if
+available.
+
+```py
+class InvalidAwaitReturn:
+    def __await__(self) -> int:
+        return 5
+
+async def main() -> None:
+    await InvalidAwaitReturn()  # error: [invalid-await]
+```
+
+## Invalid union return type
+
+When multiple potential definitions of `__await__` exist, all of them must be proper in order for an
+instance to be awaitable. In this specific case, no specific function definition is highlighted.
+
+```py
+import typing
+from datetime import datetime
+
+class UnawaitableUnion:
+    if datetime.today().weekday() == 6:
+
+        def __await__(self) -> typing.Generator[typing.Any, None, None]:
+            yield
+    else:
+
+        def __await__(self) -> int:
+            return 5
+
+async def main() -> None:
+    await UnawaitableUnion()  # error: [invalid-await]
+```

crates/ty_python_semantic/resources/mdtest/enums.md

@@ -749,6 +749,51 @@ def singleton_check(value: Singleton) -> str:
             assert_never(value)
 ```
 
+## `__eq__` and `__ne__`
+
+### No `__eq__` or `__ne__` overrides
+
+```py
+from enum import Enum
+
+class Color(Enum):
+    RED = 1
+    GREEN = 2
+
+reveal_type(Color.RED == Color.RED)  # revealed: Literal[True]
+reveal_type(Color.RED != Color.RED)  # revealed: Literal[False]
+```
+
+### Overridden `__eq__`
+
+```py
+from enum import Enum
+
+class Color(Enum):
+    RED = 1
+    GREEN = 2
+
+    def __eq__(self, other: object) -> bool:
+        return False
+
+reveal_type(Color.RED == Color.RED)  # revealed: bool
+```
+
+### Overridden `__ne__`
+
+```py
+from enum import Enum
+
+class Color(Enum):
+    RED = 1
+    GREEN = 2
+
+    def __ne__(self, other: object) -> bool:
+        return False
+
+reveal_type(Color.RED != Color.RED)  # revealed: bool
+```
+
 ## References
 
 - Typing spec: <https://typing.python.org/en/latest/spec/enums.html>

crates/ty_python_semantic/resources/mdtest/generics/legacy/classes.md

@@ -491,6 +491,24 @@ class A(Generic[T]):
 reveal_type(A(x=1))  # revealed: A[int]
 ```
 
+### Class typevar has another typevar as a default
+
+```py
+from typing import Generic, TypeVar
+
+T = TypeVar("T")
+U = TypeVar("U", default=T)
+
+class C(Generic[T, U]): ...
+
+reveal_type(C())  # revealed: C[Unknown, Unknown]
+
+class D(Generic[T, U]):
+    def __init__(self) -> None: ...
+
+reveal_type(D())  # revealed: D[Unknown, Unknown]
+```
+
 ## Generic subclass
 
 When a generic subclass fills its superclass's type parameter with one of its own, the actual types

crates/ty_python_semantic/resources/mdtest/generics/legacy/functions.md

@@ -455,3 +455,45 @@ def overloaded_outer(t: T | None = None) -> None:
     if t is not None:
         inner(t)
 ```
+
+## Unpacking a TypeVar
+
+We can infer precise heterogeneous types from the result of an unpacking operation applied to a type
+variable if the type variable's upper bound is a type with a precise tuple spec:
+
+```py
+from dataclasses import dataclass
+from typing import NamedTuple, Final, TypeVar, Generic
+
+T = TypeVar("T", bound=tuple[int, str])
+
+def f(x: T) -> T:
+    a, b = x
+    reveal_type(a)  # revealed: int
+    reveal_type(b)  # revealed: str
+    return x
+
+@dataclass
+class Team(Generic[T]):
+    employees: list[T]
+
+def x(team: Team[T]) -> Team[T]:
+    age, name = team.employees[0]
+    reveal_type(age)  # revealed: int
+    reveal_type(name)  # revealed: str
+    return team
+
+class Age(int): ...
+class Name(str): ...
+
+class Employee(NamedTuple):
+    age: Age
+    name: Name
+
+EMPLOYEES: Final = (Employee(name=Name("alice"), age=Age(42)),)
+team = Team(employees=list(EMPLOYEES))
+reveal_type(team.employees)  # revealed: list[Employee]
+age, name = team.employees[0]
+reveal_type(age)  # revealed: Age
+reveal_type(name)  # revealed: Name
+```

crates/ty_python_semantic/resources/mdtest/generics/pep695/classes.md

@@ -237,10 +237,15 @@ If the type of a constructor parameter is a class typevar, we can use that to in
 parameter. The types inferred from a type context and from a constructor parameter must be
 consistent with each other.
 
+We have to add `x: T` to the classes to ensure they're not bivariant in `T` (__new__ and __init__
+signatures don't count towards variance).
+
 ### `__new__` only
 
 ```py
 class C[T]:
+    x: T
+
     def __new__(cls, x: T) -> "C[T]":
         return object.__new__(cls)
 
@@ -254,6 +259,8 @@ wrong_innards: C[int] = C("five")
 
 ```py
 class C[T]:
+    x: T
+
     def __init__(self, x: T) -> None: ...
 
 reveal_type(C(1))  # revealed: C[int]
@@ -266,6 +273,8 @@ wrong_innards: C[int] = C("five")
 
 ```py
 class C[T]:
+    x: T
+
     def __new__(cls, x: T) -> "C[T]":
         return object.__new__(cls)
 
@@ -281,6 +290,8 @@ wrong_innards: C[int] = C("five")
 
 ```py
 class C[T]:
+    x: T
+
     def __new__(cls, *args, **kwargs) -> "C[T]":
         return object.__new__(cls)
 
@@ -292,6 +303,8 @@ reveal_type(C(1))  # revealed: C[int]
 wrong_innards: C[int] = C("five")
 
 class D[T]:
+    x: T
+
     def __new__(cls, x: T) -> "D[T]":
         return object.__new__(cls)
 
@@ -378,6 +391,8 @@ def func8(t1: tuple[complex, list[int]], t2: tuple[int, *tuple[str, ...]], t3: t
 
 ```py
 class C[T]:
+    x: T
+
     def __init__[S](self, x: T, y: S) -> None: ...
 
 reveal_type(C(1, 1))  # revealed: C[int]
@@ -395,6 +410,10 @@ from __future__ import annotations
 from typing import overload
 
 class C[T]:
+    # we need to use the type variable or else the class is bivariant in T, and
+    # specializations become meaningless
+    x: T
+
     @overload
     def __init__(self: C[str], x: str) -> None: ...
     @overload
@@ -438,6 +457,19 @@ class A[T]:
 reveal_type(A(x=1))  # revealed: A[int]
 ```
 
+### Class typevar has another typevar as a default
+
+```py
+class C[T, U = T]: ...
+
+reveal_type(C())  # revealed: C[Unknown, Unknown]
+
+class D[T, U = T]:
+    def __init__(self) -> None: ...
+
+reveal_type(D())  # revealed: D[Unknown, Unknown]
+```
+
 ## Generic subclass
 
 When a generic subclass fills its superclass's type parameter with one of its own, the actual types
@@ -617,5 +649,34 @@ class C[T](C): ...
 class D[T](D[int]): ...
 ```
 
+## Tuple as a PEP-695 generic class
+
+Our special handling for `tuple` does not break if `tuple` is defined as a PEP-695 generic class in
+typeshed:
+
+```toml
+[environment]
+python-version = "3.12"
+typeshed = "/typeshed"
+```
+
+`/typeshed/stdlib/builtins.pyi`:
+
+```pyi
+class tuple[T]: ...
+```
+
+`/typeshed/stdlib/typing_extensions.pyi`:
+
+```pyi
+def reveal_type(obj, /): ...
+```
+
+`main.py`:
+
+```py
+reveal_type((1, 2, 3))  # revealed: tuple[Literal[1], Literal[2], Literal[3]]
+```
+
 [crtp]: https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern
 [f-bound]: https://en.wikipedia.org/wiki/Bounded_quantification#F-bounded_quantification

