[ty] Track narrowing unions to prevent exponential blowup

When inferring a call expression with a union type context, we try narrowing
to each element of the union. If nested calls have the same union as their
parameter type, this would lead to exponential blowup. By tracking which
unions we're already narrowing against, we skip redundant nested narrowing.

On a synthetic benchmark with nested `list_schema()` calls:
- 4-level nesting: >120s → 0.13s

.github/mypy-primer-ty.toml

@@ -4,5 +4,6 @@
 # Enable off-by-default rules.
 [rules]
 possibly-unresolved-reference = "warn"
+possibly-missing-import = "warn"
 unused-ignore-comment = "warn"
 division-by-zero = "warn"

.github/workflows/ty-ecosystem-analyzer.yaml

@@ -67,7 +67,7 @@ jobs:
 
           cd ..
 
-          uv tool install "git+https://github.com/astral-sh/ecosystem-analyzer@55df3c868f3fa9ab34cff0498dd6106722aac205"
+          uv tool install "git+https://github.com/astral-sh/ecosystem-analyzer@2e1816eac09c90140b1ba51d19afc5f59da460f5"
 
           ecosystem-analyzer \
             --repository ruff \

.github/workflows/ty-ecosystem-report.yaml

@@ -52,7 +52,7 @@ jobs:
 
           cd ..
 
-          uv tool install "git+https://github.com/astral-sh/ecosystem-analyzer@55df3c868f3fa9ab34cff0498dd6106722aac205"
+          uv tool install "git+https://github.com/astral-sh/ecosystem-analyzer@2e1816eac09c90140b1ba51d19afc5f59da460f5"
 
           ecosystem-analyzer \
             --verbose \

CHANGELOG.md

@@ -1,5 +1,54 @@
 # Changelog
 
+## 0.14.10
+
+Released on 2025-12-18.
+
+### Preview features
+
+- [formatter] Fluent formatting of method chains ([#21369](https://github.com/astral-sh/ruff/pull/21369))
+- [formatter] Keep lambda parameters on one line and parenthesize the body if it expands ([#21385](https://github.com/astral-sh/ruff/pull/21385))
+- \[`flake8-implicit-str-concat`\] New rule to prevent implicit string concatenation in collections (`ISC004`) ([#21972](https://github.com/astral-sh/ruff/pull/21972))
+- \[`flake8-use-pathlib`\] Make fixes unsafe when types change in compound statements (`PTH104`, `PTH105`, `PTH109`, `PTH115`) ([#22009](https://github.com/astral-sh/ruff/pull/22009))
+- \[`refurb`\] Extend support for `Path.open` (`FURB101`, `FURB103`) ([#21080](https://github.com/astral-sh/ruff/pull/21080))
+
+### Bug fixes
+
+- \[`pyupgrade`\] Fix parsing named Unicode escape sequences (`UP032`) ([#21901](https://github.com/astral-sh/ruff/pull/21901))
+
+### Rule changes
+
+- \[`eradicate`\] Ignore `ruff:disable` and `ruff:enable` comments in `ERA001` ([#22038](https://github.com/astral-sh/ruff/pull/22038))
+- \[`flake8-pytest-style`\] Allow `match` and `check` keyword arguments without an expected exception type (`PT010`) ([#21964](https://github.com/astral-sh/ruff/pull/21964))
+- [syntax-errors] Annotated name cannot be global ([#20868](https://github.com/astral-sh/ruff/pull/20868))
+
+### Documentation
+
+- Add `uv` and `ty` to the Ruff README ([#21996](https://github.com/astral-sh/ruff/pull/21996))
+- Document known lambda formatting deviations from Black ([#21954](https://github.com/astral-sh/ruff/pull/21954))
+- Update `setup.md` ([#22024](https://github.com/astral-sh/ruff/pull/22024))
+- \[`flake8-bandit`\] Fix broken link (`S704`) ([#22039](https://github.com/astral-sh/ruff/pull/22039))
+
+### Other changes
+
+- Fix playground Share button showing "Copied!" before clipboard copy completes ([#21942](https://github.com/astral-sh/ruff/pull/21942))
+
+### Contributors
+
+- [@dylwil3](https://github.com/dylwil3)
+- [@charliecloudberry](https://github.com/charliecloudberry)
+- [@charliermarsh](https://github.com/charliermarsh)
+- [@chirizxc](https://github.com/chirizxc)
+- [@ntBre](https://github.com/ntBre)
+- [@zanieb](https://github.com/zanieb)
+- [@amyreese](https://github.com/amyreese)
+- [@hauntsaninja](https://github.com/hauntsaninja)
+- [@11happy](https://github.com/11happy)
+- [@mahiro72](https://github.com/mahiro72)
+- [@MichaReiser](https://github.com/MichaReiser)
+- [@phongddo](https://github.com/phongddo)
+- [@PeterJCLaw](https://github.com/PeterJCLaw)
+
 ## 0.14.9
 
 Released on 2025-12-11.

Cargo.lock

@@ -1004,27 +1004,6 @@ dependencies = [
  "crypto-common",
 ]
 
-[[package]]
-name = "dir-test"
-version = "0.4.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "62c013fe825864f3e4593f36426c1fa7a74f5603f13ca8d1af7a990c1cd94a79"
-dependencies = [
- "dir-test-macros",
-]
-
-[[package]]
-name = "dir-test-macros"
-version = "0.4.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d42f54d7b4a6bc2400fe5b338e35d1a335787585375322f49c5d5fe7b243da7e"
-dependencies = [
- "glob",
- "proc-macro2",
- "quote",
- "syn",
-]
-
 [[package]]
 name = "dirs"
 version = "6.0.0"
@@ -2908,7 +2887,7 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.14.9"
+version = "0.14.10"
 dependencies = [
  "anyhow",
  "argfile",
@@ -3166,7 +3145,7 @@ dependencies = [
 
 [[package]]
 name = "ruff_linter"
-version = "0.14.9"
+version = "0.14.10"
 dependencies = [
  "aho-corasick",
  "anyhow",
@@ -3525,7 +3504,7 @@ dependencies = [
 
 [[package]]
 name = "ruff_wasm"
-version = "0.14.9"
+version = "0.14.10"
 dependencies = [
  "console_error_panic_hook",
  "console_log",
@@ -4513,7 +4492,7 @@ dependencies = [
  "camino",
  "colored 3.0.0",
  "compact_str",
- "dir-test",
+ "datatest-stable",
  "drop_bomb",
  "get-size2",
  "glob",

Cargo.toml

@@ -82,7 +82,6 @@ criterion = { version = "0.7.0", default-features = false }
 crossbeam = { version = "0.8.4" }
 dashmap = { version = "6.0.1" }
 datatest-stable = { version = "0.3.3" }
-dir-test = { version = "0.4.0" }
 dunce = { version = "1.0.5" }
 drop_bomb = { version = "0.1.5" }
 etcetera = { version = "0.11.0" }

README.md

@@ -150,8 +150,8 @@ curl -LsSf https://astral.sh/ruff/install.sh | sh
 powershell -c "irm https://astral.sh/ruff/install.ps1 | iex"
 
 # For a specific version.
-curl -LsSf https://astral.sh/ruff/0.14.9/install.sh | sh
-powershell -c "irm https://astral.sh/ruff/0.14.9/install.ps1 | iex"
+curl -LsSf https://astral.sh/ruff/0.14.10/install.sh | sh
+powershell -c "irm https://astral.sh/ruff/0.14.10/install.ps1 | iex"
 ```
 
 You can also install Ruff via [Homebrew](https://formulae.brew.sh/formula/ruff), [Conda](https://anaconda.org/conda-forge/ruff),
@@ -184,7 +184,7 @@ Ruff can also be used as a [pre-commit](https://pre-commit.com/) hook via [`ruff
 ```yaml
 - repo: https://github.com/astral-sh/ruff-pre-commit
   # Ruff version.
-  rev: v0.14.9
+  rev: v0.14.10
   hooks:
     # Run the linter.
     - id: ruff-check

_typos.toml

@@ -4,6 +4,7 @@ extend-exclude = [
     "crates/ty_vendored/vendor/**/*",
     "**/resources/**/*",
     "**/snapshots/**/*",
+    "crates/ruff_linter/src/rules/flake8_implicit_str_concat/rules/collection_literal.rs",
     # Completion tests tend to have a lot of incomplete
     # words naturally. It's annoying to have to make all
     # of them actually words. So just ignore typos here.

crates/ruff/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff"
-version = "0.14.9"
+version = "0.14.10"
 publish = true
 authors = { workspace = true }
 edition = { workspace = true }

crates/ruff_db/src/system/test.rs

@@ -1,5 +1,6 @@
 use glob::PatternError;
 use ruff_notebook::{Notebook, NotebookError};
+use rustc_hash::FxHashMap;
 use std::panic::RefUnwindSafe;
 use std::sync::{Arc, Mutex};
 
@@ -20,18 +21,44 @@ use super::walk_directory::WalkDirectoryBuilder;
 ///
 /// ## Warning
 /// Don't use this system for production code. It's intended for testing only.
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 pub struct TestSystem {
     inner: Arc<dyn WritableSystem + RefUnwindSafe + Send + Sync>,
+    /// Environment variable overrides. If a key is present here, it takes precedence
+    /// over the inner system's environment variables.
+    env_overrides: Arc<Mutex<FxHashMap<String, Option<String>>>>,
+}
+
+impl Clone for TestSystem {
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
+            env_overrides: self.env_overrides.clone(),
+        }
+    }
 }
 
 impl TestSystem {
     pub fn new(inner: impl WritableSystem + RefUnwindSafe + Send + Sync + 'static) -> Self {
         Self {
             inner: Arc::new(inner),
+            env_overrides: Arc::new(Mutex::new(FxHashMap::default())),
         }
     }
 
+    /// Sets an environment variable override. This takes precedence over the inner system.
+    pub fn set_env_var(&self, name: impl Into<String>, value: impl Into<String>) {
+        self.env_overrides
+            .lock()
+            .unwrap()
+            .insert(name.into(), Some(value.into()));
+    }
+
+    /// Removes an environment variable override, making it appear as not set.
+    pub fn remove_env_var(&self, name: impl Into<String>) {
+        self.env_overrides.lock().unwrap().insert(name.into(), None);
+    }
+
     /// Returns the [`InMemorySystem`].
     ///
     /// ## Panics
@@ -147,6 +174,18 @@ impl System for TestSystem {
         self.system().case_sensitivity()
     }
 
+    fn env_var(&self, name: &str) -> std::result::Result<String, std::env::VarError> {
+        // Check overrides first
+        if let Some(override_value) = self.env_overrides.lock().unwrap().get(name) {
+            return match override_value {
+                Some(value) => Ok(value.clone()),
+                None => Err(std::env::VarError::NotPresent),
+            };
+        }
+        // Fall back to inner system
+        self.system().env_var(name)
+    }
+
     fn dyn_clone(&self) -> Box<dyn System> {
         Box::new(self.clone())
     }
@@ -156,6 +195,7 @@ impl Default for TestSystem {
     fn default() -> Self {
         Self {
             inner: Arc::new(InMemorySystem::default()),
+            env_overrides: Arc::new(Mutex::new(FxHashMap::default())),
         }
     }
 }

crates/ruff_linter/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff_linter"
-version = "0.14.9"
+version = "0.14.10"
 publish = false
 authors = { workspace = true }
 edition = { workspace = true }

crates/ruff_linter/resources/test/fixtures/flake8_implicit_str_concat/ISC004.py

@@ -0,0 +1,66 @@
+facts = (
+    "Lobsters have blue blood.",
+    "The liver is the only human organ that can fully regenerate itself.",
+    "Clarinets are made almost entirely out of wood from the mpingo tree."
+    "In 1971, astronaut Alan Shepard played golf on the moon.",
+)
+
+facts = [
+    "Lobsters have blue blood.",
+    "The liver is the only human organ that can fully regenerate itself.",
+    "Clarinets are made almost entirely out of wood from the mpingo tree."
+    "In 1971, astronaut Alan Shepard played golf on the moon.",
+]
+
+facts = {
+    "Lobsters have blue blood.",
+    "The liver is the only human organ that can fully regenerate itself.",
+    "Clarinets are made almost entirely out of wood from the mpingo tree."
+    "In 1971, astronaut Alan Shepard played golf on the moon.",
+}
+
+facts = {
+    (
+        "Clarinets are made almost entirely out of wood from the mpingo tree."
+        "In 1971, astronaut Alan Shepard played golf on the moon."
+    ),
+}
+
+facts = (
+    "Octopuses have three hearts."
+    # Missing comma here.
+    "Honey never spoils.",
+)
+
+facts = [
+    "Octopuses have three hearts."
+    # Missing comma here.
+    "Honey never spoils.",
+]
+
+facts = {
+    "Octopuses have three hearts."
+    # Missing comma here.
+    "Honey never spoils.",
+}
+
+facts = (
+    (
+        "Clarinets are made almost entirely out of wood from the mpingo tree."
+        "In 1971, astronaut Alan Shepard played golf on the moon."
+    ),
+)
+
+facts = [
+    (
+        "Clarinets are made almost entirely out of wood from the mpingo tree."
+        "In 1971, astronaut Alan Shepard played golf on the moon."
+    ),
+]
+
+facts = (
+    "Lobsters have blue blood.\n"
+    "The liver is the only human organ that can fully regenerate itself.\n"
+    "Clarinets are made almost entirely out of wood from the mpingo tree.\n"
+    "In 1971, astronaut Alan Shepard played golf on the moon.\n"
+)

crates/ruff_linter/resources/test/fixtures/flake8_pytest_style/PT010.py

@@ -9,3 +9,15 @@ def test_ok():
 def test_error():
     with pytest.raises(UnicodeError):
         pass
+
+def test_match_only():
+    with pytest.raises(match="some error message"):
+        pass
+
+def test_check_only():
+    with pytest.raises(check=lambda e: True):
+        pass
+
+def test_match_and_check():
+    with pytest.raises(match="some error message", check=lambda e: True):
+        pass

crates/ruff_linter/resources/test/fixtures/flake8_use_pathlib/full_name.py

@@ -136,4 +136,38 @@ os.chmod("pth1_file", 0o700, None, True, 1, *[1], **{"x": 1}, foo=1)
 os.rename("pth1_file", "pth1_file1", None, None, 1, *[1], **{"x": 1}, foo=1)
 os.replace("pth1_file1", "pth1_file", None, None, 1, *[1], **{"x": 1}, foo=1)
 
-os.path.samefile("pth1_file", "pth1_link", 1, *[1], **{"x": 1}, foo=1)
+os.path.samefile("pth1_file", "pth1_link", 1, *[1], **{"x": 1}, foo=1)
+
+# See: https://github.com/astral-sh/ruff/issues/21794
+import sys
+
+if os.rename("pth1.py", "pth1.py.bak"):
+    print("rename: truthy")
+else:
+    print("rename: falsey")
+
+if os.replace("pth1.py.bak", "pth1.py"):
+    print("replace: truthy")
+else:
+    print("replace: falsey")
+
+try:
+    for _ in os.getcwd():
+        print("getcwd: iterable")
+        break
+except TypeError as e:
+    print("getcwd: not iterable")
+
+try:
+    for _ in os.getcwdb():
+        print("getcwdb: iterable")
+        break
+except TypeError as e:
+    print("getcwdb: not iterable")
+
+try:
+    for _ in os.readlink(sys.executable):
+        print("readlink: iterable")
+        break
+except TypeError as e:
+    print("readlink: not iterable")

crates/ruff_linter/resources/test/fixtures/refurb/FURB101_0.py

@@ -138,5 +138,6 @@ with open("file.txt", encoding="utf-8") as f:
 with open("file.txt", encoding="utf-8") as f:
     contents = process_contents(f.read())
 