crates/ty_python_semantic/resources/mdtest/generics/pep695/functions.md

@@ -454,3 +454,43 @@ def overloaded_outer[T](t: T | None = None) -> None:
     if t is not None:
         inner(t)
 ```
+
+## Unpacking a TypeVar
+
+We can infer precise heterogeneous types from the result of an unpacking operation applied to a
+TypeVar if the TypeVar's upper bound is a type with a precise tuple spec:
+
+```py
+from dataclasses import dataclass
+from typing import NamedTuple, Final
+
+def f[T: tuple[int, str]](x: T) -> T:
+    a, b = x
+    reveal_type(a)  # revealed: int
+    reveal_type(b)  # revealed: str
+    return x
+
+@dataclass
+class Team[T: tuple[int, str]]:
+    employees: list[T]
+
+def x[T: tuple[int, str]](team: Team[T]) -> Team[T]:
+    age, name = team.employees[0]
+    reveal_type(age)  # revealed: int
+    reveal_type(name)  # revealed: str
+    return team
+
+class Age(int): ...
+class Name(str): ...
+
+class Employee(NamedTuple):
+    age: Age
+    name: Name
+
+EMPLOYEES: Final = (Employee(name=Name("alice"), age=Age(42)),)
+team = Team(employees=list(EMPLOYEES))
+reveal_type(team.employees)  # revealed: list[Employee]
+age, name = team.employees[0]
+reveal_type(age)  # revealed: Age
+reveal_type(name)  # revealed: Name
+```

crates/ty_python_semantic/resources/mdtest/generics/pep695/variance.md

@@ -40,8 +40,6 @@ class C[T]:
 class D[U](C[U]):
     pass
 
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_assignable_to(C[B], C[A]))
 static_assert(not is_assignable_to(C[A], C[B]))
 static_assert(is_assignable_to(C[A], C[Any]))
@@ -49,8 +47,6 @@ static_assert(is_assignable_to(C[B], C[Any]))
 static_assert(is_assignable_to(C[Any], C[A]))
 static_assert(is_assignable_to(C[Any], C[B]))
 
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_assignable_to(D[B], C[A]))
 static_assert(not is_assignable_to(D[A], C[B]))
 static_assert(is_assignable_to(D[A], C[Any]))
@@ -58,8 +54,6 @@ static_assert(is_assignable_to(D[B], C[Any]))
 static_assert(is_assignable_to(D[Any], C[A]))
 static_assert(is_assignable_to(D[Any], C[B]))
 
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_subtype_of(C[B], C[A]))
 static_assert(not is_subtype_of(C[A], C[B]))
 static_assert(not is_subtype_of(C[A], C[Any]))
@@ -67,8 +61,6 @@ static_assert(not is_subtype_of(C[B], C[Any]))
 static_assert(not is_subtype_of(C[Any], C[A]))
 static_assert(not is_subtype_of(C[Any], C[B]))
 
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_subtype_of(D[B], C[A]))
 static_assert(not is_subtype_of(D[A], C[B]))
 static_assert(not is_subtype_of(D[A], C[Any]))
@@ -124,8 +116,6 @@ class D[U](C[U]):
     pass
 
 static_assert(not is_assignable_to(C[B], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_assignable_to(C[A], C[B]))
 static_assert(is_assignable_to(C[A], C[Any]))
 static_assert(is_assignable_to(C[B], C[Any]))
@@ -133,8 +123,6 @@ static_assert(is_assignable_to(C[Any], C[A]))
 static_assert(is_assignable_to(C[Any], C[B]))
 
 static_assert(not is_assignable_to(D[B], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_assignable_to(D[A], C[B]))
 static_assert(is_assignable_to(D[A], C[Any]))
 static_assert(is_assignable_to(D[B], C[Any]))
@@ -142,8 +130,6 @@ static_assert(is_assignable_to(D[Any], C[A]))
 static_assert(is_assignable_to(D[Any], C[B]))
 
 static_assert(not is_subtype_of(C[B], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_subtype_of(C[A], C[B]))
 static_assert(not is_subtype_of(C[A], C[Any]))
 static_assert(not is_subtype_of(C[B], C[Any]))
@@ -151,8 +137,6 @@ static_assert(not is_subtype_of(C[Any], C[A]))
 static_assert(not is_subtype_of(C[Any], C[B]))
 
 static_assert(not is_subtype_of(D[B], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_subtype_of(D[A], C[B]))
 static_assert(not is_subtype_of(D[A], C[Any]))
 static_assert(not is_subtype_of(D[B], C[Any]))
@@ -297,34 +281,22 @@ class C[T]:
 class D[U](C[U]):
     pass
 
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_assignable_to(C[B], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_assignable_to(C[A], C[B]))
 static_assert(is_assignable_to(C[A], C[Any]))
 static_assert(is_assignable_to(C[B], C[Any]))
 static_assert(is_assignable_to(C[Any], C[A]))
 static_assert(is_assignable_to(C[Any], C[B]))
 
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_assignable_to(D[B], C[A]))
 static_assert(is_subtype_of(C[A], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_assignable_to(D[A], C[B]))
 static_assert(is_assignable_to(D[A], C[Any]))
 static_assert(is_assignable_to(D[B], C[Any]))
 static_assert(is_assignable_to(D[Any], C[A]))
 static_assert(is_assignable_to(D[Any], C[B]))
 
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_subtype_of(C[B], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_subtype_of(C[A], C[B]))
 static_assert(not is_subtype_of(C[A], C[Any]))
 static_assert(not is_subtype_of(C[B], C[Any]))
@@ -332,11 +304,7 @@ static_assert(not is_subtype_of(C[Any], C[A]))
 static_assert(not is_subtype_of(C[Any], C[B]))
 static_assert(not is_subtype_of(C[Any], C[Any]))
 
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_subtype_of(D[B], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_subtype_of(D[A], C[B]))
 static_assert(not is_subtype_of(D[A], C[Any]))
 static_assert(not is_subtype_of(D[B], C[Any]))
@@ -345,23 +313,11 @@ static_assert(not is_subtype_of(D[Any], C[B]))
 
 static_assert(is_equivalent_to(C[A], C[A]))
 static_assert(is_equivalent_to(C[B], C[B]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_equivalent_to(C[B], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_equivalent_to(C[A], C[B]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_equivalent_to(C[A], C[Any]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_equivalent_to(C[B], C[Any]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_equivalent_to(C[Any], C[A]))
-# TODO: no error
-# error: [static-assert-error]
 static_assert(is_equivalent_to(C[Any], C[B]))
 
 static_assert(not is_equivalent_to(D[A], C[A]))
@@ -380,4 +336,504 @@ static_assert(not is_equivalent_to(D[Any], C[Any]))
 static_assert(not is_equivalent_to(D[Any], C[Unknown]))
 ```
 