-with open("file.txt", encoding="utf-8") as f:
+with open("file1.txt", encoding="utf-8") as f:
     contents: str = process_contents(f.read())
+

crates/ruff_linter/resources/test/fixtures/refurb/FURB101_1.py

@@ -0,0 +1,8 @@
+
+from pathlib import Path
+
+with Path("file.txt").open() as f:
+    contents = f.read()
+
+with Path("file.txt").open("r") as f:
+    contents = f.read()

crates/ruff_linter/resources/test/fixtures/refurb/FURB103_1.py

@@ -0,0 +1,26 @@
+from pathlib import Path
+
+with Path("file.txt").open("w") as f:
+    f.write("test")
+
+with Path("file.txt").open("wb") as f:
+    f.write(b"test")
+
+with Path("file.txt").open(mode="w") as f:
+    f.write("test")
+
+with Path("file.txt").open("w", encoding="utf8") as f:
+    f.write("test")
+
+with Path("file.txt").open("w", errors="ignore") as f:
+    f.write("test")
+
+with Path(foo()).open("w") as f:
+    f.write("test")
+
+p = Path("file.txt")
+with p.open("w") as f:
+    f.write("test")
+
+with Path("foo", "bar", "baz").open("w") as f:
+    f.write("test")

crates/ruff_linter/resources/test/fixtures/ruff/suppressions.py

@@ -86,3 +86,26 @@ def f():
     # Multiple codes but none are used
     # ruff: disable[E741, F401, F841]
     print("hello")
+
+
+def f():
+    # Unknown rule codes
+    # ruff: disable[YF829]
+    # ruff: disable[F841, RQW320]
+    value = 0
+    # ruff: enable[F841, RQW320]
+    # ruff: enable[YF829]
+
+
+def f():
+    # External rule codes should be ignored
+    # ruff: disable[TK421]
+    print("hello")
+    # ruff: enable[TK421]
+
+
+def f():
+    # Empty or missing rule codes
+    # ruff: disable
+    # ruff: disable[]
+    print("hello")

crates/ruff_linter/resources/test/fixtures/semantic_errors/annotated_global.py

@@ -0,0 +1,38 @@
+a: int = 1
+def f1():
+    global a
+    a: str = "foo"  # error
+
+b: int = 1
+def outer():
+    def inner():
+        global b
+        b: str = "nested"  # error
+
+c: int = 1
+def f2():
+    global c
+    c: list[str] = []  # error
+
+d: int = 1
+def f3():
+    global d
+    d: str  # error
+
+e: int = 1
+def f4():
+    e: str = "happy"  # okay
+
+global f
+f: int = 1  # okay
+
+g: int = 1
+global g  # error
+
+class C:
+    x: str
+    global x  # error
+
+class D:
+    global x  # error
+    x: str

crates/ruff_linter/src/checkers/ast/analyze/expression.rs

@@ -214,6 +214,13 @@ pub(crate) fn expression(expr: &Expr, checker: &Checker) {
             range: _,
             node_index: _,
         }) => {
+            if checker.is_rule_enabled(Rule::ImplicitStringConcatenationInCollectionLiteral) {
+                flake8_implicit_str_concat::rules::implicit_string_concatenation_in_collection_literal(
+                    checker,
+                    expr,
+                    elts,
+                );
+            }
             if ctx.is_store() {
                 let check_too_many_expressions =
                     checker.is_rule_enabled(Rule::ExpressionsInStarAssignment);
@@ -1329,6 +1336,13 @@ pub(crate) fn expression(expr: &Expr, checker: &Checker) {
             }
         }
         Expr::Set(set) => {
+            if checker.is_rule_enabled(Rule::ImplicitStringConcatenationInCollectionLiteral) {
+                flake8_implicit_str_concat::rules::implicit_string_concatenation_in_collection_literal(
+                    checker,
+                    expr,
+                    &set.elts,
+                );
+            }
             if checker.is_rule_enabled(Rule::DuplicateValue) {
                 flake8_bugbear::rules::duplicate_value(checker, set);
             }

crates/ruff_linter/src/codes.rs

@@ -454,6 +454,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Flake8ImplicitStrConcat, "001") => rules::flake8_implicit_str_concat::rules::SingleLineImplicitStringConcatenation,
         (Flake8ImplicitStrConcat, "002") => rules::flake8_implicit_str_concat::rules::MultiLineImplicitStringConcatenation,
         (Flake8ImplicitStrConcat, "003") => rules::flake8_implicit_str_concat::rules::ExplicitStringConcatenation,
+        (Flake8ImplicitStrConcat, "004") => rules::flake8_implicit_str_concat::rules::ImplicitStringConcatenationInCollectionLiteral,
 
         // flake8-print
         (Flake8Print, "1") => rules::flake8_print::rules::Print,
@@ -1063,6 +1064,8 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Ruff, "100") => rules::ruff::rules::UnusedNOQA,
         (Ruff, "101") => rules::ruff::rules::RedirectedNOQA,
         (Ruff, "102") => rules::ruff::rules::InvalidRuleCode,
+        (Ruff, "103") => rules::ruff::rules::InvalidSuppressionComment,
+        (Ruff, "104") => rules::ruff::rules::UnmatchedSuppressionComment,
 
         (Ruff, "200") => rules::ruff::rules::InvalidPyprojectToml,
         #[cfg(any(feature = "test-rules", test))]

crates/ruff_linter/src/linter.rs

@@ -1001,6 +1001,7 @@ mod tests {
     #[test_case(Path::new("write_to_debug.py"), PythonVersion::PY310)]
     #[test_case(Path::new("invalid_expression.py"), PythonVersion::PY312)]
     #[test_case(Path::new("global_parameter.py"), PythonVersion::PY310)]
+    #[test_case(Path::new("annotated_global.py"), PythonVersion::PY314)]
     fn test_semantic_errors(path: &Path, python_version: PythonVersion) -> Result<()> {
         let snapshot = format!(
             "semantic_syntax_error_{}_{}",

crates/ruff_linter/src/rules/eradicate/detection.rs

@@ -22,6 +22,7 @@ static ALLOWLIST_REGEX: LazyLock<Regex> = LazyLock::new(|| {
             # Case-sensitive
             pyright
         |   pyrefly
+        |   ruff\s*:\s*(disable|enable)
         |   mypy:
         |   type:\s*ignore
         |   SPDX-License-Identifier:
@@ -148,6 +149,8 @@ mod tests {
         assert!(!comment_contains_code("# 123", &[]));
         assert!(!comment_contains_code("# 123.1", &[]));
         assert!(!comment_contains_code("# 1, 2, 3", &[]));
+        assert!(!comment_contains_code("# ruff: disable[E501]", &[]));
+        assert!(!comment_contains_code("#ruff:enable[E501, F84]", &[]));
         assert!(!comment_contains_code(
             "# pylint: disable=redefined-outer-name",
             &[]

crates/ruff_linter/src/rules/flake8_async/rules/blocking_open_call.rs

@@ -70,7 +70,7 @@ fn is_open_call(func: &Expr, semantic: &SemanticModel) -> bool {
 }
 
 /// Returns `true` if an expression resolves to a call to `pathlib.Path.open`.
-fn is_open_call_from_pathlib(func: &Expr, semantic: &SemanticModel) -> bool {
+pub(crate) fn is_open_call_from_pathlib(func: &Expr, semantic: &SemanticModel) -> bool {
     let Expr::Attribute(ast::ExprAttribute { attr, value, .. }) = func else {
         return false;
     };

crates/ruff_linter/src/rules/flake8_async/rules/mod.rs

@@ -18,7 +18,7 @@ mod async_zero_sleep;
 mod blocking_http_call;
 mod blocking_http_call_httpx;
 mod blocking_input;
-mod blocking_open_call;
+pub(crate) mod blocking_open_call;
 mod blocking_path_methods;
 mod blocking_process_invocation;
 mod blocking_sleep;

crates/ruff_linter/src/rules/flake8_bandit/rules/unsafe_markup_use.rs

@@ -12,7 +12,7 @@ use crate::{checkers::ast::Checker, settings::LinterSettings};
 /// Checks for non-literal strings being passed to [`markupsafe.Markup`][markupsafe-markup].
 ///
 /// ## Why is this bad?
-/// [`markupsafe.Markup`] does not perform any escaping, so passing dynamic
+/// [`markupsafe.Markup`][markupsafe-markup] does not perform any escaping, so passing dynamic
 /// content, like f-strings, variables or interpolated strings will potentially
 /// lead to XSS vulnerabilities.
 ///

crates/ruff_linter/src/rules/flake8_implicit_str_concat/mod.rs

@@ -32,6 +32,10 @@ mod tests {
         Path::new("ISC_syntax_error_2.py")
     )]
     #[test_case(Rule::ExplicitStringConcatenation, Path::new("ISC.py"))]
+    #[test_case(
+        Rule::ImplicitStringConcatenationInCollectionLiteral,
+        Path::new("ISC004.py")
+    )]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());
         let diagnostics = test_path(

crates/ruff_linter/src/rules/flake8_implicit_str_concat/rules/collection_literal.rs

@@ -0,0 +1,103 @@
+use ruff_macros::{ViolationMetadata, derive_message_formats};
+use ruff_python_ast::token::parenthesized_range;
+use ruff_python_ast::{Expr, StringLike};
+use ruff_text_size::Ranged;
+
+use crate::checkers::ast::Checker;
+use crate::{Edit, Fix, FixAvailability, Violation};
+
+/// ## What it does
+/// Checks for implicitly concatenated strings inside list, tuple, and set literals.
+///
+/// ## Why is this bad?
+/// In collection literals, implicit string concatenation is often the result of
+/// a missing comma between elements, which can silently merge items together.
+///
+/// ## Example
+/// ```python
+/// facts = (
+///     "Lobsters have blue blood.",
+///     "The liver is the only human organ that can fully regenerate itself.",
+///     "Clarinets are made almost entirely out of wood from the mpingo tree."
+///     "In 1971, astronaut Alan Shepard played golf on the moon.",
+/// )
+/// ```
+///
+/// Instead, you likely intended:
+/// ```python
+/// facts = (
+///     "Lobsters have blue blood.",
+///     "The liver is the only human organ that can fully regenerate itself.",
+///     "Clarinets are made almost entirely out of wood from the mpingo tree.",
+///     "In 1971, astronaut Alan Shepard played golf on the moon.",
+/// )
+/// ```
+///
+/// If the concatenation is intentional, wrap it in parentheses to make it
+/// explicit:
+/// ```python
+/// facts = (
+///     "Lobsters have blue blood.",
+///     "The liver is the only human organ that can fully regenerate itself.",
+///     (
+///         "Clarinets are made almost entirely out of wood from the mpingo tree."
+///         "In 1971, astronaut Alan Shepard played golf on the moon."
+///     ),
+/// )
+/// ```
+///
+/// ## Fix safety
+/// The fix is safe in that it does not change the semantics of your code.
+/// However, the issue is that you may often want to change semantics
+/// by adding a missing comma.
+#[derive(ViolationMetadata)]
+#[violation_metadata(preview_since = "0.14.10")]
+pub(crate) struct ImplicitStringConcatenationInCollectionLiteral;
+
+impl Violation for ImplicitStringConcatenationInCollectionLiteral {
+    const FIX_AVAILABILITY: FixAvailability = FixAvailability::Always;
+
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        "Unparenthesized implicit string concatenation in collection".to_string()
+    }
+
+    fn fix_title(&self) -> Option<String> {
+        Some("Wrap implicitly concatenated strings in parentheses".to_string())
+    }
+}
+
+/// ISC004
+pub(crate) fn implicit_string_concatenation_in_collection_literal(
+    checker: &Checker,
+    expr: &Expr,
+    elements: &[Expr],
+) {
+    for element in elements {
+        let Ok(string_like) = StringLike::try_from(element) else {
+            continue;
+        };
+        if !string_like.is_implicit_concatenated() {
+            continue;
+        }
+        if parenthesized_range(
+            string_like.as_expression_ref(),
+            expr.into(),
+            checker.tokens(),
+        )
+        .is_some()
+        {
+            continue;
+        }
+
+        let mut diagnostic = checker.report_diagnostic(
+            ImplicitStringConcatenationInCollectionLiteral,
+            string_like.range(),
+        );
+        diagnostic.help("Did you forget a comma?");
+        diagnostic.set_fix(Fix::unsafe_edits(
+            Edit::insertion("(".to_string(), string_like.range().start()),
+            [Edit::insertion(")".to_string(), string_like.range().end())],
+        ));
+    }
+}

crates/ruff_linter/src/rules/flake8_implicit_str_concat/rules/mod.rs

@@ -1,5 +1,7 @@
+pub(crate) use collection_literal::*;
 pub(crate) use explicit::*;
 pub(crate) use implicit::*;
 
+mod collection_literal;
 mod explicit;
 mod implicit;

crates/ruff_linter/src/rules/flake8_implicit_str_concat/snapshots/ruff_linter__rules__flake8_implicit_str_concat__tests__ISC004_ISC004.py.snap

@@ -0,0 +1,149 @@
+---
+source: crates/ruff_linter/src/rules/flake8_implicit_str_concat/mod.rs
+---
+ISC004 [*] Unparenthesized implicit string concatenation in collection
+ --> ISC004.py:4:5
+  |
+2 |       "Lobsters have blue blood.",
+3 |       "The liver is the only human organ that can fully regenerate itself.",
+4 | /     "Clarinets are made almost entirely out of wood from the mpingo tree."
+5 | |     "In 1971, astronaut Alan Shepard played golf on the moon.",
+  | |______________________________________________________________^
+6 |   )
+  |
+help: Wrap implicitly concatenated strings in parentheses
+help: Did you forget a comma?
+1 | facts = (
+2 |     "Lobsters have blue blood.",
+3 |     "The liver is the only human organ that can fully regenerate itself.",
+  -     "Clarinets are made almost entirely out of wood from the mpingo tree."
+  -     "In 1971, astronaut Alan Shepard played golf on the moon.",
+4 +     ("Clarinets are made almost entirely out of wood from the mpingo tree."
+5 +     "In 1971, astronaut Alan Shepard played golf on the moon."),
+6 | )
+7 | 
+8 | facts = [
+note: This is an unsafe fix and may change runtime behavior
+
+ISC004 [*] Unparenthesized implicit string concatenation in collection
+  --> ISC004.py:11:5
+   |
+ 9 |       "Lobsters have blue blood.",
+10 |       "The liver is the only human organ that can fully regenerate itself.",
+11 | /     "Clarinets are made almost entirely out of wood from the mpingo tree."
+12 | |     "In 1971, astronaut Alan Shepard played golf on the moon.",
+   | |______________________________________________________________^
+13 |   ]
+   |
+help: Wrap implicitly concatenated strings in parentheses
+help: Did you forget a comma?
+8  | facts = [
+9  |     "Lobsters have blue blood.",
+10 |     "The liver is the only human organ that can fully regenerate itself.",
+   -     "Clarinets are made almost entirely out of wood from the mpingo tree."
+   -     "In 1971, astronaut Alan Shepard played golf on the moon.",
+11 +     ("Clarinets are made almost entirely out of wood from the mpingo tree."
+12 +     "In 1971, astronaut Alan Shepard played golf on the moon."),
+13 | ]
+14 | 
+15 | facts = {
+note: This is an unsafe fix and may change runtime behavior
+
+ISC004 [*] Unparenthesized implicit string concatenation in collection
+  --> ISC004.py:18:5
+   |
+16 |       "Lobsters have blue blood.",
+17 |       "The liver is the only human organ that can fully regenerate itself.",
+18 | /     "Clarinets are made almost entirely out of wood from the mpingo tree."
+19 | |     "In 1971, astronaut Alan Shepard played golf on the moon.",
+   | |______________________________________________________________^
+20 |   }
+   |
+help: Wrap implicitly concatenated strings in parentheses
+help: Did you forget a comma?
+15 | facts = {
+16 |     "Lobsters have blue blood.",
+17 |     "The liver is the only human organ that can fully regenerate itself.",
+   -     "Clarinets are made almost entirely out of wood from the mpingo tree."
+   -     "In 1971, astronaut Alan Shepard played golf on the moon.",
+18 +     ("Clarinets are made almost entirely out of wood from the mpingo tree."
+19 +     "In 1971, astronaut Alan Shepard played golf on the moon."),
+20 | }
+21 | 
+22 | facts = {
+note: This is an unsafe fix and may change runtime behavior
+
+ISC004 [*] Unparenthesized implicit string concatenation in collection
+  --> ISC004.py:30:5
+   |
+29 |   facts = (
+30 | /     "Octopuses have three hearts."
+31 | |     # Missing comma here.
+32 | |     "Honey never spoils.",
+   | |_________________________^
+33 |   )
+   |
+help: Wrap implicitly concatenated strings in parentheses
+help: Did you forget a comma?
+27 | }
+28 | 
+29 | facts = (
+   -     "Octopuses have three hearts."
+30 +     ("Octopuses have three hearts."
+31 |     # Missing comma here.
+   -     "Honey never spoils.",
+32 +     "Honey never spoils."),
+33 | )
+34 | 
+35 | facts = [
+note: This is an unsafe fix and may change runtime behavior
+
+ISC004 [*] Unparenthesized implicit string concatenation in collection
+  --> ISC004.py:36:5
+   |
+35 |   facts = [
+36 | /     "Octopuses have three hearts."
+37 | |     # Missing comma here.
+38 | |     "Honey never spoils.",
+   | |_________________________^
+39 |   ]
+   |
+help: Wrap implicitly concatenated strings in parentheses
+help: Did you forget a comma?
+33 | )
+34 | 
+35 | facts = [
+   -     "Octopuses have three hearts."
+36 +     ("Octopuses have three hearts."
+37 |     # Missing comma here.
+   -     "Honey never spoils.",
+38 +     "Honey never spoils."),
+39 | ]
+40 | 
+41 | facts = {
+note: This is an unsafe fix and may change runtime behavior
+
+ISC004 [*] Unparenthesized implicit string concatenation in collection
+  --> ISC004.py:42:5
+   |
+41 |   facts = {
+42 | /     "Octopuses have three hearts."
+43 | |     # Missing comma here.
+44 | |     "Honey never spoils.",
+   | |_________________________^
+45 |   }
+   |
+help: Wrap implicitly concatenated strings in parentheses
+help: Did you forget a comma?
+39 | ]
+40 | 
+41 | facts = {
+   -     "Octopuses have three hearts."
+42 +     ("Octopuses have three hearts."
+43 |     # Missing comma here.
+   -     "Honey never spoils.",
+44 +     "Honey never spoils."),
+45 | }
+46 | 
+47 | facts = (
+note: This is an unsafe fix and may change runtime behavior

crates/ruff_linter/src/rules/flake8_pytest_style/rules/raises.rs

@@ -125,6 +125,9 @@ impl Violation for PytestRaisesTooBroad {
 /// ## Why is this bad?
 /// `pytest.raises` expects to receive an expected exception as its first
 /// argument. If omitted, the `pytest.raises` call will fail at runtime.
+/// The rule will also accept calls without an expected exception but with
+/// `match` and/or `check` keyword arguments, which are also valid after
+/// pytest version 8.4.0.
 ///
 /// ## Example
 /// ```python
@@ -181,6 +184,8 @@ pub(crate) fn raises_call(checker: &Checker, call: &ast::ExprCall) {
                 .arguments
                 .find_argument("expected_exception", 0)
                 .is_none()
+                && call.arguments.find_keyword("match").is_none()
+                && call.arguments.find_keyword("check").is_none()
             {
                 checker.report_diagnostic(PytestRaisesWithoutException, call.func.range());
             }

crates/ruff_linter/src/rules/flake8_use_pathlib/helpers.rs

@@ -210,6 +210,7 @@ pub(crate) fn is_argument_non_default(arguments: &Arguments, name: &str, positio
 
 /// Returns `true` if the given call is a top-level expression in its statement.
 /// This means the call's return value is not used, so return type changes don't matter.
-pub(crate) fn is_top_level_expression_call(checker: &Checker) -> bool {
+pub(crate) fn is_top_level_expression_in_statement(checker: &Checker) -> bool {
     checker.semantic().current_expression_parent().is_none()
+        && checker.semantic().current_statement().is_expr_stmt()
 }

crates/ruff_linter/src/rules/flake8_use_pathlib/rules/os_getcwd.rs

@@ -6,7 +6,7 @@ use ruff_text_size::Ranged;
 use crate::checkers::ast::Checker;
 use crate::importer::ImportRequest;
 use crate::preview::is_fix_os_getcwd_enabled;
-use crate::rules::flake8_use_pathlib::helpers::is_top_level_expression_call;
+use crate::rules::flake8_use_pathlib::helpers::is_top_level_expression_in_statement;
 use crate::{FixAvailability, Violation};
 
 /// ## What it does
@@ -89,7 +89,7 @@ pub(crate) fn os_getcwd(checker: &Checker, call: &ExprCall, segments: &[&str]) {
 
             // Unsafe when the fix would delete comments or change a used return value
             let applicability = if checker.comment_ranges().intersects(range)
-                || !is_top_level_expression_call(checker)
+                || !is_top_level_expression_in_statement(checker)
             {
                 Applicability::Unsafe
             } else {

crates/ruff_linter/src/rules/flake8_use_pathlib/rules/os_readlink.rs

@@ -6,7 +6,7 @@ use crate::checkers::ast::Checker;
 use crate::preview::is_fix_os_readlink_enabled;
 use crate::rules::flake8_use_pathlib::helpers::{
     check_os_pathlib_single_arg_calls, is_keyword_only_argument_non_default,
-    is_top_level_expression_call,
+    is_top_level_expression_in_statement,
 };
 use crate::{FixAvailability, Violation};
 
@@ -86,7 +86,7 @@ pub(crate) fn os_readlink(checker: &Checker, call: &ExprCall, segments: &[&str])
         return;
     }
 
-    let applicability = if !is_top_level_expression_call(checker) {
+    let applicability = if !is_top_level_expression_in_statement(checker) {
         // Unsafe because the return type changes (str/bytes -> Path)
         Applicability::Unsafe
     } else {

crates/ruff_linter/src/rules/flake8_use_pathlib/rules/os_rename.rs

@@ -6,7 +6,7 @@ use crate::checkers::ast::Checker;
 use crate::preview::is_fix_os_rename_enabled;
 use crate::rules::flake8_use_pathlib::helpers::{
     check_os_pathlib_two_arg_calls, has_unknown_keywords_or_starred_expr,
-    is_keyword_only_argument_non_default, is_top_level_expression_call,
+    is_keyword_only_argument_non_default, is_top_level_expression_in_statement,
 };
 use crate::{FixAvailability, Violation};
 
@@ -92,7 +92,7 @@ pub(crate) fn os_rename(checker: &Checker, call: &ExprCall, segments: &[&str]) {
         );
 
     // Unsafe when the fix would delete comments or change a used return value
-    let applicability = if !is_top_level_expression_call(checker) {
+    let applicability = if !is_top_level_expression_in_statement(checker) {
         // Unsafe because the return type changes (None -> Path)
         Applicability::Unsafe
     } else {

crates/ruff_linter/src/rules/flake8_use_pathlib/rules/os_replace.rs

@@ -6,7 +6,7 @@ use crate::checkers::ast::Checker;
 use crate::preview::is_fix_os_replace_enabled;
 use crate::rules::flake8_use_pathlib::helpers::{
     check_os_pathlib_two_arg_calls, has_unknown_keywords_or_starred_expr,
-    is_keyword_only_argument_non_default, is_top_level_expression_call,
+    is_keyword_only_argument_non_default, is_top_level_expression_in_statement,
 };
 use crate::{FixAvailability, Violation};
 
@@ -95,7 +95,7 @@ pub(crate) fn os_replace(checker: &Checker, call: &ExprCall, segments: &[&str])
         );
 
     // Unsafe when the fix would delete comments or change a used return value
-    let applicability = if !is_top_level_expression_call(checker) {
+    let applicability = if !is_top_level_expression_in_statement(checker) {
         // Unsafe because the return type changes (None -> Path)
         Applicability::Unsafe
     } else {

crates/ruff_linter/src/rules/flake8_use_pathlib/snapshots/ruff_linter__rules__flake8_use_pathlib__tests__full_name.py.snap

@@ -567,5 +567,64 @@ PTH121 `os.path.samefile()` should be replaced by `Path.samefile()`
 138 |
 139 | os.path.samefile("pth1_file", "pth1_link", 1, *[1], **{"x": 1}, foo=1)
     | ^^^^^^^^^^^^^^^^
+140 |
+141 | # See: https://github.com/astral-sh/ruff/issues/21794
     |
 help: Replace with `Path(...).samefile()`
+
+PTH104 `os.rename()` should be replaced by `Path.rename()`
+   --> full_name.py:144:4
+    |
+142 | import sys
+143 |
+144 | if os.rename("pth1.py", "pth1.py.bak"):
+    |    ^^^^^^^^^
+145 |     print("rename: truthy")
+146 | else:
+    |
+help: Replace with `Path(...).rename(...)`
+
+PTH105 `os.replace()` should be replaced by `Path.replace()`
+   --> full_name.py:149:4
+    |
+147 |     print("rename: falsey")
+148 |
+149 | if os.replace("pth1.py.bak", "pth1.py"):
+    |    ^^^^^^^^^^
+150 |     print("replace: truthy")
+151 | else:
+    |
+help: Replace with `Path(...).replace(...)`
+
+PTH109 `os.getcwd()` should be replaced by `Path.cwd()`
+   --> full_name.py:155:14
+    |
+154 | try:
+155 |     for _ in os.getcwd():
+    |              ^^^^^^^^^
+156 |         print("getcwd: iterable")
+157 |         break
+    |
+help: Replace with `Path.cwd()`
+
+PTH109 `os.getcwd()` should be replaced by `Path.cwd()`
+   --> full_name.py:162:14
+    |
+161 | try:
+162 |     for _ in os.getcwdb():
+    |              ^^^^^^^^^^
+163 |         print("getcwdb: iterable")
+164 |         break
+    |
+help: Replace with `Path.cwd()`
+
+PTH115 `os.readlink()` should be replaced by `Path.readlink()`
+   --> full_name.py:169:14
+    |
+168 | try:
+169 |     for _ in os.readlink(sys.executable):
+    |              ^^^^^^^^^^^
+170 |         print("readlink: iterable")
+171 |         break
+    |
+help: Replace with `Path(...).readlink()`

crates/ruff_linter/src/rules/flake8_use_pathlib/snapshots/ruff_linter__rules__flake8_use_pathlib__tests__preview_full_name.py.snap

@@ -1037,5 +1037,142 @@ PTH121 `os.path.samefile()` should be replaced by `Path.samefile()`
 138 |
 139 | os.path.samefile("pth1_file", "pth1_link", 1, *[1], **{"x": 1}, foo=1)
     | ^^^^^^^^^^^^^^^^
+140 |
+141 | # See: https://github.com/astral-sh/ruff/issues/21794
     |
 help: Replace with `Path(...).samefile()`
+
+PTH104 [*] `os.rename()` should be replaced by `Path.rename()`
+   --> full_name.py:144:4
+    |
+142 | import sys
+143 |
+144 | if os.rename("pth1.py", "pth1.py.bak"):
+    |    ^^^^^^^^^
+145 |     print("rename: truthy")
+146 | else:
+    |
+help: Replace with `Path(...).rename(...)`
+140 | 
+141 | # See: https://github.com/astral-sh/ruff/issues/21794
+142 | import sys
+143 + import pathlib
+144 | 
+    - if os.rename("pth1.py", "pth1.py.bak"):
+145 + if pathlib.Path("pth1.py").rename("pth1.py.bak"):
+146 |     print("rename: truthy")
+147 | else:
+148 |     print("rename: falsey")
+note: This is an unsafe fix and may change runtime behavior
+
+PTH105 [*] `os.replace()` should be replaced by `Path.replace()`
+   --> full_name.py:149:4
+    |
+147 |     print("rename: falsey")
+148 |
+149 | if os.replace("pth1.py.bak", "pth1.py"):
+    |    ^^^^^^^^^^
+150 |     print("replace: truthy")
+151 | else:
+    |
+help: Replace with `Path(...).replace(...)`
+140 | 
+141 | # See: https://github.com/astral-sh/ruff/issues/21794
+142 | import sys
+143 + import pathlib
+144 | 
+145 | if os.rename("pth1.py", "pth1.py.bak"):
+146 |     print("rename: truthy")
+147 | else:
+148 |     print("rename: falsey")
+149 | 
+    - if os.replace("pth1.py.bak", "pth1.py"):
+150 + if pathlib.Path("pth1.py.bak").replace("pth1.py"):
+151 |     print("replace: truthy")
+152 | else:
+153 |     print("replace: falsey")
+note: This is an unsafe fix and may change runtime behavior
+
+PTH109 [*] `os.getcwd()` should be replaced by `Path.cwd()`
+   --> full_name.py:155:14
+    |
+154 | try:
+155 |     for _ in os.getcwd():
+    |              ^^^^^^^^^
+156 |         print("getcwd: iterable")
+157 |         break
+    |
+help: Replace with `Path.cwd()`
+140 | 
+141 | # See: https://github.com/astral-sh/ruff/issues/21794
+142 | import sys
+143 + import pathlib
+144 | 
+145 | if os.rename("pth1.py", "pth1.py.bak"):
+146 |     print("rename: truthy")
+--------------------------------------------------------------------------------
+153 |     print("replace: falsey")
+154 | 
+155 | try:
+    -     for _ in os.getcwd():
+156 +     for _ in pathlib.Path.cwd():
+157 |         print("getcwd: iterable")
+158 |         break
+159 | except TypeError as e:
+note: This is an unsafe fix and may change runtime behavior
+
+PTH109 [*] `os.getcwd()` should be replaced by `Path.cwd()`
+   --> full_name.py:162:14
+    |
+161 | try:
+162 |     for _ in os.getcwdb():
+    |              ^^^^^^^^^^
+163 |         print("getcwdb: iterable")
+164 |         break
+    |
+help: Replace with `Path.cwd()`
+140 | 
+141 | # See: https://github.com/astral-sh/ruff/issues/21794
+142 | import sys
+143 + import pathlib
+144 | 
+145 | if os.rename("pth1.py", "pth1.py.bak"):
+146 |     print("rename: truthy")
+--------------------------------------------------------------------------------
+160 |     print("getcwd: not iterable")
+161 | 
+162 | try:
+    -     for _ in os.getcwdb():
+163 +     for _ in pathlib.Path.cwd():
+164 |         print("getcwdb: iterable")
+165 |         break
+166 | except TypeError as e:
+note: This is an unsafe fix and may change runtime behavior
+
+PTH115 [*] `os.readlink()` should be replaced by `Path.readlink()`
+   --> full_name.py:169:14
+    |
+168 | try:
+169 |     for _ in os.readlink(sys.executable):
+    |              ^^^^^^^^^^^
+170 |         print("readlink: iterable")
+171 |         break
+    |
+help: Replace with `Path(...).readlink()`
+140 | 
+141 | # See: https://github.com/astral-sh/ruff/issues/21794
+142 | import sys
+143 + import pathlib
+144 | 
+145 | if os.rename("pth1.py", "pth1.py.bak"):
+146 |     print("rename: truthy")
+--------------------------------------------------------------------------------
+167 |     print("getcwdb: not iterable")
+168 | 
+169 | try:
+    -     for _ in os.readlink(sys.executable):
+170 +     for _ in pathlib.Path(sys.executable).readlink():
+171 |         print("readlink: iterable")
+172 |         break
+173 | except TypeError as e:
+note: This is an unsafe fix and may change runtime behavior

crates/ruff_linter/src/rules/refurb/helpers.rs

@@ -3,10 +3,11 @@ use std::borrow::Cow;
 use ruff_python_ast::PythonVersion;
 use ruff_python_ast::{self as ast, Expr, name::Name, token::parenthesized_range};
 use ruff_python_codegen::Generator;
-use ruff_python_semantic::{BindingId, ResolvedReference, SemanticModel};
+use ruff_python_semantic::{ResolvedReference, SemanticModel};
 use ruff_text_size::{Ranged, TextRange};
 
 use crate::checkers::ast::Checker;
+use crate::rules::flake8_async::rules::blocking_open_call::is_open_call_from_pathlib;
 use crate::{Applicability, Edit, Fix};
 
 /// Format a code snippet to call `name.method()`.
@@ -119,14 +120,13 @@ impl OpenMode {
 pub(super) struct FileOpen<'a> {
     /// With item where the open happens, we use it for the reporting range.
     pub(super) item: &'a ast::WithItem,
-    /// Filename expression used as the first argument in `open`, we use it in the diagnostic message.
-    pub(super) filename: &'a Expr,
     /// The file open mode.
     pub(super) mode: OpenMode,
     /// The file open keywords.
     pub(super) keywords: Vec<&'a ast::Keyword>,
     /// We only check `open` operations whose file handles are used exactly once.
     pub(super) reference: &'a ResolvedReference,
+    pub(super) argument: OpenArgument<'a>,
 }
 
 impl FileOpen<'_> {
@@ -137,6 +137,45 @@ impl FileOpen<'_> {
     }
 }
 
+#[derive(Debug, Clone, Copy)]
+pub(super) enum OpenArgument<'a> {
+    /// The filename argument to `open`, e.g. "foo.txt" in:
+    ///
+    /// ```py
+    /// f = open("foo.txt")
+    /// ```
+    Builtin { filename: &'a Expr },
+    /// The `Path` receiver of a `pathlib.Path.open` call, e.g. the `p` in the
+    /// context manager in:
+    ///
+    /// ```py
+    /// p = Path("foo.txt")
+    /// with p.open() as f: ...
+    /// ```
+    ///
+    /// or `Path("foo.txt")` in
+    ///
+    /// ```py
+    /// with Path("foo.txt").open() as f: ...
+    /// ```
+    Pathlib { path: &'a Expr },
+}
+
+impl OpenArgument<'_> {
+    pub(super) fn display<'src>(&self, source: &'src str) -> &'src str {
+        &source[self.range()]
+    }
+}
+
+impl Ranged for OpenArgument<'_> {
+    fn range(&self) -> TextRange {
+        match self {
+            OpenArgument::Builtin { filename } => filename.range(),
+            OpenArgument::Pathlib { path } => path.range(),
+        }
+    }
+}
+
 /// Find and return all `open` operations in the given `with` statement.
 pub(super) fn find_file_opens<'a>(
     with: &'a ast::StmtWith,
@@ -146,10 +185,65 @@ pub(super) fn find_file_opens<'a>(
 ) -> Vec<FileOpen<'a>> {
     with.items
         .iter()
-        .filter_map(|item| find_file_open(item, with, semantic, read_mode, python_version))
+        .filter_map(|item| {
+            find_file_open(item, with, semantic, read_mode, python_version)
+                .or_else(|| find_path_open(item, with, semantic, read_mode, python_version))
+        })
         .collect()
 }
 