+## Mutual Recursion
+
+This example due to Martin Huschenbett's PyCon 2025 talk,
+[Linear Time variance Inference for PEP 695][linear-time-variance-talk]
+
+```py
+from ty_extensions import is_subtype_of, static_assert
+from typing import Any
+
+class A: ...
+class B(A): ...
+
+class C[X]:
+    def f(self) -> "D[X]":
+        return D()
+
+    def g(self, x: X) -> None: ...
+
+class D[Y]:
+    def h(self) -> C[Y]:
+        return C()
+```
+
+`C` is contravariant in `X`, and `D` in `Y`:
+
+- `C` has two occurrences of `X`
+    - `X` occurs in the return type of `f` as `D[X]` (`X` is substituted in for `Y`)
+        - `D` has one occurrence of `Y`
+            - `Y` occurs in the return type of `h` as `C[Y]`
+    - `X` occurs contravariantly as a parameter in `g`
+
+Thus the variance of `X` in `C` depends on itself. We want to infer the least restrictive possible
+variance, so in such cases we begin by assuming that the point where we detect the cycle is
+bivariant.
+
+If we thus assume `X` is bivariant in `C`, then `Y` will be bivariant in `D`, as `D`'s only
+occurrence of `Y` is in `C`. Then we consider `X` in `C` once more. We have two occurrences: `D[X]`
+covariantly in a return type, and `X` contravariantly in an argument type. With one bivariant and
+one contravariant occurrence, we update our inference of `X` in `C` to contravariant---the supremum
+of contravariant and bivariant in the lattice.
+
+Now that we've updated the variance of `X` in `C`, we re-evaluate `Y` in `D`. It only has the one
+occurrence `C[Y]`, which we now infer is contravariant, and so we infer contravariance for `Y` in
+`D` as well.
+
+Because the variance of `X` in `C` depends on that of `Y` in `D`, we have to re-evaluate now that
+we've updated the latter to contravariant. The variance of `X` in `C` is now the supremum of
+contravariant and contravariant---giving us contravariant---and so remains unchanged.
+
+Once we've completed a turn around the cycle with nothing changed, we've reached a fixed-point---the
+variance inference will not change any further---and so we finally conclude that both `X` in `C` and
+`Y` in `D` are contravariant.
+
+```py
+static_assert(not is_subtype_of(C[B], C[A]))
+static_assert(is_subtype_of(C[A], C[B]))
+static_assert(not is_subtype_of(C[A], C[Any]))
+static_assert(not is_subtype_of(C[B], C[Any]))
+static_assert(not is_subtype_of(C[Any], C[A]))
+static_assert(not is_subtype_of(C[Any], C[B]))
+
+static_assert(not is_subtype_of(D[B], D[A]))
+static_assert(is_subtype_of(D[A], D[B]))
+static_assert(not is_subtype_of(D[A], D[Any]))
+static_assert(not is_subtype_of(D[B], D[Any]))
+static_assert(not is_subtype_of(D[Any], D[A]))
+static_assert(not is_subtype_of(D[Any], D[B]))
+```
+
+## Class Attributes
+
+### Mutable Attributes
+
+Normal attributes are mutable, and so make the enclosing class invariant in this typevar (see
+[inv]).
+
+```py
+from ty_extensions import is_subtype_of, static_assert
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    x: T
+
+static_assert(not is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+```
+
+One might think that occurrences in the types of normal attributes are covariant, but they are
+mutable, and thus the occurrences are invariant.
+
+### Immutable Attributes
+
+Immutable attributes can't be written to, and thus constrain the typevar to covariance, not
+invariance.
+
+#### Final attributes
+
+```py
+from typing import Final
+from ty_extensions import is_subtype_of, static_assert
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    x: Final[T]
+
+static_assert(is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+```
+
+#### Underscore-prefixed attributes
+
+Underscore-prefixed instance attributes are considered private, and thus are assumed not externally
+mutated.
+
+```py
+from ty_extensions import is_subtype_of, static_assert
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    _x: T
+
+    @property
+    def x(self) -> T:
+        return self._x
+
+static_assert(is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+
+class D[T]:
+    def __init__(self, x: T):
+        self._x = x
+
+    @property
+    def x(self) -> T:
+        return self._x
+
+static_assert(is_subtype_of(D[B], D[A]))
+static_assert(not is_subtype_of(D[A], D[B]))
+```
+
+#### Frozen dataclasses in Python 3.12 and earlier
+
+```py
+from dataclasses import dataclass, field
+from ty_extensions import is_subtype_of, static_assert
+
+class A: ...
+class B(A): ...
+
+@dataclass(frozen=True)
+class D[U]:
+    y: U
+
+static_assert(is_subtype_of(D[B], D[A]))
+static_assert(not is_subtype_of(D[A], D[B]))
+
+@dataclass(frozen=True)
+class E[U]:
+    y: U = field()
+
+static_assert(is_subtype_of(E[B], E[A]))
+static_assert(not is_subtype_of(E[A], E[B]))
+```
+
+#### Frozen dataclasses in Python 3.13 and later
+
+```toml
+[environment]
+python-version = "3.13"
+```
+
+Python 3.13 introduced a new synthesized `__replace__` method on dataclasses, which uses every field
+type in a contravariant position (as a parameter to `__replace__`). This means that frozen
+dataclasses on Python 3.13+ can't be covariant in their field types.
+
+```py
+from dataclasses import dataclass
+from ty_extensions import is_subtype_of, static_assert
+
+class A: ...
+class B(A): ...
+
+@dataclass(frozen=True)
+class D[U]:
+    y: U
+
+static_assert(not is_subtype_of(D[B], D[A]))
+static_assert(not is_subtype_of(D[A], D[B]))
+```
+
+#### NamedTuple
+
+```py
+from typing import NamedTuple
+from ty_extensions import is_subtype_of, static_assert
+
+class A: ...
+class B(A): ...
+
+class E[V](NamedTuple):
+    z: V
+
+static_assert(is_subtype_of(E[B], E[A]))
+static_assert(not is_subtype_of(E[A], E[B]))
+```
+
+A subclass of a `NamedTuple` can still be covariant:
+
+```py
+class D[T](E[T]):
+    pass
+
+static_assert(is_subtype_of(D[B], D[A]))
+static_assert(not is_subtype_of(D[A], D[B]))
+```
+
+But adding a new generic attribute on the subclass makes it invariant (the added attribute is not a
+`NamedTuple` field, and thus not immutable):
+
+```py
+class C[T](E[T]):
+    w: T
+
+static_assert(not is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+```
+
+### Properties
+
+Properties constrain to covariance if they are get-only and invariant if they are get-set:
+
+```py
+from ty_extensions import static_assert, is_subtype_of
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    @property
+    def x(self) -> T | None:
+        return None
+
+class D[U]:
+    @property
+    def y(self) -> U | None:
+        return None
+
+    @y.setter
+    def y(self, value: U): ...
+
+static_assert(is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+static_assert(not is_subtype_of(D[B], D[A]))
+static_assert(not is_subtype_of(D[A], D[B]))
+```
+
+### Implicit Attributes
+
+Implicit attributes work like normal ones
+
+```py
+from ty_extensions import static_assert, is_subtype_of
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    def f(self) -> None:
+        self.x: T | None = None
+
+static_assert(not is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+```
+
+### Constructors: excluding `__init__` and `__new__`
+
+We consider it invalid to call `__init__` explicitly on an existing object. Likewise, `__new__` is
+only used at the beginning of an object's life. As such, we don't need to worry about the variance
+impact of these methods.
+
+```py
+from ty_extensions import static_assert, is_subtype_of
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    def __init__(self, x: T): ...
+    def __new__(self, x: T): ...
+
+static_assert(is_subtype_of(C[B], C[A]))
+static_assert(is_subtype_of(C[A], C[B]))
+```
+
+This example is then bivariant because it doesn't use `T` outside of the two exempted methods.
+
+This holds likewise for dataclasses with synthesized `__init__`:
+
+```py
+from dataclasses import dataclass
+
+@dataclass(init=True, frozen=True)
+class D[T]:
+    x: T
+
+# Covariant due to the read-only T-typed attribute; the `__init__` is ignored and doesn't make it
+# invariant:
+
+static_assert(is_subtype_of(D[B], D[A]))
+static_assert(not is_subtype_of(D[A], D[B]))
+```
+
+## Union Types
+
+Union types are covariant in all their members. If `A <: B`, then `A | C <: B | C` and
+`C | A <: C | B`.
+
+```py
+from ty_extensions import is_assignable_to, is_subtype_of, static_assert
+
+class A: ...
+class B(A): ...
+class C: ...
+
+# Union types are covariant in their members
+static_assert(is_subtype_of(B | C, A | C))
+static_assert(is_subtype_of(C | B, C | A))
+static_assert(not is_subtype_of(A | C, B | C))
+static_assert(not is_subtype_of(C | A, C | B))
+
+# Assignability follows the same pattern
+static_assert(is_assignable_to(B | C, A | C))
+static_assert(is_assignable_to(C | B, C | A))
+static_assert(not is_assignable_to(A | C, B | C))
+static_assert(not is_assignable_to(C | A, C | B))
+```
+
+## Intersection Types
+
+Intersection types cannot be expressed directly in Python syntax, but they occur when type narrowing
+creates constraints through control flow. In ty's representation, intersection types are covariant
+in their positive conjuncts and contravariant in their negative conjuncts.
+
+```py
+from ty_extensions import is_assignable_to, is_subtype_of, static_assert, Intersection, Not
+
+class A: ...
+class B(A): ...
+class C: ...
+
+# Test covariance in positive conjuncts
+# If B <: A, then Intersection[X, B] <: Intersection[X, A]
+static_assert(is_subtype_of(Intersection[C, B], Intersection[C, A]))
+static_assert(not is_subtype_of(Intersection[C, A], Intersection[C, B]))
+
+static_assert(is_assignable_to(Intersection[C, B], Intersection[C, A]))
+static_assert(not is_assignable_to(Intersection[C, A], Intersection[C, B]))
+
+# Test contravariance in negative conjuncts
+# If B <: A, then Intersection[X, Not[A]] <: Intersection[X, Not[B]]
+# (excluding supertype A is more restrictive than excluding subtype B)
+static_assert(is_subtype_of(Intersection[C, Not[A]], Intersection[C, Not[B]]))
+static_assert(not is_subtype_of(Intersection[C, Not[B]], Intersection[C, Not[A]]))
+
+static_assert(is_assignable_to(Intersection[C, Not[A]], Intersection[C, Not[B]]))
+static_assert(not is_assignable_to(Intersection[C, Not[B]], Intersection[C, Not[A]]))
+```
+
+## Subclass Types (type[T])
+
+The `type[T]` construct represents the type of classes that are subclasses of `T`. It is covariant
+in `T` because if `A <: B`, then `type[A] <: type[B]` holds.
+
+```py
+from ty_extensions import is_assignable_to, is_subtype_of, static_assert
+
+class A: ...
+class B(A): ...
+
+# type[T] is covariant in T
+static_assert(is_subtype_of(type[B], type[A]))
+static_assert(not is_subtype_of(type[A], type[B]))
+
+static_assert(is_assignable_to(type[B], type[A]))
+static_assert(not is_assignable_to(type[A], type[B]))
+
+# With generic classes using type[T]
+class ClassContainer[T]:
+    def __init__(self, cls: type[T]) -> None:
+        self.cls = cls
+
+    def create_instance(self) -> T:
+        return self.cls()
+
+# ClassContainer is covariant in T due to type[T]
+static_assert(is_subtype_of(ClassContainer[B], ClassContainer[A]))
+static_assert(not is_subtype_of(ClassContainer[A], ClassContainer[B]))
+
+static_assert(is_assignable_to(ClassContainer[B], ClassContainer[A]))
+static_assert(not is_assignable_to(ClassContainer[A], ClassContainer[B]))
+
+# Practical example: you can pass a ClassContainer[B] where ClassContainer[A] is expected
+# because type[B] can safely be used where type[A] is expected
+def use_a_class_container(container: ClassContainer[A]) -> A:
+    return container.create_instance()
+
+b_container = ClassContainer[B](B)
+a_instance: A = use_a_class_container(b_container)  # This should work
+```
+
+## Inheriting from generic classes with inferred variance
+
+When inheriting from a generic class with our type variable substituted in, we count its occurrences
+as well. In the following example, `T` is covariant in `C`, and contravariant in the subclass `D` if
+you only count its own occurrences. Because we count both then, `T` is invariant in `D`.
+
+```py
+from ty_extensions import is_subtype_of, static_assert
+
+class A:
+    pass
+
+class B(A):
+    pass
+
+class C[T]:
+    def f() -> T | None:
+        pass
+
+static_assert(is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+
+class D[T](C[T]):
+    def g(x: T) -> None:
+        pass
+
+static_assert(not is_subtype_of(D[B], D[A]))
+static_assert(not is_subtype_of(D[A], D[B]))
+```
+
+## Inheriting from generic classes with explicit variance
+
+```py
+from typing import TypeVar, Generic
+from ty_extensions import is_subtype_of, static_assert
+
+T = TypeVar("T")
+T_co = TypeVar("T_co", covariant=True)
+T_contra = TypeVar("T_contra", contravariant=True)
+
+class A:
+    pass
+
+class B(A):
+    pass
+
+class Invariant(Generic[T]):
+    pass
+
+static_assert(not is_subtype_of(Invariant[B], Invariant[A]))
+static_assert(not is_subtype_of(Invariant[A], Invariant[B]))
+
+class DerivedInvariant[T](Invariant[T]):
+    pass
+
+static_assert(not is_subtype_of(DerivedInvariant[B], DerivedInvariant[A]))
+static_assert(not is_subtype_of(DerivedInvariant[A], DerivedInvariant[B]))
+
+class Covariant(Generic[T_co]):
+    pass
+
+static_assert(is_subtype_of(Covariant[B], Covariant[A]))
+static_assert(not is_subtype_of(Covariant[A], Covariant[B]))
+
+class DerivedCovariant[T](Covariant[T]):
+    pass
+
+static_assert(is_subtype_of(DerivedCovariant[B], DerivedCovariant[A]))
+static_assert(not is_subtype_of(DerivedCovariant[A], DerivedCovariant[B]))
+
+class Contravariant(Generic[T_contra]):
+    pass
+
+static_assert(not is_subtype_of(Contravariant[B], Contravariant[A]))
+static_assert(is_subtype_of(Contravariant[A], Contravariant[B]))
+
+class DerivedContravariant[T](Contravariant[T]):
+    pass
+
+static_assert(not is_subtype_of(DerivedContravariant[B], DerivedContravariant[A]))
+static_assert(is_subtype_of(DerivedContravariant[A], DerivedContravariant[B]))
+```
+
+[linear-time-variance-talk]: https://www.youtube.com/watch?v=7uixlNTOY4s&t=9705s
 [spec]: https://typing.python.org/en/latest/spec/generics.html#variance