+fn resolve_file_open<'a>(
+    item: &'a ast::WithItem,
+    with: &'a ast::StmtWith,
+    semantic: &'a SemanticModel<'a>,
+    read_mode: bool,
+    mode: OpenMode,
+    keywords: Vec<&'a ast::Keyword>,
+    argument: OpenArgument<'a>,
+) -> Option<FileOpen<'a>> {
+    match mode {
+        OpenMode::ReadText | OpenMode::ReadBytes => {
+            if !read_mode {
+                return None;
+            }
+        }
+        OpenMode::WriteText | OpenMode::WriteBytes => {
+            if read_mode {
+                return None;
+            }
+        }
+    }
+
+    if matches!(mode, OpenMode::ReadBytes | OpenMode::WriteBytes) && !keywords.is_empty() {
+        return None;
+    }
+    let var = item.optional_vars.as_deref()?.as_name_expr()?;
+    let scope = semantic.current_scope();
+
+    let binding = scope.get_all(var.id.as_str()).find_map(|id| {
+        let b = semantic.binding(id);
+        (b.range() == var.range()).then_some(b)
+    })?;
+    let references: Vec<&ResolvedReference> = binding
+        .references
+        .iter()
+        .map(|id| semantic.reference(*id))
+        .filter(|reference| with.range().contains_range(reference.range()))
+        .collect();
+
+    let [reference] = references.as_slice() else {
+        return None;
+    };
+
+    Some(FileOpen {
+        item,
+        mode,
+        keywords,
+        reference,
+        argument,
+    })
+}
+
 /// Find `open` operation in the given `with` item.
 fn find_file_open<'a>(
     item: &'a ast::WithItem,
@@ -165,8 +259,6 @@ fn find_file_open<'a>(
         ..
     } = item.context_expr.as_call_expr()?;
 
-    let var = item.optional_vars.as_deref()?.as_name_expr()?;
-
     // Ignore calls with `*args` and `**kwargs`. In the exact case of `open(*filename, mode="w")`,
     // it could be a match; but in all other cases, the call _could_ contain unsupported keyword
     // arguments, like `buffering`.
@@ -187,58 +279,57 @@ fn find_file_open<'a>(
     let (keywords, kw_mode) = match_open_keywords(keywords, read_mode, python_version)?;
 
     let mode = kw_mode.unwrap_or(pos_mode);
-
-    match mode {
-        OpenMode::ReadText | OpenMode::ReadBytes => {
-            if !read_mode {
-                return None;
-            }
-        }
-        OpenMode::WriteText | OpenMode::WriteBytes => {
-            if read_mode {
-                return None;
-            }
-        }
-    }
-
-    // Path.read_bytes and Path.write_bytes do not support any kwargs.
-    if matches!(mode, OpenMode::ReadBytes | OpenMode::WriteBytes) && !keywords.is_empty() {
-        return None;
-    }
-
-    // Now we need to find what is this variable bound to...
-    let scope = semantic.current_scope();
-    let bindings: Vec<BindingId> = scope.get_all(var.id.as_str()).collect();
-
-    let binding = bindings
-        .iter()
-        .map(|id| semantic.binding(*id))
-        // We might have many bindings with the same name, but we only care
-        // for the one we are looking at right now.
-        .find(|binding| binding.range() == var.range())?;
-
-    // Since many references can share the same binding, we can limit our attention span
-    // exclusively to the body of the current `with` statement.
-    let references: Vec<&ResolvedReference> = binding
-        .references
-        .iter()
-        .map(|id| semantic.reference(*id))
-        .filter(|reference| with.range().contains_range(reference.range()))
-        .collect();
-
-    // And even with all these restrictions, if the file handle gets used not exactly once,
-    // it doesn't fit the bill.
-    let [reference] = references.as_slice() else {
-        return None;
-    };
-
-    Some(FileOpen {
+    resolve_file_open(
         item,
-        filename,
+        with,
+        semantic,
+        read_mode,
         mode,
         keywords,
-        reference,
-    })
+        OpenArgument::Builtin { filename },
+    )
+}
+
+fn find_path_open<'a>(
+    item: &'a ast::WithItem,
+    with: &'a ast::StmtWith,
+    semantic: &'a SemanticModel<'a>,
+    read_mode: bool,
+    python_version: PythonVersion,
+) -> Option<FileOpen<'a>> {
+    let ast::ExprCall {
+        func,
+        arguments: ast::Arguments { args, keywords, .. },
+        ..
+    } = item.context_expr.as_call_expr()?;
+    if args.iter().any(Expr::is_starred_expr)
+        || keywords.iter().any(|keyword| keyword.arg.is_none())
+    {
+        return None;
+    }
+    if !is_open_call_from_pathlib(func, semantic) {
+        return None;
+    }
+    let attr = func.as_attribute_expr()?;
+    let mode = if args.is_empty() {
+        OpenMode::ReadText
+    } else {
+        match_open_mode(args.first()?)?
+    };
+
+    let (keywords, kw_mode) = match_open_keywords(keywords, read_mode, python_version)?;
+    let mode = kw_mode.unwrap_or(mode);
+    resolve_file_open(
+        item,
+        with,
+        semantic,
+        read_mode,
+        mode,
+        keywords,
+        OpenArgument::Pathlib {
+            path: attr.value.as_ref(),
+        },
+    )
 }
 
 /// Match positional arguments. Return expression for the file name and open mode.

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

@@ -15,7 +15,8 @@ mod tests {
     use crate::test::test_path;
     use crate::{assert_diagnostics, settings};
 
-    #[test_case(Rule::ReadWholeFile, Path::new("FURB101.py"))]
+    #[test_case(Rule::ReadWholeFile, Path::new("FURB101_0.py"))]
+    #[test_case(Rule::ReadWholeFile, Path::new("FURB101_1.py"))]
     #[test_case(Rule::RepeatedAppend, Path::new("FURB113.py"))]
     #[test_case(Rule::IfExpInsteadOfOrOperator, Path::new("FURB110.py"))]
     #[test_case(Rule::ReimplementedOperator, Path::new("FURB118.py"))]
@@ -46,7 +47,8 @@ mod tests {
     #[test_case(Rule::MetaClassABCMeta, Path::new("FURB180.py"))]
     #[test_case(Rule::HashlibDigestHex, Path::new("FURB181.py"))]
     #[test_case(Rule::ListReverseCopy, Path::new("FURB187.py"))]
-    #[test_case(Rule::WriteWholeFile, Path::new("FURB103.py"))]
+    #[test_case(Rule::WriteWholeFile, Path::new("FURB103_0.py"))]
+    #[test_case(Rule::WriteWholeFile, Path::new("FURB103_1.py"))]
     #[test_case(Rule::FStringNumberFormat, Path::new("FURB116.py"))]
     #[test_case(Rule::SortedMinMax, Path::new("FURB192.py"))]
     #[test_case(Rule::SliceToRemovePrefixOrSuffix, Path::new("FURB188.py"))]
@@ -65,7 +67,7 @@ mod tests {
     #[test]
     fn write_whole_file_python_39() -> Result<()> {
         let diagnostics = test_path(
-            Path::new("refurb/FURB103.py"),
+            Path::new("refurb/FURB103_0.py"),
             &settings::LinterSettings::for_rule(Rule::WriteWholeFile)
                 .with_target_version(PythonVersion::PY39),
         )?;

crates/ruff_linter/src/rules/refurb/rules/read_whole_file.rs

@@ -10,7 +10,7 @@ use ruff_text_size::{Ranged, TextRange};
 use crate::checkers::ast::Checker;
 use crate::fix::snippet::SourceCodeSnippet;
 use crate::importer::ImportRequest;
-use crate::rules::refurb::helpers::{FileOpen, find_file_opens};
+use crate::rules::refurb::helpers::{FileOpen, OpenArgument, find_file_opens};
 use crate::{FixAvailability, Violation};
 
 /// ## What it does
@@ -42,27 +42,41 @@ use crate::{FixAvailability, Violation};
 /// - [Python documentation: `Path.read_text`](https://docs.python.org/3/library/pathlib.html#pathlib.Path.read_text)
 #[derive(ViolationMetadata)]
 #[violation_metadata(preview_since = "v0.1.2")]
-pub(crate) struct ReadWholeFile {
+pub(crate) struct ReadWholeFile<'a> {
     filename: SourceCodeSnippet,
     suggestion: SourceCodeSnippet,
+    argument: OpenArgument<'a>,
 }
 
-impl Violation for ReadWholeFile {
+impl Violation for ReadWholeFile<'_> {
     const FIX_AVAILABILITY: FixAvailability = FixAvailability::Sometimes;
 
     #[derive_message_formats]
     fn message(&self) -> String {
         let filename = self.filename.truncated_display();
         let suggestion = self.suggestion.truncated_display();
-        format!("`open` and `read` should be replaced by `Path({filename}).{suggestion}`")
+        match self.argument {
+            OpenArgument::Pathlib { .. } => {
+                format!(
+                    "`Path.open()` followed by `read()` can be replaced by `{filename}.{suggestion}`"
+                )
+            }
+            OpenArgument::Builtin { .. } => {
+                format!("`open` and `read` should be replaced by `Path({filename}).{suggestion}`")
+            }
+        }
     }
 
     fn fix_title(&self) -> Option<String> {
-        Some(format!(
-            "Replace with `Path({}).{}`",
-            self.filename.truncated_display(),
-            self.suggestion.truncated_display(),
-        ))
+        let filename = self.filename.truncated_display();
+        let suggestion = self.suggestion.truncated_display();
+
+        match self.argument {
+            OpenArgument::Pathlib { .. } => Some(format!("Replace with `{filename}.{suggestion}`")),
+            OpenArgument::Builtin { .. } => {
+                Some(format!("Replace with `Path({filename}).{suggestion}`"))
+            }
+        }
     }
 }
 
@@ -114,13 +128,13 @@ impl<'a> Visitor<'a> for ReadMatcher<'a, '_> {
                 .position(|open| open.is_ref(read_from))
             {
                 let open = self.candidates.remove(open);
+                let filename_display = open.argument.display(self.checker.source());
                 let suggestion = make_suggestion(&open, self.checker.generator());
                 let mut diagnostic = self.checker.report_diagnostic(
                     ReadWholeFile {
-                        filename: SourceCodeSnippet::from_str(
-                            &self.checker.generator().expr(open.filename),
-                        ),
+                        filename: SourceCodeSnippet::from_str(filename_display),
                         suggestion: SourceCodeSnippet::from_str(&suggestion),
+                        argument: open.argument,
                     },
                     open.item.range(),
                 );
@@ -188,8 +202,6 @@ fn generate_fix(
 
     let locator = checker.locator();
 
-    let filename_code = locator.slice(open.filename.range());
-
     let (import_edit, binding) = checker
         .importer()
         .get_or_import_symbol(
@@ -206,10 +218,15 @@ fn generate_fix(
         [Stmt::Assign(ast::StmtAssign { targets, value, .. })] if value.range() == expr.range() => {
             match targets.as_slice() {
                 [Expr::Name(name)] => {
-                    format!(
-                        "{name} = {binding}({filename_code}).{suggestion}",
-                        name = name.id
-                    )
+                    let target = match open.argument {
+                        OpenArgument::Builtin { filename } => {
+                            let filename_code = locator.slice(filename.range());
+                            format!("{binding}({filename_code})")
+                        }
+                        OpenArgument::Pathlib { path } => locator.slice(path.range()).to_string(),
+                    };
+
+                    format!("{name} = {target}.{suggestion}", name = name.id)
                 }
                 _ => return None,
             }
@@ -223,8 +240,16 @@ fn generate_fix(
             }),
         ] if value.range() == expr.range() => match target.as_ref() {
             Expr::Name(name) => {
+                let target = match open.argument {
+                    OpenArgument::Builtin { filename } => {
+                        let filename_code = locator.slice(filename.range());
+                        format!("{binding}({filename_code})")
+                    }
+                    OpenArgument::Pathlib { path } => locator.slice(path.range()).to_string(),
+                };
+
                 format!(
-                    "{var}: {ann} = {binding}({filename_code}).{suggestion}",
+                    "{var}: {ann} = {target}.{suggestion}",
                     var = name.id,
                     ann = locator.slice(annotation.range())
                 )

crates/ruff_linter/src/rules/refurb/rules/repeated_append.rs

@@ -176,7 +176,7 @@ fn match_consecutive_appends<'a>(
     let suite = if semantic.at_top_level() {
         // If the statement is at the top level, we should go to the parent module.
         // Module is available in the definitions list.
-        EnclosingSuite::new(semantic.definitions.python_ast()?, stmt)?
+        EnclosingSuite::new(semantic.definitions.python_ast()?, stmt.into())?
     } else {
         // Otherwise, go to the parent, and take its body as a sequence of siblings.
         semantic

crates/ruff_linter/src/rules/refurb/rules/write_whole_file.rs

@@ -9,7 +9,7 @@ use ruff_text_size::Ranged;
 use crate::checkers::ast::Checker;
 use crate::fix::snippet::SourceCodeSnippet;
 use crate::importer::ImportRequest;
-use crate::rules::refurb::helpers::{FileOpen, find_file_opens};
+use crate::rules::refurb::helpers::{FileOpen, OpenArgument, find_file_opens};
 use crate::{FixAvailability, Locator, Violation};
 
 /// ## What it does
@@ -42,26 +42,40 @@ use crate::{FixAvailability, Locator, Violation};
 /// - [Python documentation: `Path.write_text`](https://docs.python.org/3/library/pathlib.html#pathlib.Path.write_text)
 #[derive(ViolationMetadata)]
 #[violation_metadata(preview_since = "v0.3.6")]
-pub(crate) struct WriteWholeFile {
+pub(crate) struct WriteWholeFile<'a> {
     filename: SourceCodeSnippet,
     suggestion: SourceCodeSnippet,
+    argument: OpenArgument<'a>,
 }
 
-impl Violation for WriteWholeFile {
+impl Violation for WriteWholeFile<'_> {
     const FIX_AVAILABILITY: FixAvailability = FixAvailability::Sometimes;
 
     #[derive_message_formats]
     fn message(&self) -> String {
         let filename = self.filename.truncated_display();
         let suggestion = self.suggestion.truncated_display();
-        format!("`open` and `write` should be replaced by `Path({filename}).{suggestion}`")
+        match self.argument {
+            OpenArgument::Pathlib { .. } => {
+                format!(
+                    "`Path.open()` followed by `write()` can be replaced by `{filename}.{suggestion}`"
+                )
+            }
+            OpenArgument::Builtin { .. } => {
+                format!("`open` and `write` should be replaced by `Path({filename}).{suggestion}`")
+            }
+        }
     }
     fn fix_title(&self) -> Option<String> {
-        Some(format!(
-            "Replace with `Path({}).{}`",
-            self.filename.truncated_display(),
-            self.suggestion.truncated_display(),
-        ))
+        let filename = self.filename.truncated_display();
+        let suggestion = self.suggestion.truncated_display();
+
+        match self.argument {
+            OpenArgument::Pathlib { .. } => Some(format!("Replace with `{filename}.{suggestion}`")),
+            OpenArgument::Builtin { .. } => {
+                Some(format!("Replace with `Path({filename}).{suggestion}`"))
+            }
+        }
     }
 }
 
@@ -125,16 +139,15 @@ impl<'a> Visitor<'a> for WriteMatcher<'a, '_> {
                 .position(|open| open.is_ref(write_to))
             {
                 let open = self.candidates.remove(open);
-
                 if self.loop_counter == 0 {
+                    let filename_display = open.argument.display(self.checker.source());
                     let suggestion = make_suggestion(&open, content, self.checker.locator());
 
                     let mut diagnostic = self.checker.report_diagnostic(
                         WriteWholeFile {
-                            filename: SourceCodeSnippet::from_str(
-                                &self.checker.generator().expr(open.filename),
-                            ),
+                            filename: SourceCodeSnippet::from_str(filename_display),
                             suggestion: SourceCodeSnippet::from_str(&suggestion),
+                            argument: open.argument,
                         },
                         open.item.range(),
                     );
@@ -198,7 +211,6 @@ fn generate_fix(
     }
 
     let locator = checker.locator();
-    let filename_code = locator.slice(open.filename.range());
 
     let (import_edit, binding) = checker
         .importer()
@@ -209,7 +221,15 @@ fn generate_fix(
         )
         .ok()?;
 
-    let replacement = format!("{binding}({filename_code}).{suggestion}");
+    let target = match open.argument {
+        OpenArgument::Builtin { filename } => {
+            let filename_code = locator.slice(filename.range());
+            format!("{binding}({filename_code})")
+        }
+        OpenArgument::Pathlib { path } => locator.slice(path.range()).to_string(),
+    };
+
+    let replacement = format!("{target}.{suggestion}");
 
     let applicability = if checker.comment_ranges().intersects(with_stmt.range()) {
         Applicability::Unsafe

crates/ruff_linter/src/rules/refurb/snapshots/ruff_linter__rules__refurb__tests__FURB101_FURB101_0.py.snap

@@ -2,7 +2,7 @@
 source: crates/ruff_linter/src/rules/refurb/mod.rs
 ---
 FURB101 [*] `open` and `read` should be replaced by `Path("file.txt").read_text()`
-  --> FURB101.py:12:6
+  --> FURB101_0.py:12:6
    |
 11 | # FURB101
 12 | with open("file.txt") as f:
@@ -26,7 +26,7 @@ help: Replace with `Path("file.txt").read_text()`
 16 | with open("file.txt", "rb") as f:
 
 FURB101 [*] `open` and `read` should be replaced by `Path("file.txt").read_bytes()`
-  --> FURB101.py:16:6
+  --> FURB101_0.py:16:6
    |
 15 | # FURB101
 16 | with open("file.txt", "rb") as f:
@@ -50,7 +50,7 @@ help: Replace with `Path("file.txt").read_bytes()`
 20 | with open("file.txt", mode="rb") as f:
 
 FURB101 [*] `open` and `read` should be replaced by `Path("file.txt").read_bytes()`
-  --> FURB101.py:20:6
+  --> FURB101_0.py:20:6
    |
 19 | # FURB101
 20 | with open("file.txt", mode="rb") as f:
@@ -74,7 +74,7 @@ help: Replace with `Path("file.txt").read_bytes()`
 24 | with open("file.txt", encoding="utf8") as f:
 
 FURB101 [*] `open` and `read` should be replaced by `Path("file.txt").read_text(encoding="utf8")`
-  --> FURB101.py:24:6
+  --> FURB101_0.py:24:6
    |
 23 | # FURB101
 24 | with open("file.txt", encoding="utf8") as f:
@@ -98,7 +98,7 @@ help: Replace with `Path("file.txt").read_text(encoding="utf8")`
 28 | with open("file.txt", errors="ignore") as f:
 
 FURB101 [*] `open` and `read` should be replaced by `Path("file.txt").read_text(errors="ignore")`
-  --> FURB101.py:28:6
+  --> FURB101_0.py:28:6
    |
 27 | # FURB101
 28 | with open("file.txt", errors="ignore") as f:
@@ -122,7 +122,7 @@ help: Replace with `Path("file.txt").read_text(errors="ignore")`
 32 | with open("file.txt", mode="r") as f:  # noqa: FURB120
 
 FURB101 [*] `open` and `read` should be replaced by `Path("file.txt").read_text()`
-  --> FURB101.py:32:6
+  --> FURB101_0.py:32:6
    |
 31 | # FURB101
 32 | with open("file.txt", mode="r") as f:  # noqa: FURB120
@@ -147,7 +147,7 @@ help: Replace with `Path("file.txt").read_text()`
 note: This is an unsafe fix and may change runtime behavior
 
 FURB101 `open` and `read` should be replaced by `Path(foo()).read_bytes()`
-  --> FURB101.py:36:6
+  --> FURB101_0.py:36:6
    |
 35 | # FURB101
 36 | with open(foo(), "rb") as f:
@@ -158,7 +158,7 @@ FURB101 `open` and `read` should be replaced by `Path(foo()).read_bytes()`
 help: Replace with `Path(foo()).read_bytes()`
 
 FURB101 `open` and `read` should be replaced by `Path("a.txt").read_text()`
-  --> FURB101.py:44:6
+  --> FURB101_0.py:44:6
    |
 43 | # FURB101
 44 | with open("a.txt") as a, open("b.txt", "rb") as b:
@@ -169,7 +169,7 @@ FURB101 `open` and `read` should be replaced by `Path("a.txt").read_text()`
 help: Replace with `Path("a.txt").read_text()`
 
 FURB101 `open` and `read` should be replaced by `Path("b.txt").read_bytes()`
-  --> FURB101.py:44:26
+  --> FURB101_0.py:44:26
    |
 43 | # FURB101
 44 | with open("a.txt") as a, open("b.txt", "rb") as b:
@@ -180,7 +180,7 @@ FURB101 `open` and `read` should be replaced by `Path("b.txt").read_bytes()`
 help: Replace with `Path("b.txt").read_bytes()`
 
 FURB101 `open` and `read` should be replaced by `Path("file.txt").read_text()`
-  --> FURB101.py:49:18
+  --> FURB101_0.py:49:18
    |
 48 | # FURB101
 49 | with foo() as a, open("file.txt") as b, foo() as c:
@@ -191,7 +191,7 @@ FURB101 `open` and `read` should be replaced by `Path("file.txt").read_text()`
 help: Replace with `Path("file.txt").read_text()`
 
 FURB101 [*] `open` and `read` should be replaced by `Path("file.txt").read_text(encoding="utf-8")`
-   --> FURB101.py:130:6
+   --> FURB101_0.py:130:6
     |
 129 | # FURB101
 130 | with open("file.txt", encoding="utf-8") as f:
@@ -215,7 +215,7 @@ help: Replace with `Path("file.txt").read_text(encoding="utf-8")`
 134 | with open("file.txt", encoding="utf-8") as f:
 
 FURB101 `open` and `read` should be replaced by `Path("file.txt").read_text(encoding="utf-8")`
-   --> FURB101.py:134:6
+   --> FURB101_0.py:134:6
     |
 133 | # FURB101 but no fix because it would remove the assignment to `x`
 134 | with open("file.txt", encoding="utf-8") as f:
@@ -225,7 +225,7 @@ FURB101 `open` and `read` should be replaced by `Path("file.txt").read_text(enco
 help: Replace with `Path("file.txt").read_text(encoding="utf-8")`
 
 FURB101 `open` and `read` should be replaced by `Path("file.txt").read_text(encoding="utf-8")`
-   --> FURB101.py:138:6
+   --> FURB101_0.py:138:6
     |
 137 | # FURB101 but no fix because it would remove the `process_contents` call
 138 | with open("file.txt", encoding="utf-8") as f:
@@ -234,13 +234,13 @@ FURB101 `open` and `read` should be replaced by `Path("file.txt").read_text(enco
     |
 help: Replace with `Path("file.txt").read_text(encoding="utf-8")`
 
-FURB101 `open` and `read` should be replaced by `Path("file.txt").read_text(encoding="utf-8")`
-   --> FURB101.py:141:6
+FURB101 `open` and `read` should be replaced by `Path("file1.txt").read_text(encoding="utf-8")`
+   --> FURB101_0.py:141:6
     |
 139 |     contents = process_contents(f.read())
 140 |
-141 | with open("file.txt", encoding="utf-8") as f:
-    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+141 | with open("file1.txt", encoding="utf-8") as f:
+    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 142 |     contents: str = process_contents(f.read())
     |
-help: Replace with `Path("file.txt").read_text(encoding="utf-8")`
+help: Replace with `Path("file1.txt").read_text(encoding="utf-8")`

crates/ruff_linter/src/rules/refurb/snapshots/ruff_linter__rules__refurb__tests__FURB101_FURB101_1.py.snap

@@ -0,0 +1,39 @@
+---
+source: crates/ruff_linter/src/rules/refurb/mod.rs
+---
+FURB101 [*] `Path.open()` followed by `read()` can be replaced by `Path("file.txt").read_text()`
+ --> FURB101_1.py:4:6
+  |
+2 | from pathlib import Path
+3 |
+4 | with Path("file.txt").open() as f:
+  |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+5 |     contents = f.read()
+  |
+help: Replace with `Path("file.txt").read_text()`
+1 | 
+2 | from pathlib import Path
+3 | 
+  - with Path("file.txt").open() as f:
+  -     contents = f.read()
+4 + contents = Path("file.txt").read_text()
+5 | 
+6 | with Path("file.txt").open("r") as f:
+7 |     contents = f.read()
+
+FURB101 [*] `Path.open()` followed by `read()` can be replaced by `Path("file.txt").read_text()`
+ --> FURB101_1.py:7:6
+  |
+5 |     contents = f.read()
+6 |
+7 | with Path("file.txt").open("r") as f:
+  |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+8 |     contents = f.read()
+  |
+help: Replace with `Path("file.txt").read_text()`
+4 | with Path("file.txt").open() as f:
+5 |     contents = f.read()
+6 | 
+  - with Path("file.txt").open("r") as f:
+  -     contents = f.read()
+7 + contents = Path("file.txt").read_text()

crates/ruff_linter/src/rules/refurb/snapshots/ruff_linter__rules__refurb__tests__FURB103_FURB103_0.py.snap

@@ -2,7 +2,7 @@
 source: crates/ruff_linter/src/rules/refurb/mod.rs
 ---
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text("test")`
-  --> FURB103.py:12:6
+  --> FURB103_0.py:12:6
    |
 11 | # FURB103
 12 | with open("file.txt", "w") as f:
@@ -26,7 +26,7 @@ help: Replace with `Path("file.txt").write_text("test")`
 16 | with open("file.txt", "wb") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_bytes(foobar)`
-  --> FURB103.py:16:6
+  --> FURB103_0.py:16:6
    |
 15 | # FURB103
 16 | with open("file.txt", "wb") as f:
@@ -50,7 +50,7 @@ help: Replace with `Path("file.txt").write_bytes(foobar)`
 20 | with open("file.txt", mode="wb") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_bytes(b"abc")`
-  --> FURB103.py:20:6
+  --> FURB103_0.py:20:6
    |
 19 | # FURB103
 20 | with open("file.txt", mode="wb") as f:
@@ -74,7 +74,7 @@ help: Replace with `Path("file.txt").write_bytes(b"abc")`
 24 | with open("file.txt", "w", encoding="utf8") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar, encoding="utf8")`
-  --> FURB103.py:24:6
+  --> FURB103_0.py:24:6
    |
 23 | # FURB103
 24 | with open("file.txt", "w", encoding="utf8") as f:
@@ -98,7 +98,7 @@ help: Replace with `Path("file.txt").write_text(foobar, encoding="utf8")`
 28 | with open("file.txt", "w", errors="ignore") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar, errors="ignore")`
-  --> FURB103.py:28:6
+  --> FURB103_0.py:28:6
    |
 27 | # FURB103
 28 | with open("file.txt", "w", errors="ignore") as f:
@@ -122,7 +122,7 @@ help: Replace with `Path("file.txt").write_text(foobar, errors="ignore")`
 32 | with open("file.txt", mode="w") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar)`
-  --> FURB103.py:32:6
+  --> FURB103_0.py:32:6
    |
 31 | # FURB103
 32 | with open("file.txt", mode="w") as f:
@@ -146,7 +146,7 @@ help: Replace with `Path("file.txt").write_text(foobar)`
 36 | with open(foo(), "wb") as f:
 
 FURB103 `open` and `write` should be replaced by `Path(foo()).write_bytes(bar())`
-  --> FURB103.py:36:6
+  --> FURB103_0.py:36:6
    |
 35 | # FURB103
 36 | with open(foo(), "wb") as f:
@@ -157,7 +157,7 @@ FURB103 `open` and `write` should be replaced by `Path(foo()).write_bytes(bar())
 help: Replace with `Path(foo()).write_bytes(bar())`
 
 FURB103 `open` and `write` should be replaced by `Path("a.txt").write_text(x)`
-  --> FURB103.py:44:6
+  --> FURB103_0.py:44:6
    |
 43 | # FURB103
 44 | with open("a.txt", "w") as a, open("b.txt", "wb") as b:
@@ -168,7 +168,7 @@ FURB103 `open` and `write` should be replaced by `Path("a.txt").write_text(x)`
 help: Replace with `Path("a.txt").write_text(x)`
 
 FURB103 `open` and `write` should be replaced by `Path("b.txt").write_bytes(y)`
-  --> FURB103.py:44:31
+  --> FURB103_0.py:44:31
    |
 43 | # FURB103
 44 | with open("a.txt", "w") as a, open("b.txt", "wb") as b:
@@ -179,7 +179,7 @@ FURB103 `open` and `write` should be replaced by `Path("b.txt").write_bytes(y)`
 help: Replace with `Path("b.txt").write_bytes(y)`
 
 FURB103 `open` and `write` should be replaced by `Path("file.txt").write_text(bar(bar(a + x)))`
-  --> FURB103.py:49:18
+  --> FURB103_0.py:49:18
    |
 48 | # FURB103
 49 | with foo() as a, open("file.txt", "w") as b, foo() as c:
@@ -190,7 +190,7 @@ FURB103 `open` and `write` should be replaced by `Path("file.txt").write_text(ba
 help: Replace with `Path("file.txt").write_text(bar(bar(a + x)))`
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar, newline="\r\n")`
-  --> FURB103.py:58:6
+  --> FURB103_0.py:58:6
    |
 57 | # FURB103
 58 | with open("file.txt", "w", newline="\r\n") as f:
@@ -214,7 +214,7 @@ help: Replace with `Path("file.txt").write_text(foobar, newline="\r\n")`
 62 | import builtins
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar, newline="\r\n")`
-  --> FURB103.py:66:6
+  --> FURB103_0.py:66:6
    |
 65 | # FURB103
 66 | with builtins.open("file.txt", "w", newline="\r\n") as f:
@@ -237,7 +237,7 @@ help: Replace with `Path("file.txt").write_text(foobar, newline="\r\n")`
 70 | from builtins import open as o
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar, newline="\r\n")`
-  --> FURB103.py:74:6
+  --> FURB103_0.py:74:6
    |
 73 | # FURB103
 74 | with o("file.txt", "w", newline="\r\n") as f:
@@ -260,7 +260,7 @@ help: Replace with `Path("file.txt").write_text(foobar, newline="\r\n")`
 78 | 
 
 FURB103 [*] `open` and `write` should be replaced by `Path("test.json")....`
-   --> FURB103.py:154:6
+   --> FURB103_0.py:154:6
     |
 152 | data = {"price": 100}
 153 |
@@ -284,7 +284,7 @@ help: Replace with `Path("test.json")....`
 158 | with open("tmp_path/pyproject.toml", "w") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("tmp_path/pyproject.toml")....`
-   --> FURB103.py:158:6
+   --> FURB103_0.py:158:6
     |
 157 | # See: https://github.com/astral-sh/ruff/issues/21381
 158 | with open("tmp_path/pyproject.toml", "w") as f:

crates/ruff_linter/src/rules/refurb/snapshots/ruff_linter__rules__refurb__tests__FURB103_FURB103_1.py.snap