crates/ty_python_semantic/resources/mdtest/import/partial_stub_packages.md

@@ -0,0 +1,470 @@
+# Partial stub packages
+
+Partial stub packages are stubs that are allowed to be missing modules. See the
+[specification](https://peps.python.org/pep-0561/#partial-stub-packages). Partial stubs are also
+called "incomplete" packages, and non-partial stubs are called "complete" packages.
+
+Normally a stub package is expected to define a copy of every module the real implementation
+defines. Module resolution is consequently required to report a module doesn't exist if it finds
+`mypackage-stubs` and fails to find `mypackage.mymodule` *even if* `mypackage` does define
+`mymodule`.
+
+If a stub package declares that it's partial, we instead are expected to fall through to the
+implementation package and try to discover `mymodule` there. This is described as follows:
+
+> Type checkers should merge the stub package and runtime package or typeshed directories. This can
+> be thought of as the functional equivalent of copying the stub package into the same directory as
+> the corresponding runtime package or typeshed folder and type checking the combined directory
+> structure. Thus type checkers MUST maintain the normal resolution order of checking `*.pyi` before
+> `*.py` files.
+
+Namespace stub packages are always considered partial by necessity. Regular stub packages are only
+considered partial if they define a `py.typed` file containing the string `partial\n` (due to real
+stubs in the wild, we relax this and look case-insensitively for `partial`).
+
+The `py.typed` file was originally specified as an empty marker for "this package supports types",
+as a way to opt into having typecheckers run on a package. However ty and pyright choose to largely
+ignore this and just type check every package.
+
+In its original specification it was specified that subpackages inherit any `py.typed` declared in a
+parent package. However the precise interaction with `partial\n` was never specified. We currently
+implement a simple inheritance scheme where a subpackage can always declare its own `py.typed` and
+override whether it's partial or not.
+
+## Partial stub with missing module
+
+A stub package that includes a partial `py.typed` file.
+
+Here "both" is found in the stub, while "impl" is found in the implementation. "fake" is found in
+neither.
+
+```toml
+[environment]
+extra-paths = ["/packages"]
+```
+
+`/packages/foo-stubs/py.typed`:
+
+```text
+partial
+```
+
+`/packages/foo-stubs/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/both.pyi`:
+
+```pyi
+class Both:
+    both: str
+    other: int
+```
+
+`/packages/foo/__init__.py`:
+
+```py
+```
+
+`/packages/foo/both.py`:
+
+```py
+class Both: ...
+```
+
+`/packages/foo/impl.py`:
+
+```py
+class Impl:
+    impl: str
+    other: int
+```
+
+`main.py`:
+
+```py
+from foo.both import Both
+from foo.impl import Impl
+from foo.fake import Fake  # error: "Cannot resolve"
+
+reveal_type(Both().both)  # revealed: str
+reveal_type(Impl().impl)  # revealed: str
+reveal_type(Fake().fake)  # revealed: Unknown
+```
+
+## Non-partial stub with missing module
+
+Omitting the partial `py.typed`, we see "impl" now cannot be found.
+
+```toml
+[environment]
+extra-paths = ["/packages"]
+```
+
+`/packages/foo-stubs/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/both.pyi`:
+
+```pyi
+class Both:
+    both: str
+    other: int
+```
+
+`/packages/foo/__init__.py`:
+
+```py
+```
+
+`/packages/foo/both.py`:
+
+```py
+class Both: ...
+```
+
+`/packages/foo/impl.py`:
+
+```py
+class Impl:
+    impl: str
+    other: int
+```
+
+`main.py`:
+
+```py
+from foo.both import Both
+from foo.impl import Impl  # error: "Cannot resolve"
+from foo.fake import Fake  # error: "Cannot resolve"
+
+reveal_type(Both().both)  # revealed: str
+reveal_type(Impl().impl)  # revealed: Unknown
+reveal_type(Fake().fake)  # revealed: Unknown
+```
+
+## Full-typed stub with missing module
+
+Including a blank py.typed we still don't conclude it's partial.
+
+```toml
+[environment]
+extra-paths = ["/packages"]
+```
+
+`/packages/foo-stubs/py.typed`:
+
+```text
+```
+
+`/packages/foo-stubs/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/both.pyi`:
+
+```pyi
+class Both:
+    both: str
+    other: int
+```
+
+`/packages/foo/__init__.py`:
+
+```py
+```
+
+`/packages/foo/both.py`:
+
+```py
+class Both: ...
+```
+
+`/packages/foo/impl.py`:
+
+```py
+class Impl:
+    impl: str
+    other: int
+```
+
+`main.py`:
+
+```py
+from foo.both import Both
+from foo.impl import Impl  # error: "Cannot resolve"
+from foo.fake import Fake  # error: "Cannot resolve"
+
+reveal_type(Both().both)  # revealed: str
+reveal_type(Impl().impl)  # revealed: Unknown
+reveal_type(Fake().fake)  # revealed: Unknown
+```
+
+## Inheriting a partial `py.typed`
+
+`foo-stubs` defines a partial py.typed which is used by `foo-stubs/bar`
+
+```toml
+[environment]
+extra-paths = ["/packages"]
+```
+
+`/packages/foo-stubs/py.typed`:
+
+```text
+# Also testing permissive parsing
+# PARTIAL\n
+```
+
+`/packages/foo-stubs/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/bar/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/bar/both.pyi`:
+
+```pyi
+class Both:
+    both: str
+    other: int
+```
+
+`/packages/foo/__init__.py`:
+
+```py
+```
+
+`/packages/foo/bar/__init__.py`:
+
+```py
+```
+
+`/packages/foo/bar/both.py`:
+
+```py
+class Both: ...
+```
+
+`/packages/foo/bar/impl.py`:
+
+```py
+class Impl:
+    impl: str
+    other: int
+```
+
+`main.py`:
+
+```py
+from foo.bar.both import Both
+from foo.bar.impl import Impl
+from foo.bar.fake import Fake  # error: "Cannot resolve"
+
+reveal_type(Both().both)  # revealed: str
+reveal_type(Impl().impl)  # revealed: str
+reveal_type(Fake().fake)  # revealed: Unknown
+```
+
+## Overloading a full `py.typed`
+
+`foo-stubs` defines a full py.typed which is overloaded to partial by `foo-stubs/bar`
+
+```toml
+[environment]
+extra-paths = ["/packages"]
+```
+
+`/packages/foo-stubs/py.typed`:
+
+```text
+```
+
+`/packages/foo-stubs/bar/py.typed`:
+
+```text
+# Also testing permissive parsing
+partial/n
+```
+
+`/packages/foo-stubs/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/bar/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/bar/both.pyi`:
+
+```pyi
+class Both:
+    both: str
+    other: int
+```
+
+`/packages/foo/__init__.py`:
+
+```py
+```
+
+`/packages/foo/bar/__init__.py`:
+
+```py
+```
+
+`/packages/foo/bar/both.py`:
+
+```py
+class Both: ...
+```
+
+`/packages/foo/bar/impl.py`:
+
+```py
+class Impl:
+    impl: str
+    other: int
+```
+
+`main.py`:
+
+```py
+from foo.bar.both import Both
+from foo.bar.impl import Impl
+from foo.bar.fake import Fake  # error: "Cannot resolve"
+
+reveal_type(Both().both)  # revealed: str
+reveal_type(Impl().impl)  # revealed: str
+reveal_type(Fake().fake)  # revealed: Unknown
+```
+
+## Overloading a partial `py.typed`
+
+`foo-stubs` defines a partial py.typed which is overloaded to full by `foo-stubs/bar`
+
+```toml
+[environment]
+extra-paths = ["/packages"]
+```
+
+`/packages/foo-stubs/py.typed`:
+
+```text
+# Also testing permissive parsing
+pArTiAl\n
+```
+
+`/packages/foo-stubs/bar/py.typed`:
+
+```text
+```
+
+`/packages/foo-stubs/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/bar/__init__.pyi`:
+
+```pyi
+```
+
+`/packages/foo-stubs/bar/both.pyi`:
+
+```pyi
+class Both:
+    both: str
+    other: int
+```
+
+`/packages/foo/__init__.py`:
+
+```py
+```
+
+`/packages/foo/bar/__init__.py`:
+
+```py
+```
+
+`/packages/foo/bar/both.py`:
+
+```py
+class Both: ...
+```
+
+`/packages/foo/bar/impl.py`:
+
+```py
+class Impl:
+    impl: str
+    other: int
+```
+
+`main.py`:
+
+```py
+from foo.bar.both import Both
+from foo.bar.impl import Impl  # error: "Cannot resolve"
+from foo.bar.fake import Fake  # error: "Cannot resolve"
+
+reveal_type(Both().both)  # revealed: str
+reveal_type(Impl().impl)  # revealed: Unknown
+reveal_type(Fake().fake)  # revealed: Unknown
+```
+
+## Namespace stub with missing module
+
+Namespace stubs are always partial.
+
+This is a regression test for <https://github.com/astral-sh/ty/issues/520>.
+
+```toml
+[environment]
+extra-paths = ["/packages"]
+```
+
+`/packages/parent-stubs/foo/both.pyi`:
+
+```pyi
+class Both:
+    both: str
+    other: int
+```
+
+`/packages/parent/foo/both.py`:
+
+```py
+class Both: ...
+```
+
+`/packages/parent/foo/impl.py`:
+
+```py
+class Impl:
+    impl: str
+    other: int
+```
+
+`main.py`:
+
+```py
+from parent.foo.both import Both
+from parent.foo.impl import Impl
+from parent.foo.fake import Fake  # error: "Cannot resolve"
+
+reveal_type(Both().both)  # revealed: str
+reveal_type(Impl().impl)  # revealed: str
+reveal_type(Fake().fake)  # revealed: Unknown
+```

crates/ty_python_semantic/resources/mdtest/named_tuple.md

@@ -74,8 +74,16 @@ Person(3, "Eve", 99, "extra")
 # error: [invalid-argument-type]
 Person(id="3", name="Eve")
 
-# TODO: over-writing NamedTuple fields should be an error
+reveal_type(Person.id)  # revealed: property
+reveal_type(Person.name)  # revealed: property
+reveal_type(Person.age)  # revealed: property
+
+# TODO... the error is correct, but this is not the friendliest error message
+# for assigning to a read-only property :-)
+#
+# error: [invalid-assignment] "Invalid assignment to data descriptor attribute `id` on type `Person` with custom `__set__` method"
 alice.id = 42
+# error: [invalid-assignment]
 bob.age = None
 ```
 
@@ -94,28 +102,59 @@ reveal_type(alice2.name)  # revealed: @Todo(functional `NamedTuple` syntax)
 
 ### Definition
 
-TODO: Fields without default values should come before fields with.
+<!-- snapshot-diagnostics -->
+
+Fields without default values must come before fields with.
 
 ```py
 from typing import NamedTuple
 
 class Location(NamedTuple):
     altitude: float = 0.0
-    latitude: float  # this should be an error
+    # error: [invalid-named-tuple] "NamedTuple field without default value cannot follow field(s) with default value(s): Field `latitude` defined here without a default value"
+    latitude: float
+    # error: [invalid-named-tuple] "NamedTuple field without default value cannot follow field(s) with default value(s): Field `longitude` defined here without a default value"
     longitude: float
+
+class StrangeLocation(NamedTuple):
+    altitude: float
+    altitude: float = 0.0
+    altitude: float
+    altitude: float = 0.0
+    latitude: float  # error: [invalid-named-tuple]
+    longitude: float  # error: [invalid-named-tuple]
+
+class VeryStrangeLocation(NamedTuple):
+    altitude: float = 0.0
+    latitude: float  # error: [invalid-named-tuple]
+    longitude: float  # error: [invalid-named-tuple]
+    altitude: float = 0.0
 ```
 
 ### Multiple Inheritance
 
-Multiple inheritance is not supported for `NamedTuple` classes:
+<!-- snapshot-diagnostics -->
+
+Multiple inheritance is not supported for `NamedTuple` classes except with `Generic`:
 
 ```py
-from typing import NamedTuple
+from typing import NamedTuple, Protocol
 
-# This should ideally emit a diagnostic
+# error: [invalid-named-tuple] "NamedTuple class `C` cannot use multiple inheritance except with `Generic[]`"
 class C(NamedTuple, object):
     id: int
-    name: str
+
+# fmt: off
+
+class D(
+    int,  # error: [invalid-named-tuple]
+    NamedTuple
+): ...
+
+# fmt: on
+
+# error: [invalid-named-tuple]
+class E(NamedTuple, Protocol): ...
 ```
 
 ### Inheriting from a `NamedTuple`
@@ -151,9 +190,42 @@ from typing import NamedTuple
 class User(NamedTuple):
     id: int
     name: str
+    age: int | None
+    nickname: str
 
 class SuperUser(User):
-    id: int  # this should be an error
+    # TODO: this should be an error because it implies that the `id` attribute on
+    # `SuperUser` is mutable, but the read-only `id` property from the superclass
+    # has not been overridden in the class body
+    id: int
+
+    # this is fine; overriding a read-only attribute with a mutable one
+    # does not conflict with the Liskov Substitution Principle
+    name: str = "foo"
+
+    # this is also fine
+    @property
+    def age(self) -> int:
+        return super().age or 42
+
+    def now_called_robert(self):
+        self.name = "Robert"  # fine because overridden with a mutable attribute
+
+        # TODO: this should cause us to emit an error as we're assigning to a read-only property
+        # inherited from the `NamedTuple` superclass (requires https://github.com/astral-sh/ty/issues/159)
+        self.nickname = "Bob"
+
+james = SuperUser(0, "James", 42, "Jimmy")
+
+# fine because the property on the superclass was overridden with a mutable attribute
+# on the subclass
+james.name = "Robert"
+
+# TODO: the error is correct (can't assign to the read-only property inherited from the superclass)
+# but the error message could be friendlier :-)
+#
+# error: [invalid-assignment] "Invalid assignment to data descriptor attribute `nickname` on type `SuperUser` with custom `__set__` method"
+james.nickname = "Bob"
 ```
 