@@ -0,0 +1,157 @@
+---
+source: crates/ruff_linter/src/rules/refurb/mod.rs
+---
+FURB103 [*] `Path.open()` followed by `write()` can be replaced by `Path("file.txt").write_text("test")`
+ --> FURB103_1.py:3:6
+  |
+1 | from pathlib import Path
+2 |
+3 | with Path("file.txt").open("w") as f:
+  |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+4 |     f.write("test")
+  |
+help: Replace with `Path("file.txt").write_text("test")`
+1 | from pathlib import Path
+2 | 
+  - with Path("file.txt").open("w") as f:
+  -     f.write("test")
+3 + Path("file.txt").write_text("test")
+4 | 
+5 | with Path("file.txt").open("wb") as f:
+6 |     f.write(b"test")
+
+FURB103 [*] `Path.open()` followed by `write()` can be replaced by `Path("file.txt").write_bytes(b"test")`
+ --> FURB103_1.py:6:6
+  |
+4 |     f.write("test")
+5 |
+6 | with Path("file.txt").open("wb") as f:
+  |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+7 |     f.write(b"test")
+  |
+help: Replace with `Path("file.txt").write_bytes(b"test")`
+3 | with Path("file.txt").open("w") as f:
+4 |     f.write("test")
+5 | 
+  - with Path("file.txt").open("wb") as f:
+  -     f.write(b"test")
+6 + Path("file.txt").write_bytes(b"test")
+7 | 
+8 | with Path("file.txt").open(mode="w") as f:
+9 |     f.write("test")
+
+FURB103 [*] `Path.open()` followed by `write()` can be replaced by `Path("file.txt").write_text("test")`
+  --> FURB103_1.py:9:6
+   |
+ 7 |     f.write(b"test")
+ 8 |
+ 9 | with Path("file.txt").open(mode="w") as f:
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+10 |     f.write("test")
+   |
+help: Replace with `Path("file.txt").write_text("test")`
+6  | with Path("file.txt").open("wb") as f:
+7  |     f.write(b"test")
+8  | 
+   - with Path("file.txt").open(mode="w") as f:
+   -     f.write("test")
+9  + Path("file.txt").write_text("test")
+10 | 
+11 | with Path("file.txt").open("w", encoding="utf8") as f:
+12 |     f.write("test")
+
+FURB103 [*] `Path.open()` followed by `write()` can be replaced by `Path("file.txt").write_text("test", encoding="utf8")`
+  --> FURB103_1.py:12:6
+   |
+10 |     f.write("test")
+11 |
+12 | with Path("file.txt").open("w", encoding="utf8") as f:
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+13 |     f.write("test")
+   |
+help: Replace with `Path("file.txt").write_text("test", encoding="utf8")`
+9  | with Path("file.txt").open(mode="w") as f:
+10 |     f.write("test")
+11 | 
+   - with Path("file.txt").open("w", encoding="utf8") as f:
+   -     f.write("test")
+12 + Path("file.txt").write_text("test", encoding="utf8")
+13 | 
+14 | with Path("file.txt").open("w", errors="ignore") as f:
+15 |     f.write("test")
+
+FURB103 [*] `Path.open()` followed by `write()` can be replaced by `Path("file.txt").write_text("test", errors="ignore")`
+  --> FURB103_1.py:15:6
+   |
+13 |     f.write("test")
+14 |
+15 | with Path("file.txt").open("w", errors="ignore") as f:
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+16 |     f.write("test")
+   |
+help: Replace with `Path("file.txt").write_text("test", errors="ignore")`
+12 | with Path("file.txt").open("w", encoding="utf8") as f:
+13 |     f.write("test")
+14 | 
+   - with Path("file.txt").open("w", errors="ignore") as f:
+   -     f.write("test")
+15 + Path("file.txt").write_text("test", errors="ignore")
+16 | 
+17 | with Path(foo()).open("w") as f:
+18 |     f.write("test")
+
+FURB103 [*] `Path.open()` followed by `write()` can be replaced by `Path(foo()).write_text("test")`
+  --> FURB103_1.py:18:6
+   |
+16 |     f.write("test")
+17 |
+18 | with Path(foo()).open("w") as f:
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^
+19 |     f.write("test")
+   |
+help: Replace with `Path(foo()).write_text("test")`
+15 | with Path("file.txt").open("w", errors="ignore") as f:
+16 |     f.write("test")
+17 | 
+   - with Path(foo()).open("w") as f:
+   -     f.write("test")
+18 + Path(foo()).write_text("test")
+19 | 
+20 | p = Path("file.txt")
+21 | with p.open("w") as f:
+
+FURB103 [*] `Path.open()` followed by `write()` can be replaced by `p.write_text("test")`
+  --> FURB103_1.py:22:6
+   |
+21 | p = Path("file.txt")
+22 | with p.open("w") as f:
+   |      ^^^^^^^^^^^^^^^^
+23 |     f.write("test")
+   |
+help: Replace with `p.write_text("test")`
+19 |     f.write("test")
+20 | 
+21 | p = Path("file.txt")
+   - with p.open("w") as f:
+   -     f.write("test")
+22 + p.write_text("test")
+23 | 
+24 | with Path("foo", "bar", "baz").open("w") as f:
+25 |     f.write("test")
+
+FURB103 [*] `Path.open()` followed by `write()` can be replaced by `Path("foo", "bar", "baz").write_text("test")`
+  --> FURB103_1.py:25:6
+   |
+23 |     f.write("test")
+24 |
+25 | with Path("foo", "bar", "baz").open("w") as f:
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+26 |     f.write("test")
+   |
+help: Replace with `Path("foo", "bar", "baz").write_text("test")`
+22 | with p.open("w") as f:
+23 |     f.write("test")
+24 | 
+   - with Path("foo", "bar", "baz").open("w") as f:
+   -     f.write("test")
+25 + Path("foo", "bar", "baz").write_text("test")

crates/ruff_linter/src/rules/refurb/snapshots/ruff_linter__rules__refurb__tests__write_whole_file_python_39.snap

@@ -2,7 +2,7 @@
 source: crates/ruff_linter/src/rules/refurb/mod.rs
 ---
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text("test")`
-  --> FURB103.py:12:6
+  --> FURB103_0.py:12:6
    |
 11 | # FURB103
 12 | with open("file.txt", "w") as f:
@@ -26,7 +26,7 @@ help: Replace with `Path("file.txt").write_text("test")`
 16 | with open("file.txt", "wb") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_bytes(foobar)`
-  --> FURB103.py:16:6
+  --> FURB103_0.py:16:6
    |
 15 | # FURB103
 16 | with open("file.txt", "wb") as f:
@@ -50,7 +50,7 @@ help: Replace with `Path("file.txt").write_bytes(foobar)`
 20 | with open("file.txt", mode="wb") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_bytes(b"abc")`
-  --> FURB103.py:20:6
+  --> FURB103_0.py:20:6
    |
 19 | # FURB103
 20 | with open("file.txt", mode="wb") as f:
@@ -74,7 +74,7 @@ help: Replace with `Path("file.txt").write_bytes(b"abc")`
 24 | with open("file.txt", "w", encoding="utf8") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar, encoding="utf8")`
-  --> FURB103.py:24:6
+  --> FURB103_0.py:24:6
    |
 23 | # FURB103
 24 | with open("file.txt", "w", encoding="utf8") as f:
@@ -98,7 +98,7 @@ help: Replace with `Path("file.txt").write_text(foobar, encoding="utf8")`
 28 | with open("file.txt", "w", errors="ignore") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar, errors="ignore")`
-  --> FURB103.py:28:6
+  --> FURB103_0.py:28:6
    |
 27 | # FURB103
 28 | with open("file.txt", "w", errors="ignore") as f:
@@ -122,7 +122,7 @@ help: Replace with `Path("file.txt").write_text(foobar, errors="ignore")`
 32 | with open("file.txt", mode="w") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("file.txt").write_text(foobar)`
-  --> FURB103.py:32:6
+  --> FURB103_0.py:32:6
    |
 31 | # FURB103
 32 | with open("file.txt", mode="w") as f:
@@ -146,7 +146,7 @@ help: Replace with `Path("file.txt").write_text(foobar)`
 36 | with open(foo(), "wb") as f:
 
 FURB103 `open` and `write` should be replaced by `Path(foo()).write_bytes(bar())`
-  --> FURB103.py:36:6
+  --> FURB103_0.py:36:6
    |
 35 | # FURB103
 36 | with open(foo(), "wb") as f:
@@ -157,7 +157,7 @@ FURB103 `open` and `write` should be replaced by `Path(foo()).write_bytes(bar())
 help: Replace with `Path(foo()).write_bytes(bar())`
 
 FURB103 `open` and `write` should be replaced by `Path("a.txt").write_text(x)`
-  --> FURB103.py:44:6
+  --> FURB103_0.py:44:6
    |
 43 | # FURB103
 44 | with open("a.txt", "w") as a, open("b.txt", "wb") as b:
@@ -168,7 +168,7 @@ FURB103 `open` and `write` should be replaced by `Path("a.txt").write_text(x)`
 help: Replace with `Path("a.txt").write_text(x)`
 
 FURB103 `open` and `write` should be replaced by `Path("b.txt").write_bytes(y)`
-  --> FURB103.py:44:31
+  --> FURB103_0.py:44:31
    |
 43 | # FURB103
 44 | with open("a.txt", "w") as a, open("b.txt", "wb") as b:
@@ -179,7 +179,7 @@ FURB103 `open` and `write` should be replaced by `Path("b.txt").write_bytes(y)`
 help: Replace with `Path("b.txt").write_bytes(y)`
 
 FURB103 `open` and `write` should be replaced by `Path("file.txt").write_text(bar(bar(a + x)))`
-  --> FURB103.py:49:18
+  --> FURB103_0.py:49:18
    |
 48 | # FURB103
 49 | with foo() as a, open("file.txt", "w") as b, foo() as c:
@@ -190,7 +190,7 @@ FURB103 `open` and `write` should be replaced by `Path("file.txt").write_text(ba
 help: Replace with `Path("file.txt").write_text(bar(bar(a + x)))`
 
 FURB103 [*] `open` and `write` should be replaced by `Path("test.json")....`
-   --> FURB103.py:154:6
+   --> FURB103_0.py:154:6
     |
 152 | data = {"price": 100}
 153 |
@@ -214,7 +214,7 @@ help: Replace with `Path("test.json")....`
 158 | with open("tmp_path/pyproject.toml", "w") as f:
 
 FURB103 [*] `open` and `write` should be replaced by `Path("tmp_path/pyproject.toml")....`
-   --> FURB103.py:158:6
+   --> FURB103_0.py:158:6
     |
 157 | # See: https://github.com/astral-sh/ruff/issues/21381
 158 | with open("tmp_path/pyproject.toml", "w") as f:

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

@@ -313,12 +313,20 @@ mod tests {
                 Rule::UnusedVariable,
                 Rule::AmbiguousVariableName,
                 Rule::UnusedNOQA,
-            ]),
+                Rule::InvalidRuleCode,
+                Rule::InvalidSuppressionComment,
+                Rule::UnmatchedSuppressionComment,
+            ])
+            .with_external_rules(&["TK421"]),
             &settings::LinterSettings::for_rules(vec![
                 Rule::UnusedVariable,
                 Rule::AmbiguousVariableName,
                 Rule::UnusedNOQA,
+                Rule::InvalidRuleCode,
+                Rule::InvalidSuppressionComment,
+                Rule::UnmatchedSuppressionComment,
             ])
+            .with_external_rules(&["TK421"])
             .with_preview_mode(),
         );
         Ok(())

crates/ruff_linter/src/rules/ruff/rules/invalid_rule_code.rs

@@ -9,6 +9,21 @@ use crate::registry::Rule;
 use crate::rule_redirects::get_redirect_target;
 use crate::{AlwaysFixableViolation, Edit, Fix};
 
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) enum InvalidRuleCodeKind {
+    Noqa,
+    Suppression,
+}
+
+impl InvalidRuleCodeKind {
+    fn as_str(&self) -> &str {
+        match self {
+            InvalidRuleCodeKind::Noqa => "`# noqa`",
+            InvalidRuleCodeKind::Suppression => "suppression",
+        }
+    }
+}
+
 /// ## What it does
 /// Checks for `noqa` codes that are invalid.
 ///
@@ -36,12 +51,17 @@ use crate::{AlwaysFixableViolation, Edit, Fix};
 #[violation_metadata(preview_since = "0.11.4")]
 pub(crate) struct InvalidRuleCode {
     pub(crate) rule_code: String,
+    pub(crate) kind: InvalidRuleCodeKind,
 }
 
 impl AlwaysFixableViolation for InvalidRuleCode {
     #[derive_message_formats]
     fn message(&self) -> String {
-        format!("Invalid rule code in `# noqa`: {}", self.rule_code)
+        format!(
+            "Invalid rule code in {}: {}",
+            self.kind.as_str(),
+            self.rule_code
+        )
     }
 
     fn fix_title(&self) -> String {
@@ -61,7 +81,9 @@ pub(crate) fn invalid_noqa_code(
             continue;
         };
 
-        let all_valid = directive.iter().all(|code| code_is_valid(code, external));
+        let all_valid = directive
+            .iter()
+            .all(|code| code_is_valid(code.as_str(), external));
 
         if all_valid {
             continue;
@@ -69,7 +91,7 @@ pub(crate) fn invalid_noqa_code(
 
         let (valid_codes, invalid_codes): (Vec<_>, Vec<_>) = directive
             .iter()
-            .partition(|&code| code_is_valid(code, external));
+            .partition(|&code| code_is_valid(code.as_str(), external));
 
         if valid_codes.is_empty() {
             all_codes_invalid_diagnostic(directive, invalid_codes, context);
@@ -81,10 +103,9 @@ pub(crate) fn invalid_noqa_code(
     }
 }
 
-fn code_is_valid(code: &Code, external: &[String]) -> bool {
-    let code_str = code.as_str();
-    Rule::from_code(get_redirect_target(code_str).unwrap_or(code_str)).is_ok()
-        || external.iter().any(|ext| code_str.starts_with(ext))
+pub(crate) fn code_is_valid(code: &str, external: &[String]) -> bool {
+    Rule::from_code(get_redirect_target(code).unwrap_or(code)).is_ok()
+        || external.iter().any(|ext| code.starts_with(ext))
 }
 
 fn all_codes_invalid_diagnostic(
@@ -100,6 +121,7 @@ fn all_codes_invalid_diagnostic(
                     .map(Code::as_str)
                     .collect::<Vec<_>>()
                     .join(", "),
+                kind: InvalidRuleCodeKind::Noqa,
             },
             directive.range(),
         )
@@ -116,6 +138,7 @@ fn some_codes_are_invalid_diagnostic(
         .report_diagnostic(
             InvalidRuleCode {
                 rule_code: invalid_code.to_string(),
+                kind: InvalidRuleCodeKind::Noqa,
             },
             invalid_code.range(),
         )

crates/ruff_linter/src/rules/ruff/rules/invalid_suppression_comment.rs

@@ -0,0 +1,59 @@
+use ruff_macros::{ViolationMetadata, derive_message_formats};
+
+use crate::AlwaysFixableViolation;
+use crate::suppression::{InvalidSuppressionKind, ParseErrorKind};
+
+/// ## What it does
+/// Checks for invalid suppression comments
+///
+/// ## Why is this bad?
+/// Invalid suppression comments are ignored by Ruff, and should either
+/// be fixed or removed to avoid confusion.
+///
+/// ## Example
+/// ```python
+/// ruff: disable  # missing codes
+/// ```
+///
+/// Use instead:
+/// ```python
+/// # ruff: disable[E501]
+/// ```
+///
+/// Or delete the invalid suppression comment.
+///
+/// ## References
+/// - [Ruff error suppression](https://docs.astral.sh/ruff/linter/#error-suppression)
+#[derive(ViolationMetadata)]
+#[violation_metadata(preview_since = "0.14.11")]
+pub(crate) struct InvalidSuppressionComment {
+    pub(crate) kind: InvalidSuppressionCommentKind,
+}
+
+impl AlwaysFixableViolation for InvalidSuppressionComment {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let msg = match self.kind {
+            InvalidSuppressionCommentKind::Invalid(InvalidSuppressionKind::Indentation) => {
+                "unexpected indentation".to_string()
+            }
+            InvalidSuppressionCommentKind::Invalid(InvalidSuppressionKind::Trailing) => {
+                "trailing comments are not supported".to_string()
+            }
+            InvalidSuppressionCommentKind::Invalid(InvalidSuppressionKind::Unmatched) => {
+                "no matching 'disable' comment".to_string()
+            }
+            InvalidSuppressionCommentKind::Error(error) => format!("{error}"),
+        };
+        format!("Invalid suppression comment: {msg}")
+    }
+
+    fn fix_title(&self) -> String {
+        "Remove suppression comment".to_string()
+    }
+}
+
+pub(crate) enum InvalidSuppressionCommentKind {
+    Invalid(InvalidSuppressionKind),
+    Error(ParseErrorKind),
+}

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

@@ -22,6 +22,7 @@ pub(crate) use invalid_formatter_suppression_comment::*;
 pub(crate) use invalid_index_type::*;
 pub(crate) use invalid_pyproject_toml::*;
 pub(crate) use invalid_rule_code::*;
+pub(crate) use invalid_suppression_comment::*;
 pub(crate) use legacy_form_pytest_raises::*;
 pub(crate) use logging_eager_conversion::*;
 pub(crate) use map_int_version_parsing::*;
@@ -46,6 +47,7 @@ pub(crate) use starmap_zip::*;
 pub(crate) use static_key_dict_comprehension::*;
 #[cfg(any(feature = "test-rules", test))]
 pub(crate) use test_rules::*;
+pub(crate) use unmatched_suppression_comment::*;
 pub(crate) use unnecessary_cast_to_int::*;
 pub(crate) use unnecessary_iterable_allocation_for_first_element::*;
 pub(crate) use unnecessary_key_check::*;
@@ -87,6 +89,7 @@ mod invalid_formatter_suppression_comment;
 mod invalid_index_type;
 mod invalid_pyproject_toml;
 mod invalid_rule_code;
+mod invalid_suppression_comment;
 mod legacy_form_pytest_raises;
 mod logging_eager_conversion;
 mod map_int_version_parsing;
@@ -113,6 +116,7 @@ mod static_key_dict_comprehension;
 mod suppression_comment_visitor;
 #[cfg(any(feature = "test-rules", test))]
 pub(crate) mod test_rules;
+mod unmatched_suppression_comment;
 mod unnecessary_cast_to_int;
 mod unnecessary_iterable_allocation_for_first_element;
 mod unnecessary_key_check;

crates/ruff_linter/src/rules/ruff/rules/unmatched_suppression_comment.rs

@@ -0,0 +1,42 @@
+use ruff_macros::{ViolationMetadata, derive_message_formats};
+
+use crate::Violation;
+
+/// ## What it does
+/// Checks for unmatched range suppression comments
+///
+/// ## Why is this bad?
+/// Unmatched range suppression comments can inadvertently suppress violations
+/// over larger sections of code than intended, particularly at module scope.
+///
+/// ## Example
+/// ```python
+/// def foo():
+///     # ruff: disable[E501]  # unmatched
+///     REALLY_LONG_VALUES = [...]
+///
+///     print(REALLY_LONG_VALUES)
+/// ```
+///
+/// Use instead:
+/// ```python
+/// def foo():
+///     # ruff: disable[E501]
+///     REALLY_LONG_VALUES = [...]
+///     # ruff: enable[E501]
+///
+///     print(REALLY_LONG_VALUES)
+/// ```
+///
+/// ## References
+/// - [Ruff error suppression](https://docs.astral.sh/ruff/linter/#error-suppression)
+#[derive(ViolationMetadata)]
+#[violation_metadata(preview_since = "0.14.11")]
+pub(crate) struct UnmatchedSuppressionComment;
+
+impl Violation for UnmatchedSuppressionComment {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        "Suppression comment without matching `#ruff:enable` comment".to_string()
+    }
+}

crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__range_suppressions.snap

@@ -6,8 +6,8 @@ source: crates/ruff_linter/src/rules/ruff/mod.rs
 +linter.preview = enabled
 
 --- Summary ---
-Removed: 14
-Added: 11
+Removed: 15
+Added: 23
 
 --- Removed ---
 E741 Ambiguous variable name: `I`
@@ -238,8 +238,60 @@ help: Remove assignment to unused variable `I`
 note: This is an unsafe fix and may change runtime behavior
 
 
+F841 [*] Local variable `value` is assigned to but never used
+  --> suppressions.py:95:5
+   |
+93 |     # ruff: disable[YF829]
+94 |     # ruff: disable[F841, RQW320]
+95 |     value = 0
+   |     ^^^^^
+96 |     # ruff: enable[F841, RQW320]
+97 |     # ruff: enable[YF829]
+   |
+help: Remove assignment to unused variable `value`
+92 |     # Unknown rule codes
+93 |     # ruff: disable[YF829]
+94 |     # ruff: disable[F841, RQW320]
+   -     value = 0
+95 +     pass
+96 |     # ruff: enable[F841, RQW320]
+97 |     # ruff: enable[YF829]
+98 | 
+note: This is an unsafe fix and may change runtime behavior
+
+
 
 --- Added ---
+RUF104 Suppression comment without matching `#ruff:enable` comment
+  --> suppressions.py:11:5
+   |
+ 9 |     # These should both be ignored by the implicit range suppression.
+10 |     # Should also generate an "unmatched suppression" warning.
+11 |     # ruff:disable[E741,F841]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+12 |     I = 1
+   |
+
+
+RUF103 [*] Invalid suppression comment: no matching 'disable' comment
+  --> suppressions.py:19:5
+   |
+17 |     # should be generated.
+18 |     I = 1
+19 |     # ruff: enable[E741, F841]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: Remove suppression comment
+16 |     # Neither warning is ignored, and an "unmatched suppression"
+17 |     # should be generated.
+18 |     I = 1
+   -     # ruff: enable[E741, F841]
+19 | 
+20 | 
+21 | def f():
+note: This is an unsafe fix and may change runtime behavior
+
+
 RUF100 [*] Unused suppression (non-enabled: `E501`)
   --> suppressions.py:46:5
    |
@@ -298,6 +350,17 @@ help: Remove unused `noqa` directive
 58 | 
 
 
+RUF104 Suppression comment without matching `#ruff:enable` comment
+  --> suppressions.py:61:5
+   |
+59 | def f():
+60 |     # TODO: Duplicate codes should be counted as duplicate, not unused
+61 |     # ruff: disable[F841, F841]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+62 |     foo = 0
+   |
+
+
 RUF100 [*] Unused suppression (unused: `F841`)
   --> suppressions.py:61:21
    |
@@ -318,6 +381,18 @@ help: Remove unused suppression
 64 | 
 
 
+RUF104 Suppression comment without matching `#ruff:enable` comment
+  --> suppressions.py:68:5
+   |
+66 |     # Overlapping range suppressions, one should be marked as used,
+67 |     # and the other should trigger an unused suppression diagnostic
+68 |     # ruff: disable[F841]
+   |     ^^^^^^^^^^^^^^^^^^^^^
+69 |     # ruff: disable[F841]
+70 |     foo = 0
+   |
+
+
 RUF100 [*] Unused suppression (unused: `F841`)
   --> suppressions.py:69:5
    |
@@ -337,6 +412,17 @@ help: Remove unused suppression
 71 | 
 
 
+RUF104 Suppression comment without matching `#ruff:enable` comment
+  --> suppressions.py:75:5
+   |
+73 | def f():
+74 |     # Multiple codes but only one is used
+75 |     # ruff: disable[E741, F401, F841]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+76 |     foo = 0
+   |
+
+
 RUF100 [*] Unused suppression (unused: `E741`)
   --> suppressions.py:75:21
    |
@@ -377,6 +463,17 @@ help: Remove unused suppression
 78 | 
 
 
+RUF104 Suppression comment without matching `#ruff:enable` comment
+  --> suppressions.py:81:5
+   |
+79 | def f():
+80 |     # Multiple codes but only two are used
+81 |     # ruff: disable[E741, F401, F841]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+82 |     I = 0
+   |
+
+
 RUF100 [*] Unused suppression (non-enabled: `F401`)
   --> suppressions.py:81:27
    |
@@ -413,6 +510,8 @@ help: Remove unused suppression
    -     # ruff: disable[E741, F401, F841]
 87 +     # ruff: disable[F401, F841]
 88 |     print("hello")
+89 | 
+90 | 
 
 
 RUF100 [*] Unused suppression (non-enabled: `F401`)
@@ -431,6 +530,8 @@ help: Remove unused suppression
    -     # ruff: disable[E741, F401, F841]
 87 +     # ruff: disable[E741, F841]
 88 |     print("hello")
+89 | 
+90 | 
 
 
 RUF100 [*] Unused suppression (unused: `F841`)
@@ -449,3 +550,122 @@ help: Remove unused suppression
    -     # ruff: disable[E741, F401, F841]
 87 +     # ruff: disable[E741, F401]
 88 |     print("hello")
+89 | 
+90 | 
+
+
+RUF102 [*] Invalid rule code in suppression: YF829
+  --> suppressions.py:93:21
+   |
+91 | def f():
+92 |     # Unknown rule codes
+93 |     # ruff: disable[YF829]
+   |                     ^^^^^
+94 |     # ruff: disable[F841, RQW320]
+95 |     value = 0
+   |
+help: Remove the rule code
+90 | 
+91 | def f():
+92 |     # Unknown rule codes
+   -     # ruff: disable[YF829]
+93 |     # ruff: disable[F841, RQW320]
+94 |     value = 0
+95 |     # ruff: enable[F841, RQW320]
+
+
+RUF102 [*] Invalid rule code in suppression: RQW320
+  --> suppressions.py:94:27
+   |
+92 |     # Unknown rule codes
+93 |     # ruff: disable[YF829]
+94 |     # ruff: disable[F841, RQW320]
+   |                           ^^^^^^
+95 |     value = 0
+96 |     # ruff: enable[F841, RQW320]
+   |
+help: Remove the rule code
+91 | def f():
+92 |     # Unknown rule codes
+93 |     # ruff: disable[YF829]
+   -     # ruff: disable[F841, RQW320]
+94 +     # ruff: disable[F841]
+95 |     value = 0
+96 |     # ruff: enable[F841, RQW320]
+97 |     # ruff: enable[YF829]
+
+
+RUF102 [*] Invalid rule code in suppression: RQW320
+  --> suppressions.py:96:26
+   |
+94 |     # ruff: disable[F841, RQW320]
+95 |     value = 0
+96 |     # ruff: enable[F841, RQW320]
+   |                          ^^^^^^
+97 |     # ruff: enable[YF829]
+   |
+help: Remove the rule code
+93 |     # ruff: disable[YF829]
+94 |     # ruff: disable[F841, RQW320]
+95 |     value = 0
+   -     # ruff: enable[F841, RQW320]
+96 +     # ruff: enable[F841]
+97 |     # ruff: enable[YF829]
+98 | 
+99 | 
+
+
+RUF102 [*] Invalid rule code in suppression: YF829
+  --> suppressions.py:97:20
+   |
+95 |     value = 0
+96 |     # ruff: enable[F841, RQW320]
+97 |     # ruff: enable[YF829]
+   |                    ^^^^^
+   |
+help: Remove the rule code
+94 |     # ruff: disable[F841, RQW320]
+95 |     value = 0
+96 |     # ruff: enable[F841, RQW320]
+   -     # ruff: enable[YF829]
+97 | 
+98 | 
+99 | def f():
+
+
+RUF103 [*] Invalid suppression comment: missing suppression codes like `[E501, ...]`
+   --> suppressions.py:109:5
+    |
+107 | def f():
+108 |     # Empty or missing rule codes
+109 |     # ruff: disable
+    |     ^^^^^^^^^^^^^^^
+110 |     # ruff: disable[]
+111 |     print("hello")
+    |
+help: Remove suppression comment
+106 | 
+107 | def f():
+108 |     # Empty or missing rule codes
+    -     # ruff: disable
+109 |     # ruff: disable[]
+110 |     print("hello")
+note: This is an unsafe fix and may change runtime behavior
+
+
+RUF103 [*] Invalid suppression comment: missing suppression codes like `[E501, ...]`
+   --> suppressions.py:110:5
+    |
+108 |     # Empty or missing rule codes
+109 |     # ruff: disable
+110 |     # ruff: disable[]
+    |     ^^^^^^^^^^^^^^^^^
+111 |     print("hello")
+    |
+help: Remove suppression comment
+107 | def f():
+108 |     # Empty or missing rule codes
+109 |     # ruff: disable
+    -     # ruff: disable[]
+110 |     print("hello")
+note: This is an unsafe fix and may change runtime behavior

crates/ruff_linter/src/settings/mod.rs

@@ -471,6 +471,13 @@ impl LinterSettings {
         self
     }
 
+    #[must_use]
+    pub fn with_external_rules(mut self, rules: &[&str]) -> Self {
+        self.external
+            .extend(rules.iter().map(std::string::ToString::to_string));
+        self
+    }
+
     /// Resolve the [`TargetVersion`] to use for linting.
     ///
     /// This method respects the per-file version overrides in

crates/ruff_linter/src/snapshots/ruff_linter__linter__tests__semantic_syntax_error_annotated_global.py_3.14.snap

@@ -0,0 +1,74 @@
+---
+source: crates/ruff_linter/src/linter.rs
+---
+invalid-syntax: annotated name `a` can't be global
+ --> resources/test/fixtures/semantic_errors/annotated_global.py:4:5
+  |
+2 | def f1():
+3 |     global a
+4 |     a: str = "foo"  # error
+  |     ^
+5 |
+6 | b: int = 1
+  |
+
+invalid-syntax: annotated name `b` can't be global
+  --> resources/test/fixtures/semantic_errors/annotated_global.py:10:9
+   |
+ 8 |     def inner():
+ 9 |         global b
+10 |         b: str = "nested"  # error
+   |         ^
+11 |
+12 | c: int = 1
+   |
+
+invalid-syntax: annotated name `c` can't be global
+  --> resources/test/fixtures/semantic_errors/annotated_global.py:15:5
+   |
+13 | def f2():
+14 |     global c
+15 |     c: list[str] = []  # error
+   |     ^
+16 |
+17 | d: int = 1
+   |
+
+invalid-syntax: annotated name `d` can't be global
+  --> resources/test/fixtures/semantic_errors/annotated_global.py:20:5
+   |
+18 | def f3():
+19 |     global d
+20 |     d: str  # error
+   |     ^
+21 |
+22 | e: int = 1
+   |
+
+invalid-syntax: annotated name `g` can't be global
+  --> resources/test/fixtures/semantic_errors/annotated_global.py:29:1
+   |
+27 | f: int = 1  # okay
+28 |
+29 | g: int = 1
+   | ^
+30 | global g  # error
+   |
+
+invalid-syntax: annotated name `x` can't be global
+  --> resources/test/fixtures/semantic_errors/annotated_global.py:33:5
+   |
+32 | class C:
+33 |     x: str
+   |     ^
+34 |     global x  # error
+   |
+
+invalid-syntax: annotated name `x` can't be global
+  --> resources/test/fixtures/semantic_errors/annotated_global.py:38:5
+   |
+36 | class D:
+37 |     global x  # error
+38 |     x: str
+   |     ^
+   |

crates/ruff_linter/src/suppression.rs

@@ -4,6 +4,7 @@ use ruff_db::diagnostic::Diagnostic;
 use ruff_diagnostics::{Edit, Fix};
 use ruff_python_ast::token::{TokenKind, Tokens};
 use ruff_python_ast::whitespace::indentation;
+use rustc_hash::FxHashSet;
 use std::cell::Cell;
 use std::{error::Error, fmt::Formatter};
 use thiserror::Error;
@@ -17,7 +18,11 @@ use crate::checkers::ast::LintContext;
 use crate::codes::Rule;
 use crate::fix::edits::delete_comment;
 use crate::preview::is_range_suppressions_enabled;
-use crate::rules::ruff::rules::{UnusedCodes, UnusedNOQA, UnusedNOQAKind};
+use crate::rule_redirects::get_redirect_target;
+use crate::rules::ruff::rules::{
+    InvalidRuleCode, InvalidRuleCodeKind, InvalidSuppressionComment, InvalidSuppressionCommentKind,
+    UnmatchedSuppressionComment, UnusedCodes, UnusedNOQA, UnusedNOQAKind, code_is_valid,
+};
 use crate::settings::LinterSettings;
 
 #[derive(Clone, Debug, Eq, PartialEq)]
@@ -130,7 +135,7 @@ impl Suppressions {
     }
 
     pub(crate) fn is_empty(&self) -> bool {
-        self.valid.is_empty()
+        self.valid.is_empty() && self.invalid.is_empty() && self.errors.is_empty()
     }
 
     /// Check if a diagnostic is suppressed by any known range suppressions
@@ -150,7 +155,9 @@ impl Suppressions {
         };
 
         for suppression in &self.valid {
-            if *code == suppression.code.as_str() && suppression.range.contains_range(range) {
+            let suppression_code =
+                get_redirect_target(suppression.code.as_str()).unwrap_or(suppression.code.as_str());
+            if *code == suppression_code && suppression.range.contains_range(range) {
                 suppression.used.set(true);
                 return true;
             }
@@ -159,81 +166,140 @@ impl Suppressions {
     }
 
     pub(crate) fn check_suppressions(&self, context: &LintContext, locator: &Locator) {
-        if !context.any_rule_enabled(&[Rule::UnusedNOQA, Rule::InvalidRuleCode]) {
-            return;
-        }
-
-        let unused = self
-            .valid
-            .iter()
-            .filter(|suppression| !suppression.used.get());
-
-        for suppression in unused {
-            let Ok(rule) = Rule::from_code(&suppression.code) else {
-                continue; // TODO: invalid code
-            };
-            for comment in &suppression.comments {
-                let mut range = comment.range;
-                let edit = if comment.codes.len() == 1 {
-                    delete_comment(comment.range, locator)
-                } else {
-                    let code_index = comment
-                        .codes
-                        .iter()
-                        .position(|range| locator.slice(range) == suppression.code)
-                        .unwrap();
-                    range = comment.codes[code_index];
-                    let code_range = if code_index < (comment.codes.len() - 1) {
-                        TextRange::new(
-                            comment.codes[code_index].start(),
-                            comment.codes[code_index + 1].start(),
-                        )
-                    } else {
-                        TextRange::new(
-                            comment.codes[code_index - 1].end(),
-                            comment.codes[code_index].end(),
-                        )
+        let mut unmatched_ranges = FxHashSet::default();
+        for suppression in &self.valid {
+            if !code_is_valid(&suppression.code, &context.settings().external) {
+                // InvalidRuleCode
+                if context.is_rule_enabled(Rule::InvalidRuleCode) {
+                    for comment in &suppression.comments {
+                        let (range, edit) = Suppressions::delete_code_or_comment(
+                            locator,
+                            suppression,
+                            comment,
+                            true,
+                        );
+                        context
+                            .report_diagnostic(
+                                InvalidRuleCode {
+                                    rule_code: suppression.code.to_string(),
+                                    kind: InvalidRuleCodeKind::Suppression,
+                                },
+                                range,
+                            )
+                            .set_fix(Fix::safe_edit(edit));
+                    }
+                }
+            } else if !suppression.used.get() {
+                // UnusedNOQA
+                if context.is_rule_enabled(Rule::UnusedNOQA) {
+                    let Ok(rule) = Rule::from_code(
+                        get_redirect_target(&suppression.code).unwrap_or(&suppression.code),
+                    ) else {
+                        continue; // "external" lint code, don't treat it as unused
                     };
-                    Edit::range_deletion(code_range)
-                };
+                    for comment in &suppression.comments {
+                        let (range, edit) = Suppressions::delete_code_or_comment(
+                            locator,
+                            suppression,
+                            comment,
+                            false,
+                        );
 