 ### Generic named tuples
@@ -164,13 +236,29 @@ python-version = "3.12"
 ```
 
 ```py
-from typing import NamedTuple
+from typing import NamedTuple, Generic, TypeVar
 
 class Property[T](NamedTuple):
     name: str
     value: T
 
 reveal_type(Property("height", 3.4))  # revealed: Property[float]
+reveal_type(Property.value)  # revealed: property
+reveal_type(Property.value.fget)  # revealed: (self, /) -> Unknown
+reveal_type(Property[str].value.fget)  # revealed: (self, /) -> str
+reveal_type(Property("height", 3.4).value)  # revealed: float
+
+T = TypeVar("T")
+
+class LegacyProperty(NamedTuple, Generic[T]):
+    name: str
+    value: T
+
+reveal_type(LegacyProperty("height", 42))  # revealed: LegacyProperty[int]
+reveal_type(LegacyProperty.value)  # revealed: property
+reveal_type(LegacyProperty.value.fget)  # revealed: (self, /) -> Unknown
+reveal_type(LegacyProperty[str].value.fget)  # revealed: (self, /) -> str
+reveal_type(LegacyProperty("height", 3.4).value)  # revealed: float
 ```
 
 ## Attributes on `NamedTuple`
@@ -186,7 +274,7 @@ class Person(NamedTuple):
 
 reveal_type(Person._field_defaults)  # revealed: dict[str, Any]
 reveal_type(Person._fields)  # revealed: tuple[str, ...]
-reveal_type(Person._make)  # revealed: bound method <class 'Person'>._make(iterable: Iterable[Any]) -> Self@_make
+reveal_type(Person._make)  # revealed: bound method <class 'Person'>._make(iterable: Iterable[Any]) -> Person
 reveal_type(Person._asdict)  # revealed: def _asdict(self) -> dict[str, Any]
 reveal_type(Person._replace)  # revealed: def _replace(self, **kwargs: Any) -> Self@_replace
 
@@ -211,6 +299,91 @@ alice = Person(1, "Alice", 42)
 bob = Person(2, "Bob")
 ```
 
+## The symbol `NamedTuple` itself
+
+At runtime, `NamedTuple` is a function, and we understand this:
+
+```py
+import types
+import typing
+
+def expects_functiontype(x: types.FunctionType): ...
+
+expects_functiontype(typing.NamedTuple)
+```
+
+This means we also understand that all attributes on function objects are available on the symbol
+`typing.NamedTuple`:
+
+```py
+reveal_type(typing.NamedTuple.__name__)  # revealed: str
+reveal_type(typing.NamedTuple.__qualname__)  # revealed: str
+reveal_type(typing.NamedTuple.__kwdefaults__)  # revealed: dict[str, Any] | None
+
+# TODO: this should cause us to emit a diagnostic and reveal `Unknown` (function objects don't have an `__mro__` attribute),
+# but the fact that we don't isn't actually a `NamedTuple` bug (https://github.com/astral-sh/ty/issues/986)
+reveal_type(typing.NamedTuple.__mro__)  # revealed: tuple[<class 'FunctionType'>, <class 'object'>]
+```
+
+By the normal rules, `NamedTuple` and `type[NamedTuple]` should not be valid in type expressions --
+there is no object at runtime that is an "instance of `NamedTuple`", nor is there any class at
+runtime that is a "subclass of `NamedTuple`" -- these are both impossible, since `NamedTuple` is a
+function and not a class. However, for compatibility with other type checkers, we allow `NamedTuple`
+in type expressions and understand it as describing an interface that all `NamedTuple` classes would
+satisfy:
+
+```py
+def expects_named_tuple(x: typing.NamedTuple):
+    reveal_type(x)  # revealed: tuple[object, ...] & NamedTupleLike
+    reveal_type(x._make)  # revealed: bound method type[NamedTupleLike]._make(iterable: Iterable[Any]) -> NamedTupleLike
+    reveal_type(x._replace)  # revealed: bound method NamedTupleLike._replace(**kwargs) -> NamedTupleLike
+    # revealed: Overload[(value: tuple[object, ...], /) -> tuple[object, ...], (value: tuple[_T@__add__, ...], /) -> tuple[object, ...]]
+    reveal_type(x.__add__)
+    reveal_type(x.__iter__)  # revealed: bound method tuple[object, ...].__iter__() -> Iterator[object]
+
+def _(y: type[typing.NamedTuple]):
+    reveal_type(y)  # revealed: @Todo(unsupported type[X] special form)
+
+# error: [invalid-type-form] "Special form `typing.NamedTuple` expected no type parameter"
+def _(z: typing.NamedTuple[int]): ...
+```
+
+Any instance of a `NamedTuple` class can therefore be passed for a function parameter that is
+annotated with `NamedTuple`:
+
+```py
+from typing import NamedTuple, Protocol, Iterable, Any
+from ty_extensions import static_assert, is_assignable_to
+
+class Point(NamedTuple):
+    x: int
+    y: int
+
+reveal_type(Point._make)  # revealed: bound method <class 'Point'>._make(iterable: Iterable[Any]) -> Point
+reveal_type(Point._asdict)  # revealed: def _asdict(self) -> dict[str, Any]
+reveal_type(Point._replace)  # revealed: def _replace(self, **kwargs: Any) -> Self@_replace
+
+static_assert(is_assignable_to(Point, NamedTuple))
+
+expects_named_tuple(Point(x=42, y=56))  # fine
+
+# error: [invalid-argument-type] "Argument to function `expects_named_tuple` is incorrect: Expected `tuple[object, ...] & NamedTupleLike`, found `tuple[Literal[1], Literal[2]]`"
+expects_named_tuple((1, 2))
+```
+
+The type described by `NamedTuple` in type expressions is understood as being assignable to
+`tuple[object, ...]` and `tuple[Any, ...]`:
+
+```py
+static_assert(is_assignable_to(NamedTuple, tuple))
+static_assert(is_assignable_to(NamedTuple, tuple[object, ...]))
+static_assert(is_assignable_to(NamedTuple, tuple[Any, ...]))
+
+def expects_tuple(x: tuple[object, ...]): ...
+def _(x: NamedTuple):
+    expects_tuple(x)  # fine
+```
+
 ## NamedTuple with custom `__getattr__`
 
 This is a regression test for <https://github.com/astral-sh/ty/issues/322>. Make sure that the

crates/ty_python_semantic/resources/mdtest/narrow/conditionals/nested.md

@@ -240,6 +240,21 @@ def f(x: str | None):
 
     # When there is a reassignment, any narrowing constraints on the place are invalidated in lazy scopes.
     x = None
+
+def f(x: str | None):
+    def _():
+        if x is not None:
+            def closure():
+                reveal_type(x)  # revealed: str | None
+    x = None
+
+def f(x: str | None):
+    class C:
+        def _():
+            if x is not None:
+                def closure():
+                    reveal_type(x)  # revealed: str
+        x = None  # This assignment is not visible in the inner lazy scope, so narrowing is still valid.
 ```
 
 If a variable defined in a private scope is never reassigned, narrowing remains in effect in the
@@ -256,6 +271,12 @@ def f(const: str | None):
             reveal_type(const)  # revealed: str
 
         [reveal_type(const) for _ in range(1)]  # revealed: str
+
+def f(const: str | None):
+    def _():
+        if const is not None:
+            def closure():
+                reveal_type(const)  # revealed: str
 ```
 
 And even if there is an attribute or subscript assignment to the variable, narrowing of the variable

crates/ty_python_semantic/resources/mdtest/narrow/type.md

@@ -3,10 +3,15 @@
 ## `type(x) is C`
 
 ```py
+from typing import final
+
 class A: ...
 class B: ...
 
-def _(x: A | B):
+@final
+class C: ...
+
+def _(x: A | B, y: A | C):
     if type(x) is A:
         reveal_type(x)  # revealed: A
     else:
@@ -14,20 +19,105 @@ def _(x: A | B):
         # of `x` could be a subclass of `A`, so we need
         # to infer the full union type:
         reveal_type(x)  # revealed: A | B
+
+    if type(y) is C:
+        reveal_type(y)  # revealed: C
+    else:
+        # here, however, inferring `A` is fine,
+        # because `C` is `@final`: no subclass of `A`
+        # and `C` could exist
+        reveal_type(y)  # revealed: A
+
+    if type(y) is A:
+        reveal_type(y)  # revealed: A
+    else:
+        # but here, `type(y)` could be a subclass of `A`,
+        # in which case the `type(y) is A` call would evaluate
+        # to `False` even if `y` was an instance of `A`,
+        # so narrowing cannot occur
+        reveal_type(y)  # revealed: A | C
 ```
 
 ## `type(x) is not C`
 
 ```py
+from typing import final
+
 class A: ...
 class B: ...
 
-def _(x: A | B):
+@final
+class C: ...
+
+def _(x: A | B, y: A | C):
     if type(x) is not A:
         # Same reasoning as above: no narrowing should occur here.
         reveal_type(x)  # revealed: A | B
     else:
         reveal_type(x)  # revealed: A
+
+    if type(y) is not C:
+        # same reasoning as above: narrowing *can* occur here because `C` is `@final`
+        reveal_type(y)  # revealed: A
+    else:
+        reveal_type(y)  # revealed: C
+
+    if type(y) is not A:
+        # same reasoning as above: narrowing *cannot* occur here
+        # because `A` is not `@final`
+        reveal_type(y)  # revealed: A | C
+    else:
+        reveal_type(y)  # revealed: A
+```
+
+## No narrowing for `type(x) is C[int]`
+
+At runtime, `type(x)` will never return a generic alias object (only ever a class-literal object),
+so no narrowing can occur if `type(x)` is compared with a generic alias object.
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+```py
+class A[T]: ...
+class B: ...
+
+def f(x: A[int] | B):
+    if type(x) is A[int]:
+        # this branch is actually unreachable -- we *could* reveal `Never` here!
+        reveal_type(x)  # revealed: A[int] | B
+    else:
+        reveal_type(x)  # revealed: A[int] | B
+
+    if type(x) is A:
+        # TODO: this should be `A[int]`, but `A[int] | B` would be better than `Never`
+        reveal_type(x)  # revealed: Never
+    else:
+        reveal_type(x)  # revealed: A[int] | B
+
+    if type(x) is B:
+        reveal_type(x)  # revealed: B
+    else:
+        reveal_type(x)  # revealed: A[int] | B
+
+    if type(x) is not A[int]:
+        reveal_type(x)  # revealed: A[int] | B
+    else:
+        # this branch is actually unreachable -- we *could* reveal `Never` here!
+        reveal_type(x)  # revealed: A[int] | B
+
+    if type(x) is not A:
+        reveal_type(x)  # revealed: A[int] | B
+    else:
+        # TODO: this should be `A[int]`, but `A[int] | B` would be better than `Never`
+        reveal_type(x)  # revealed: Never
+
+    if type(x) is not B:
+        reveal_type(x)  # revealed: A[int] | B
+    else:
+        reveal_type(x)  # revealed: B
 ```
 
 ## `type(x) == C`, `type(x) != C`
@@ -127,12 +217,23 @@ class B: ...
 
 def _[T](x: A | B):
     if type(x) is A[str]:
-        # `type()` never returns a generic alias, so `type(x)` cannot be `A[str]`
-        reveal_type(x)  # revealed: Never
+        # TODO: `type()` never returns a generic alias, so `type(x)` cannot be `A[str]`
+        reveal_type(x)  # revealed: A[int] | B
     else:
         reveal_type(x)  # revealed: A[int] | B
 ```
 
+## Narrowing for tuple
+
+An early version of <https://github.com/astral-sh/ruff/pull/19920> caused us to crash on this:
+
+```py
+def _(val):
+    if type(val) is tuple:
+        # TODO: better would be `Unknown & tuple[object, ...]`
+        reveal_type(val)  # revealed: Unknown & tuple[Unknown, ...]
+```
+
 ## Limitations
 
 ```py

crates/ty_python_semantic/resources/mdtest/pep695_type_aliases.md

@@ -64,6 +64,17 @@ x: MyIntOrStr = 1
 y: MyIntOrStr = None
 ```
 
+## Unpacking from a type alias
+
+```py
+type T = tuple[int, str]
+
+def f(x: T):
+    a, b = x
+    reveal_type(a)  # revealed: int
+    reveal_type(b)  # revealed: str
+```
+
 ## Generic type aliases
 
 ```py

crates/ty_python_semantic/resources/mdtest/protocols.md

@@ -150,6 +150,14 @@ class AlsoInvalid(MyProtocol, OtherProtocol, NotAProtocol, Protocol): ...
 
 # revealed: tuple[<class 'AlsoInvalid'>, <class 'MyProtocol'>, <class 'OtherProtocol'>, <class 'NotAProtocol'>, typing.Protocol, typing.Generic, <class 'object'>]
 reveal_type(AlsoInvalid.__mro__)
+
+class NotAGenericProtocol[T]: ...
+
+# error: [invalid-protocol] "Protocol class `StillInvalid` cannot inherit from non-protocol class `NotAGenericProtocol`"
+class StillInvalid(NotAGenericProtocol[int], Protocol): ...
+
+# revealed: tuple[<class 'StillInvalid'>, <class 'NotAGenericProtocol[int]'>, typing.Protocol, typing.Generic, <class 'object'>]
+reveal_type(StillInvalid.__mro__)
 ```
 
 But two exceptions to this rule are `object` and `Generic`:
@@ -347,7 +355,9 @@ And as a corollary, `type[MyProtocol]` can also be called:
 
 ```py
 def f(x: type[MyProtocol]):
-    reveal_type(x())  # revealed: MyProtocol
+    # TODO: add a `reveal_type` call here once it's no longer a `Todo` type
+    # (which doesn't work well with snapshots)
+    x()
 ```
 
 ## Members of a protocol
@@ -387,7 +397,7 @@ To see the kinds and types of the protocol members, you can use the debugging ai
 
 ```py
 from ty_extensions import reveal_protocol_interface
-from typing import SupportsIndex, SupportsAbs
+from typing import SupportsIndex, SupportsAbs, ClassVar
 
 # error: [revealed-type] "Revealed protocol interface: `{"method_member": MethodMember(`(self) -> bytes`), "x": AttributeMember(`int`), "y": PropertyMember { getter: `def y(self) -> str` }, "z": PropertyMember { getter: `def z(self) -> int`, setter: `def z(self, z: int) -> None` }}`"
 reveal_protocol_interface(Foo)
@@ -405,6 +415,33 @@ reveal_protocol_interface("foo")
 #
 # error: [invalid-argument-type] "Invalid argument to `reveal_protocol_interface`: Only protocol classes can be passed to `reveal_protocol_interface`"
 reveal_protocol_interface(SupportsAbs[int])
+
+class BaseProto(Protocol):
+    def member(self) -> int: ...
+
+class SubProto(BaseProto, Protocol):
+    def member(self) -> bool: ...
+
+# error: [revealed-type] "Revealed protocol interface: `{"member": MethodMember(`(self) -> int`)}`"
+reveal_protocol_interface(BaseProto)
+
+# error: [revealed-type] "Revealed protocol interface: `{"member": MethodMember(`(self) -> bool`)}`"
+reveal_protocol_interface(SubProto)
+
+class ProtoWithClassVar(Protocol):
+    x: ClassVar[int]
+
+# error: [revealed-type] "Revealed protocol interface: `{"x": AttributeMember(`int`; ClassVar)}`"
+reveal_protocol_interface(ProtoWithClassVar)
+
+class ProtocolWithDefault(Protocol):
+    x: int = 0
+
+# We used to incorrectly report this as having an `x: Literal[0]` member;
+# declared types should take priority over inferred types for protocol interfaces!
+#
+# error: [revealed-type] "Revealed protocol interface: `{"x": AttributeMember(`int`)}`"
+reveal_protocol_interface(ProtocolWithDefault)
 ```
 
 Certain special attributes and methods are not considered protocol members at runtime, and should
@@ -445,6 +482,8 @@ reveal_type(get_protocol_members(Baz2))
 
 ## Protocol members in statically known branches
 
+<!-- snapshot-diagnostics -->
+
 The list of protocol members does not include any members declared in branches that are statically
 known to be unreachable:
 
@@ -455,7 +494,7 @@ python-version = "3.9"
 
 ```py
 import sys
-from typing_extensions import Protocol, get_protocol_members
+from typing_extensions import Protocol, get_protocol_members, reveal_type
 
 class Foo(Protocol):
     if sys.version_info >= (3, 10):
@@ -464,7 +503,7 @@ class Foo(Protocol):
         def c(self) -> None: ...
     else:
         d: int
-        e = 56
+        e = 56  # error: [ambiguous-protocol-member]
         def f(self) -> None: ...
 
 reveal_type(get_protocol_members(Foo))  # revealed: frozenset[Literal["d", "e", "f"]]
@@ -613,13 +652,26 @@ class HasXWithDefault(Protocol):
 class FooWithZero:
     x: int = 0
 
-# TODO: these should pass
-static_assert(is_subtype_of(FooWithZero, HasXWithDefault))  # error: [static-assert-error]
-static_assert(is_assignable_to(FooWithZero, HasXWithDefault))  # error: [static-assert-error]
-static_assert(not is_subtype_of(Foo, HasXWithDefault))
-static_assert(not is_assignable_to(Foo, HasXWithDefault))
-static_assert(not is_subtype_of(Qux, HasXWithDefault))
-static_assert(not is_assignable_to(Qux, HasXWithDefault))
+static_assert(is_subtype_of(FooWithZero, HasXWithDefault))
+static_assert(is_assignable_to(FooWithZero, HasXWithDefault))
+
+# TODO: whether or not any of these four assertions should pass is not clearly specified.
+#
+# A test in the typing conformance suite implies that they all should:
+# that a nominal class with an instance attribute `x`
+# (*without* a default value on the class body)
+# should be understood as satisfying a protocol that has an attribute member `x`
+# even if the protocol's `x` member has a default value on the class body.
+#
+# See <https://github.com/python/typing/blob/d4f39b27a4a47aac8b6d4019e1b0b5b3156fabdc/conformance/tests/protocols_definition.py#L56-L79>.
+#
+# The implications of this for meta-protocols are not clearly spelled out, however,
+# and the fact that attribute members on protocols can have defaults is only mentioned
+# in a throwaway comment in the spec's prose.
+static_assert(is_subtype_of(Foo, HasXWithDefault))
+static_assert(is_assignable_to(Foo, HasXWithDefault))
+static_assert(is_subtype_of(Qux, HasXWithDefault))
+static_assert(is_assignable_to(Qux, HasXWithDefault))
 
 class HasClassVarX(Protocol):
     x: ClassVar[int]
@@ -747,9 +799,9 @@ def f(arg: HasXWithDefault):
 ```
 
 Assignments in a class body of a protocol -- of any kind -- are not permitted by ty unless the
-symbol being assigned to is also explicitly declared in the protocol's class body. Note that this is
-stricter validation of protocol members than many other type checkers currently apply (as of
-2025/04/21).
+symbol being assigned to is also explicitly declared in the body of the protocol class or one of its
+superclasses. Note that this is stricter validation of protocol members than many other type
+checkers currently apply (as of 2025/04/21).
 
 The reason for this strict validation is that undeclared variables in the class body would lead to
 an ambiguous interface being declared by the protocol.
@@ -773,24 +825,75 @@ class LotsOfBindings(Protocol):
 
     class Nested: ...  # also weird, but we should also probably allow it
     class NestedProtocol(Protocol): ...  # same here...
-    e = 72  # TODO: this should error with `[invalid-protocol]` (`e` is not declared)
+    e = 72  # error: [ambiguous-protocol-member]
 
-    f, g = (1, 2)  # TODO: this should error with `[invalid-protocol]` (`f` and `g` are not declared)
+    # error: [ambiguous-protocol-member] "Consider adding an annotation, e.g. `f: int = ...`"
+    # error: [ambiguous-protocol-member] "Consider adding an annotation, e.g. `g: int = ...`"
+    f, g = (1, 2)
 
-    h: int = (i := 3)  # TODO: this should error with `[invalid-protocol]` (`i` is not declared)
+    h: int = (i := 3)  # error: [ambiguous-protocol-member]
 
-    for j in range(42):  # TODO: this should error with `[invalid-protocol]` (`j` is not declared)
+    for j in range(42):  # error: [ambiguous-protocol-member]
         pass
 
-    with MyContext() as k:  # TODO: this should error with `[invalid-protocol]` (`k` is not declared)
+    with MyContext() as k:  # error: [ambiguous-protocol-member]
         pass
 
     match object():
-        case l:  # TODO: this should error with `[invalid-protocol]` (`l` is not declared)
+        case l:  # error: [ambiguous-protocol-member]
             ...
 
 # revealed: frozenset[Literal["Nested", "NestedProtocol", "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l"]]
 reveal_type(get_protocol_members(LotsOfBindings))
+
+class Foo(Protocol):
+    a: int
+
+class Bar(Foo, Protocol):
+    a = 42  # fine, because it's declared in the superclass
+
+reveal_type(get_protocol_members(Bar))  # revealed: frozenset[Literal["a"]]
+```
+
+A binding-without-declaration will not be reported if it occurs in a branch that we can statically
+determine to be unreachable. The reason is that we don't consider it to be a protocol member at all
+if all definitions for the variable are in unreachable blocks:
+
+```py
+import sys
+
+class Protocol694(Protocol):
+    if sys.version_info > (3, 694):
+        x = 42  # no error!
+```
+
+If there are multiple bindings of the variable in the class body, however, and at least one of the
+bindings occurs in a block of code that is understood to be (possibly) reachable, a diagnostic will
+be reported. The diagnostic will be attached to the first binding that occurs in the class body,
+even if that first definition occurs in an unreachable block:
+
+```py
+class Protocol695(Protocol):
+    if sys.version_info > (3, 695):
+        x = 42
+    else:
+        x = 42
+
+    x = 56  # error: [ambiguous-protocol-member]
+```
+
+In order for the variable to be considered declared, the declaration of the variable must also take
+place in a block of code that is understood to be (possibly) reachable:
+
+```py
+class Protocol696(Protocol):
+    if sys.version_info > (3, 696):
+        x: int
+    else:
+        x = 42  # error: [ambiguous-protocol-member]
+        y: int
+
+    y = 56  # no error
 ```
 
 Attribute members are allowed to have assignments in methods on the protocol class, just like
@@ -893,6 +996,40 @@ static_assert(not is_assignable_to(HasX, Foo))
 static_assert(not is_subtype_of(HasX, Foo))
 ```
 
+## Diagnostics for protocols with invalid attribute members
+
+This is a short appendix to the previous section with the `snapshot-diagnostics` directive enabled
+(enabling snapshots for the previous section in its entirety would lead to a huge snapshot, since
+it's a large section).
+
+<!-- snapshot-diagnostics -->
+
+```py
+from typing import Protocol
+
+def coinflip() -> bool:
+    return True
+
+class A(Protocol):
+    # The `x` and `y` members attempt to use Python-2-style type comments
+    # to indicate that the type should be `int | None` and `str` respectively,
+    # but we don't support those
+
+    # error: [ambiguous-protocol-member]
+    a = None  # type: int
+    # error: [ambiguous-protocol-member]
+    b = ...  # type: str
+
+    if coinflip():
+        c = 1  # error: [ambiguous-protocol-member]
+    else:
+        c = 2
+
+    # error: [ambiguous-protocol-member]
+    for d in range(42):
+        pass
+```
+
 ## Equivalence of protocols
 
 Two protocols are considered equivalent types if they specify the same interface, even if they have
@@ -1923,7 +2060,7 @@ def _(r: Recursive):
     reveal_type(r.t)  # revealed: tuple[int, tuple[str, Recursive]]
     reveal_type(r.callable1)  # revealed: (int, /) -> Recursive
     reveal_type(r.callable2)  # revealed: (Recursive, /) -> int
-    reveal_type(r.subtype_of)  # revealed: type[Recursive]
+    reveal_type(r.subtype_of)  # revealed: @Todo(type[T] for protocols)
     reveal_type(r.generic)  # revealed: GenericC[Recursive]
     reveal_type(r.method(r))  # revealed: Recursive
     reveal_type(r.nested)  # revealed: Recursive | ((Recursive, tuple[Recursive, Recursive], /) -> Recursive)
@@ -2061,6 +2198,86 @@ def f(value: Iterator):
     cast(Iterator, value)  # error: [redundant-cast]
 ```
 
+## Meta-protocols
+
+Where `P` is a protocol type, a class object `N` can be said to inhabit the type `type[P]` if:
+
+- All `ClassVar` members on `P` exist on the class object `N`
+- All method members on `P` exist on the class object `N`
+- Instantiating `N` creates an object that would satisfy the protocol `P`
+
+Currently meta-protocols are not fully supported by ty, but we try to keep false positives to a
+minimum in the meantime.
+
+```py
+from typing import Protocol, ClassVar
+from ty_extensions import static_assert, is_assignable_to, TypeOf, is_subtype_of
+
+class Foo(Protocol):
+    x: int
+    y: ClassVar[str]
+    def method(self) -> bytes: ...
+
+def _(f: type[Foo]):
+    reveal_type(f)  # revealed: type[@Todo(type[T] for protocols)]
+
+    # TODO: we should emit `unresolved-attribute` here: although we would accept this for a
+    # nominal class, we would see any class `N` as inhabiting `Foo` if it had an implicit
+    # instance attribute `x`, and implicit instance attributes are rarely bound on the class
+    # object.
+    reveal_type(f.x)  # revealed: @Todo(type[T] for protocols)
+
+    # TODO: should be `str`
+    reveal_type(f.y)  # revealed: @Todo(type[T] for protocols)
+    f.y = "foo"  # fine
+
+    # TODO: should be `Callable[[Foo], bytes]`
+    reveal_type(f.method)  # revealed: @Todo(type[T] for protocols)
+
+class Bar: ...
+
+# TODO: these should pass
+static_assert(not is_assignable_to(type[Bar], type[Foo]))  # error: [static-assert-error]
+static_assert(not is_assignable_to(TypeOf[Bar], type[Foo]))  # error: [static-assert-error]
+
+class Baz:
+    x: int
+    y: ClassVar[str] = "foo"
+    def method(self) -> bytes:
+        return b"foo"
+
+static_assert(is_assignable_to(type[Baz], type[Foo]))
+static_assert(is_assignable_to(TypeOf[Baz], type[Foo]))
+
+# TODO: these should pass
+static_assert(is_subtype_of(type[Baz], type[Foo]))  # error: [static-assert-error]
+static_assert(is_subtype_of(TypeOf[Baz], type[Foo]))  # error: [static-assert-error]
+```
+
+## Regression test for `ClassVar` members in stubs
+
+In an early version of our protocol implementation, we didn't retain the `ClassVar` qualifier for
+protocols defined in stub files.
+
+`stub.pyi`:
+
+```pyi
+from typing import ClassVar, Protocol
+
+class Foo(Protocol):
+    x: ClassVar[int]
+```
+
+`main.py`:
+
+```py
+from stub import Foo
+from ty_extensions import reveal_protocol_interface
+
+# error: [revealed-type] "Revealed protocol interface: `{"x": AttributeMember(`int`; ClassVar)}`"
+reveal_protocol_interface(Foo)
+```
+
 ## TODO
 
 Add tests for:

crates/ty_python_semantic/resources/mdtest/snapshots/dataclasses.md_-_Dataclasses_-_`dataclasses.KW_ONLY…_(dd1b8f2f71487f16).snap

@@ -49,6 +49,22 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/dataclasses/dataclasses.
 35 |         y: str
 36 |         _2: KW_ONLY
 37 |         z: float
+38 | from dataclasses import dataclass, KW_ONLY
+39 | 
+40 | @dataclass
+41 | class D:
+42 |     x: int
+43 |     _: KW_ONLY
+44 |     y: str
+45 | 
+46 | @dataclass
+47 | class E(D):
+48 |     z: bytes
+49 | 
+50 | # This should work: x=1 (positional), z=b"foo" (positional), y="foo" (keyword-only)
+51 | E(1, b"foo", y="foo")
+52 | 
+53 | reveal_type(E.__init__)  # revealed: (self: E, x: int, z: bytes, *, y: str) -> None
 ```
 
 # Diagnostics
@@ -141,3 +157,15 @@ info: `KW_ONLY` fields: `_1`, `_2`
 info: rule `duplicate-kw-only` is enabled by default
 
 ```
+
+```
+info[revealed-type]: Revealed type
+  --> src/mdtest_snippet.py:53:13
+   |
+51 | E(1, b"foo", y="foo")
+52 |
+53 | reveal_type(E.__init__)  # revealed: (self: E, x: int, z: bytes, *, y: str) -> None
+   |             ^^^^^^^^^^ `(self: E, x: int, z: bytes, *, y: str) -> None`
+   |
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_await.md_-_Invalid_await_diagno…_-_Basic_(f15db7dc447d0795).snap

@@ -0,0 +1,41 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_await.md - Invalid await diagnostics - Basic
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_await.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | async def main() -> None:
+2 |     await 1  # error: [invalid-await]
+```
+
+# Diagnostics
+
+```
+error[invalid-await]: `Literal[1]` is not awaitable
+   --> src/mdtest_snippet.py:2:11
+    |
+  1 | async def main() -> None:
+  2 |     await 1  # error: [invalid-await]
+    |           ^
+    |
+   ::: stdlib/builtins.pyi:337:7
+    |
+335 | _LiteralInteger = _PositiveInteger | _NegativeInteger | Literal[0]  # noqa: Y026  # TODO: Use TypeAlias once mypy bugs are fixed
+336 |
+337 | class int:
+    |       --- type defined here
+338 |     """int([x]) -> integer
+339 |     int(x, base=10) -> integer
+    |
+info: `__await__` is missing
+info: rule `invalid-await` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_await.md_-_Invalid_await_diagno…_-_Custom_type_with_mis…_(9ce1ee3cd1c9c8d1).snap

@@ -0,0 +1,41 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_await.md - Invalid await diagnostics - Custom type with missing `__await__`
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_await.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | class MissingAwait:
+2 |     pass
+3 | 
+4 | async def main() -> None:
+5 |     await MissingAwait()  # error: [invalid-await]
+```
+
+# Diagnostics
+
+```
+error[invalid-await]: `MissingAwait` is not awaitable
+ --> src/mdtest_snippet.py:5:11
+  |
+4 | async def main() -> None:
+5 |     await MissingAwait()  # error: [invalid-await]
+  |           ^^^^^^^^^^^^^^
+  |
+ ::: src/mdtest_snippet.py:1:7
+  |
+1 | class MissingAwait:
+  |       ------------ type defined here
+2 |     pass
+  |
+info: `__await__` is missing
+info: rule `invalid-await` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_await.md_-_Invalid_await_diagno…_-_Custom_type_with_pos…_(e3444b7a7f960d04).snap

@@ -0,0 +1,47 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_await.md - Invalid await diagnostics - Custom type with possibly unbound `__await__`
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_await.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | from datetime import datetime
+2 | 
+3 | class PossiblyUnbound:
+4 |     if datetime.today().weekday() == 0:
+5 |         def __await__(self):
+6 |             yield
+7 | 
+8 | async def main() -> None:
+9 |     await PossiblyUnbound()  # error: [invalid-await]
+```
+
+# Diagnostics
+
+```
+error[invalid-await]: `PossiblyUnbound` is not awaitable
+ --> src/mdtest_snippet.py:9:11
+  |
+8 | async def main() -> None:
+9 |     await PossiblyUnbound()  # error: [invalid-await]
+  |           ^^^^^^^^^^^^^^^^^
+  |
+ ::: src/mdtest_snippet.py:5:13
+  |
+3 | class PossiblyUnbound:
+4 |     if datetime.today().weekday() == 0:
+5 |         def __await__(self):
+  |             --------------- method defined here
+6 |             yield
+  |
+info: `__await__` is possibly unbound
+info: rule `invalid-await` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_await.md_-_Invalid_await_diagno…_-_Invalid_union_return…_(fedf62ffaca0f2d7).snap

@@ -0,0 +1,45 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_await.md - Invalid await diagnostics - Invalid union return type
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_await.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+ 1 | import typing
+ 2 | from datetime import datetime
+ 3 | 
+ 4 | class UnawaitableUnion:
+ 5 |     if datetime.today().weekday() == 6:
+ 6 | 
+ 7 |         def __await__(self) -> typing.Generator[typing.Any, None, None]:
+ 8 |             yield
+ 9 |     else:
+10 | 
+11 |         def __await__(self) -> int:
+12 |             return 5
+13 | 
+14 | async def main() -> None:
+15 |     await UnawaitableUnion()  # error: [invalid-await]
+```
+
+# Diagnostics
+
+```
+error[invalid-await]: `UnawaitableUnion` is not awaitable
+  --> src/mdtest_snippet.py:15:11
+   |
+14 | async def main() -> None:
+15 |     await UnawaitableUnion()  # error: [invalid-await]
+   |           ^^^^^^^^^^^^^^^^^^
+   |
+info: `__await__` returns `Generator[Any, None, None] | int`, which is not a valid iterator
+info: rule `invalid-await` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_await.md_-_Invalid_await_diagno…_-_Non-callable_`__awai…_(d78580fb6720e4ea).snap

@@ -0,0 +1,35 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_await.md - Invalid await diagnostics - Non-callable `__await__`
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_await.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | class NonCallableAwait:
+2 |     __await__ = 42
+3 | 
+4 | async def main() -> None:
+5 |     await NonCallableAwait()  # error: [invalid-await]
+```
+
+# Diagnostics
+
+```
+error[invalid-await]: `NonCallableAwait` is not awaitable
+ --> src/mdtest_snippet.py:5:11
+  |
+4 | async def main() -> None:
+5 |     await NonCallableAwait()  # error: [invalid-await]
+  |           ^^^^^^^^^^^^^^^^^^
+  |
+info: `__await__` is possibly not callable
+info: rule `invalid-await` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_await.md_-_Invalid_await_diagno…_-_`__await__`_definiti…_(15b05c126b6ae968).snap

@@ -0,0 +1,43 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_await.md - Invalid await diagnostics - `__await__` definition with extra arguments
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_await.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | class InvalidAwaitArgs:
+2 |     def __await__(self, value: int):
+3 |         yield value
+4 | 
+5 | async def main() -> None:
+6 |     await InvalidAwaitArgs()  # error: [invalid-await]
+```
+
+# Diagnostics
+
+```
+error[invalid-await]: `InvalidAwaitArgs` is not awaitable
+ --> src/mdtest_snippet.py:6:11
+  |
+5 | async def main() -> None:
+6 |     await InvalidAwaitArgs()  # error: [invalid-await]
+  |           ^^^^^^^^^^^^^^^^^^
+  |
+ ::: src/mdtest_snippet.py:2:18
+  |
+1 | class InvalidAwaitArgs:
+2 |     def __await__(self, value: int):
+  |                  ------------------ parameters here
+3 |         yield value
+  |
+info: `__await__` requires arguments and cannot be called implicitly
+info: rule `invalid-await` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_await.md_-_Invalid_await_diagno…_-_`__await__`_definiti…_(ccb69f512135dd61).snap

@@ -0,0 +1,43 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_await.md - Invalid await diagnostics - `__await__` definition with explicit invalid return type
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_await.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | class InvalidAwaitReturn:
+2 |     def __await__(self) -> int:
+3 |         return 5
+4 | 
+5 | async def main() -> None:
+6 |     await InvalidAwaitReturn()  # error: [invalid-await]
+```
+
+# Diagnostics
+
+```
+error[invalid-await]: `InvalidAwaitReturn` is not awaitable
+ --> src/mdtest_snippet.py:6:11
+  |
+5 | async def main() -> None:
+6 |     await InvalidAwaitReturn()  # error: [invalid-await]
+  |           ^^^^^^^^^^^^^^^^^^^^
+  |
+ ::: src/mdtest_snippet.py:2:9
+  |
+1 | class InvalidAwaitReturn:
+2 |     def __await__(self) -> int:
+  |         ---------------------- method defined here
+3 |         return 5
+  |
+info: `__await__` returns `int`, which is not a valid iterator
+info: rule `invalid-await` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/named_tuple.md_-_`NamedTuple`_-_`typing.NamedTuple`_-_Definition_(bbf79630502e65e9).snap

@@ -0,0 +1,140 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: named_tuple.md - `NamedTuple` - `typing.NamedTuple` - Definition
+mdtest path: crates/ty_python_semantic/resources/mdtest/named_tuple.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+ 1 | from typing import NamedTuple
+ 2 | 
+ 3 | class Location(NamedTuple):
+ 4 |     altitude: float = 0.0
+ 5 |     # error: [invalid-named-tuple] "NamedTuple field without default value cannot follow field(s) with default value(s): Field `latitude` defined here without a default value"
+ 6 |     latitude: float
+ 7 |     # error: [invalid-named-tuple] "NamedTuple field without default value cannot follow field(s) with default value(s): Field `longitude` defined here without a default value"
+ 8 |     longitude: float
+ 9 | 
+10 | class StrangeLocation(NamedTuple):
+11 |     altitude: float
+12 |     altitude: float = 0.0
+13 |     altitude: float
+14 |     altitude: float = 0.0
+15 |     latitude: float  # error: [invalid-named-tuple]
+16 |     longitude: float  # error: [invalid-named-tuple]
+17 | 
+18 | class VeryStrangeLocation(NamedTuple):
+19 |     altitude: float = 0.0
+20 |     latitude: float  # error: [invalid-named-tuple]
+21 |     longitude: float  # error: [invalid-named-tuple]
+22 |     altitude: float = 0.0
+```
+
+# Diagnostics
+
+```
+error[invalid-named-tuple]: NamedTuple field without default value cannot follow field(s) with default value(s)
+ --> src/mdtest_snippet.py:4:5
+  |
+3 | class Location(NamedTuple):
+4 |     altitude: float = 0.0
+  |     --------------------- Earlier field `altitude` defined here with a default value
+5 |     # error: [invalid-named-tuple] "NamedTuple field without default value cannot follow field(s) with default value(s): Field `latitud…
+6 |     latitude: float
+  |     ^^^^^^^^ Field `latitude` defined here without a default value
+7 |     # error: [invalid-named-tuple] "NamedTuple field without default value cannot follow field(s) with default value(s): Field `longitu…
+8 |     longitude: float
+  |
+info: rule `invalid-named-tuple` is enabled by default
+
+```
+
+```
+error[invalid-named-tuple]: NamedTuple field without default value cannot follow field(s) with default value(s)
+  --> src/mdtest_snippet.py:4:5
+   |
+ 3 | class Location(NamedTuple):
+ 4 |     altitude: float = 0.0
+   |     --------------------- Earlier field `altitude` defined here with a default value
+ 5 |     # error: [invalid-named-tuple] "NamedTuple field without default value cannot follow field(s) with default value(s): Field `latitu…
+ 6 |     latitude: float
+ 7 |     # error: [invalid-named-tuple] "NamedTuple field without default value cannot follow field(s) with default value(s): Field `longit…
+ 8 |     longitude: float
+   |     ^^^^^^^^^ Field `longitude` defined here without a default value
+ 9 |
+10 | class StrangeLocation(NamedTuple):
+   |
+info: rule `invalid-named-tuple` is enabled by default
+
+```
+
+```
+error[invalid-named-tuple]: NamedTuple field without default value cannot follow field(s) with default value(s)
+  --> src/mdtest_snippet.py:14:5
+   |
+12 |     altitude: float = 0.0
+13 |     altitude: float
+14 |     altitude: float = 0.0
+   |     --------------------- Earlier field `altitude` defined here with a default value
+15 |     latitude: float  # error: [invalid-named-tuple]
+   |     ^^^^^^^^ Field `latitude` defined here without a default value
+16 |     longitude: float  # error: [invalid-named-tuple]
+   |
+info: rule `invalid-named-tuple` is enabled by default
+
+```
+
+```
+error[invalid-named-tuple]: NamedTuple field without default value cannot follow field(s) with default value(s)
+  --> src/mdtest_snippet.py:14:5
+   |
+12 |     altitude: float = 0.0
+13 |     altitude: float
+14 |     altitude: float = 0.0
+   |     --------------------- Earlier field `altitude` defined here with a default value
+15 |     latitude: float  # error: [invalid-named-tuple]
+16 |     longitude: float  # error: [invalid-named-tuple]
+   |     ^^^^^^^^^ Field `longitude` defined here without a default value
+17 |
+18 | class VeryStrangeLocation(NamedTuple):
+   |
+info: rule `invalid-named-tuple` is enabled by default
+
+```
+
+```
+error[invalid-named-tuple]: NamedTuple field without default value cannot follow field(s) with default value(s)
+  --> src/mdtest_snippet.py:20:5
+   |
+18 | class VeryStrangeLocation(NamedTuple):
+19 |     altitude: float = 0.0
+20 |     latitude: float  # error: [invalid-named-tuple]
+   |     ^^^^^^^^ Field `latitude` defined here without a default value
+21 |     longitude: float  # error: [invalid-named-tuple]
+22 |     altitude: float = 0.0
+   |
+info: Earlier field `altitude` was defined with a default value
+info: rule `invalid-named-tuple` is enabled by default
+
+```
+
+```
+error[invalid-named-tuple]: NamedTuple field without default value cannot follow field(s) with default value(s)
+  --> src/mdtest_snippet.py:21:5
+   |
+19 |     altitude: float = 0.0
+20 |     latitude: float  # error: [invalid-named-tuple]
+21 |     longitude: float  # error: [invalid-named-tuple]
+   |     ^^^^^^^^^ Field `longitude` defined here without a default value
+22 |     altitude: float = 0.0
+   |
+info: Earlier field `altitude` was defined with a default value
+info: rule `invalid-named-tuple` is enabled by default
+
+```