-                let codes = if context.is_rule_enabled(rule) {
-                    UnusedCodes {
-                        unmatched: vec![suppression.code.to_string()],
-                        ..Default::default()
-                    }
-                } else {
-                    UnusedCodes {
-                        disabled: vec![suppression.code.to_string()],
-                        ..Default::default()
-                    }
-                };
+                        let codes = if context.is_rule_enabled(rule) {
+                            UnusedCodes {
+                                unmatched: vec![suppression.code.to_string()],
+                                ..Default::default()
+                            }
+                        } else {
+                            UnusedCodes {
+                                disabled: vec![suppression.code.to_string()],
+                                ..Default::default()
+                            }
+                        };
 
-                let mut diagnostic = context.report_diagnostic(
-                    UnusedNOQA {
-                        codes: Some(codes),
-                        kind: UnusedNOQAKind::Suppression,
-                    },
-                    range,
-                );
-                diagnostic.set_fix(Fix::safe_edit(edit));
+                        context
+                            .report_diagnostic(
+                                UnusedNOQA {
+                                    codes: Some(codes),
+                                    kind: UnusedNOQAKind::Suppression,
+                                },
+                                range,
+                            )
+                            .set_fix(Fix::safe_edit(edit));
+                    }
+                }
+            } else if suppression.comments.len() == 1 {
+                // UnmatchedSuppressionComment
+                let range = suppression.comments[0].range;
+                if unmatched_ranges.insert(range) {
+                    context.report_diagnostic_if_enabled(UnmatchedSuppressionComment {}, range);
+                }
             }
         }
 
-        for error in self
-            .errors
-            .iter()
-            .filter(|error| error.kind == ParseErrorKind::MissingCodes)
-        {
-            let mut diagnostic = context.report_diagnostic(
-                UnusedNOQA {
-                    codes: Some(UnusedCodes::default()),
-                    kind: UnusedNOQAKind::Suppression,
-                },
-                error.range,
-            );
-            diagnostic.set_fix(Fix::safe_edit(delete_comment(error.range, locator)));
+        if context.is_rule_enabled(Rule::InvalidSuppressionComment) {
+            for error in &self.errors {
+                context
+                    .report_diagnostic(
+                        InvalidSuppressionComment {
+                            kind: InvalidSuppressionCommentKind::Error(error.kind),
+                        },
+                        error.range,
+                    )
+                    .set_fix(Fix::unsafe_edit(delete_comment(error.range, locator)));
+            }
         }
+
+        if context.is_rule_enabled(Rule::InvalidSuppressionComment) {
+            for invalid in &self.invalid {
+                context
+                    .report_diagnostic(
+                        InvalidSuppressionComment {
+                            kind: InvalidSuppressionCommentKind::Invalid(invalid.kind),
+                        },
+                        invalid.comment.range,
+                    )
+                    .set_fix(Fix::unsafe_edit(delete_comment(
+                        invalid.comment.range,
+                        locator,
+                    )));
+            }
+        }
+    }
+
+    fn delete_code_or_comment(
+        locator: &Locator<'_>,
+        suppression: &Suppression,
+        comment: &SuppressionComment,
+        highlight_only_code: bool,
+    ) -> (TextRange, Edit) {
+        let mut range = comment.range;
+        let edit = if comment.codes.len() == 1 {
+            if highlight_only_code {
+                range = comment.codes[0];
+            }
+            delete_comment(comment.range, locator)
+        } else {
+            let code_index = comment
+                .codes
+                .iter()
+                .position(|range| locator.slice(range) == suppression.code)
+                .unwrap();
+            range = comment.codes[code_index];
+            let code_range = if code_index < (comment.codes.len() - 1) {
+                TextRange::new(
+                    comment.codes[code_index].start(),
+                    comment.codes[code_index + 1].start(),
+                )
+            } else {
+                TextRange::new(
+                    comment.codes[code_index - 1].end(),
+                    comment.codes[code_index].end(),
+                )
+            };
+            Edit::range_deletion(code_range)
+        };
+        (range, edit)
     }
 }
 
@@ -391,7 +457,7 @@ impl<'a> SuppressionsBuilder<'a> {
 }
 
 #[derive(Copy, Clone, Debug, Eq, Error, PartialEq)]
-enum ParseErrorKind {
+pub(crate) enum ParseErrorKind {
     #[error("not a suppression comment")]
     NotASuppression,
 
@@ -401,7 +467,7 @@ enum ParseErrorKind {
     #[error("unknown ruff directive")]
     UnknownAction,
 
-    #[error("missing suppression codes")]
+    #[error("missing suppression codes like `[E501, ...]`")]
     MissingCodes,
 
     #[error("missing closing bracket")]

crates/ruff_python_ast/src/find_node.rs

@@ -1,5 +1,5 @@
-use ruff_python_ast::AnyNodeRef;
-use ruff_python_ast::visitor::source_order::{SourceOrderVisitor, TraversalSignal};
+use crate::AnyNodeRef;
+use crate::visitor::source_order::{SourceOrderVisitor, TraversalSignal, walk_node};
 use ruff_text_size::{Ranged, TextRange};
 use std::fmt;
 use std::fmt::Formatter;
@@ -11,7 +11,7 @@ use std::fmt::Formatter;
 ///
 /// ## Panics
 /// Panics if `range` is not contained within `root`.
-pub(crate) fn covering_node(root: AnyNodeRef, range: TextRange) -> CoveringNode {
+pub fn covering_node(root: AnyNodeRef, range: TextRange) -> CoveringNode {
     struct Visitor<'a> {
         range: TextRange,
         found: bool,
@@ -48,15 +48,12 @@ pub(crate) fn covering_node(root: AnyNodeRef, range: TextRange) -> CoveringNode
         ancestors: Vec::new(),
     };
 
-    root.visit_source_order(&mut visitor);
-    if visitor.ancestors.is_empty() {
-        visitor.ancestors.push(root);
-    }
+    walk_node(&mut visitor, root);
     CoveringNode::from_ancestors(visitor.ancestors)
 }
 
 /// The node with a minimal range that fully contains the search range.
-pub(crate) struct CoveringNode<'a> {
+pub struct CoveringNode<'a> {
     /// The covering node, along with all of its ancestors up to the
     /// root. The root is always the first element and the covering
     /// node found is always the last node. This sequence is guaranteed
@@ -67,12 +64,12 @@ pub(crate) struct CoveringNode<'a> {
 impl<'a> CoveringNode<'a> {
     /// Creates a new `CoveringNode` from a list of ancestor nodes.
     /// The ancestors should be ordered from root to the covering node.
-    pub(crate) fn from_ancestors(ancestors: Vec<AnyNodeRef<'a>>) -> Self {
+    pub fn from_ancestors(ancestors: Vec<AnyNodeRef<'a>>) -> Self {
         Self { nodes: ancestors }
     }
 
     /// Returns the covering node found.
-    pub(crate) fn node(&self) -> AnyNodeRef<'a> {
+    pub fn node(&self) -> AnyNodeRef<'a> {
         *self
             .nodes
             .last()
@@ -80,7 +77,7 @@ impl<'a> CoveringNode<'a> {
     }
 
     /// Returns the node's parent.
-    pub(crate) fn parent(&self) -> Option<AnyNodeRef<'a>> {
+    pub fn parent(&self) -> Option<AnyNodeRef<'a>> {
         let penultimate = self.nodes.len().checked_sub(2)?;
         self.nodes.get(penultimate).copied()
     }
@@ -90,7 +87,7 @@ impl<'a> CoveringNode<'a> {
     ///
     /// The "first" here means that the node closest to a leaf is
     /// returned.
-    pub(crate) fn find_first(mut self, f: impl Fn(AnyNodeRef<'a>) -> bool) -> Result<Self, Self> {
+    pub fn find_first(mut self, f: impl Fn(AnyNodeRef<'a>) -> bool) -> Result<Self, Self> {
         let Some(index) = self.find_first_index(f) else {
             return Err(self);
         };
@@ -105,7 +102,7 @@ impl<'a> CoveringNode<'a> {
     /// the highest ancestor found satisfying the given predicate is
     /// returned. Note that this is *not* the same as finding the node
     /// closest to the root that satisfies the given predictate.
-    pub(crate) fn find_last(mut self, f: impl Fn(AnyNodeRef<'a>) -> bool) -> Result<Self, Self> {
+    pub fn find_last(mut self, f: impl Fn(AnyNodeRef<'a>) -> bool) -> Result<Self, Self> {
         let Some(mut index) = self.find_first_index(&f) else {
             return Err(self);
         };
@@ -118,7 +115,7 @@ impl<'a> CoveringNode<'a> {
 
     /// Returns an iterator over the ancestor nodes, starting with the node itself
     /// and walking towards the root.
-    pub(crate) fn ancestors(&self) -> impl DoubleEndedIterator<Item = AnyNodeRef<'a>> + '_ {
+    pub fn ancestors(&self) -> impl DoubleEndedIterator<Item = AnyNodeRef<'a>> + '_ {
         self.nodes.iter().copied().rev()
     }
 

crates/ruff_python_ast/src/lib.rs

@@ -12,6 +12,7 @@ pub use python_version::*;
 pub mod comparable;
 pub mod docstrings;
 mod expression;
+pub mod find_node;
 mod generated;
 pub mod helpers;
 pub mod identifier;

crates/ruff_python_ast/src/traversal.rs

@@ -2,18 +2,25 @@
 use crate::{self as ast, AnyNodeRef, ExceptHandler, Stmt};
 
 /// Given a [`Stmt`] and its parent, return the [`ast::Suite`] that contains the [`Stmt`].
-pub fn suite<'a>(stmt: &'a Stmt, parent: &'a Stmt) -> Option<EnclosingSuite<'a>> {
+pub fn suite<'a>(
+    stmt: impl Into<AnyNodeRef<'a>>,
+    parent: impl Into<AnyNodeRef<'a>>,
+) -> Option<EnclosingSuite<'a>> {
     // TODO: refactor this to work without a parent, ie when `stmt` is at the top level
-    match parent {
-        Stmt::FunctionDef(ast::StmtFunctionDef { body, .. }) => EnclosingSuite::new(body, stmt),
-        Stmt::ClassDef(ast::StmtClassDef { body, .. }) => EnclosingSuite::new(body, stmt),
-        Stmt::For(ast::StmtFor { body, orelse, .. }) => [body, orelse]
+    let stmt = stmt.into();
+    match parent.into() {
+        AnyNodeRef::ModModule(ast::ModModule { body, .. }) => EnclosingSuite::new(body, stmt),
+        AnyNodeRef::StmtFunctionDef(ast::StmtFunctionDef { body, .. }) => {
+            EnclosingSuite::new(body, stmt)
+        }
+        AnyNodeRef::StmtClassDef(ast::StmtClassDef { body, .. }) => EnclosingSuite::new(body, stmt),
+        AnyNodeRef::StmtFor(ast::StmtFor { body, orelse, .. }) => [body, orelse]
             .iter()
             .find_map(|suite| EnclosingSuite::new(suite, stmt)),
-        Stmt::While(ast::StmtWhile { body, orelse, .. }) => [body, orelse]
+        AnyNodeRef::StmtWhile(ast::StmtWhile { body, orelse, .. }) => [body, orelse]
             .iter()
             .find_map(|suite| EnclosingSuite::new(suite, stmt)),
-        Stmt::If(ast::StmtIf {
+        AnyNodeRef::StmtIf(ast::StmtIf {
             body,
             elif_else_clauses,
             ..
@@ -21,12 +28,12 @@ pub fn suite<'a>(stmt: &'a Stmt, parent: &'a Stmt) -> Option<EnclosingSuite<'a>>
             .into_iter()
             .chain(elif_else_clauses.iter().map(|clause| &clause.body))
             .find_map(|suite| EnclosingSuite::new(suite, stmt)),
-        Stmt::With(ast::StmtWith { body, .. }) => EnclosingSuite::new(body, stmt),
-        Stmt::Match(ast::StmtMatch { cases, .. }) => cases
+        AnyNodeRef::StmtWith(ast::StmtWith { body, .. }) => EnclosingSuite::new(body, stmt),
+        AnyNodeRef::StmtMatch(ast::StmtMatch { cases, .. }) => cases
             .iter()
             .map(|case| &case.body)
             .find_map(|body| EnclosingSuite::new(body, stmt)),
-        Stmt::Try(ast::StmtTry {
+        AnyNodeRef::StmtTry(ast::StmtTry {
             body,
             handlers,
             orelse,
@@ -51,10 +58,10 @@ pub struct EnclosingSuite<'a> {
 }
 
 impl<'a> EnclosingSuite<'a> {
-    pub fn new(suite: &'a [Stmt], stmt: &'a Stmt) -> Option<Self> {
+    pub fn new(suite: &'a [Stmt], stmt: AnyNodeRef<'a>) -> Option<Self> {
         let position = suite
             .iter()
-            .position(|sibling| AnyNodeRef::ptr_eq(sibling.into(), stmt.into()))?;
+            .position(|sibling| AnyNodeRef::ptr_eq(sibling.into(), stmt))?;
 
         Some(EnclosingSuite { suite, position })
     }

crates/ruff_python_ast/src/visitor/source_order.rs

@@ -222,6 +222,17 @@ where
     visitor.leave_node(node);
 }
 
+pub fn walk_node<'a, V>(visitor: &mut V, node: AnyNodeRef<'a>)
+where
+    V: SourceOrderVisitor<'a> + ?Sized,
+{
+    if visitor.enter_node(node).is_traverse() {
+        node.visit_source_order(visitor);
+    }
+
+    visitor.leave_node(node);
+}
+
 #[derive(Copy, Clone, Eq, PartialEq, Debug)]
 pub enum TraversalSignal {
     Traverse,

crates/ruff_python_parser/src/semantic_errors.rs

@@ -272,7 +272,9 @@ impl SemanticSyntaxChecker {
 
     fn check_annotation<Ctx: SemanticSyntaxContext>(stmt: &ast::Stmt, ctx: &Ctx) {
         match stmt {
-            Stmt::AnnAssign(ast::StmtAnnAssign { annotation, .. }) => {
+            Stmt::AnnAssign(ast::StmtAnnAssign {
+                target, annotation, ..
+            }) => {
                 if ctx.python_version() > PythonVersion::PY313 {
                     // test_ok valid_annotation_py313
                     // # parse_options: {"target-version": "3.13"}
@@ -297,6 +299,18 @@ impl SemanticSyntaxChecker {
                     };
                     visitor.visit_expr(annotation);
                 }
+                if let Expr::Name(ast::ExprName { id, .. }) = target.as_ref() {
+                    if let Some(global_stmt) = ctx.global(id.as_str()) {
+                        let global_start = global_stmt.start();
+                        if !ctx.in_module_scope() || target.start() < global_start {
+                            Self::add_error(
+                                ctx,
+                                SemanticSyntaxErrorKind::AnnotatedGlobal(id.to_string()),
+                                target.range(),
+                            );
+                        }
+                    }
+                }
             }
             Stmt::FunctionDef(ast::StmtFunctionDef {
                 type_params,

crates/ruff_source_file/src/line_index.rs

@@ -179,42 +179,45 @@ impl LineIndex {
         let line = self.line_index(offset);
         let line_start = self.line_start(line, text);
 
+        let character_offset =
+            self.characters_between(TextRange::new(line_start, offset), text, encoding);
+
+        SourceLocation {
+            line,
+            character_offset: OneIndexed::from_zero_indexed(character_offset),
+        }
+    }
+
+    fn characters_between(
+        &self,
+        range: TextRange,
+        text: &str,
+        encoding: PositionEncoding,
+    ) -> usize {
         if self.is_ascii() {
-            return SourceLocation {
-                line,
-                character_offset: OneIndexed::from_zero_indexed((offset - line_start).to_usize()),
-            };
+            return (range.end() - range.start()).to_usize();
         }
 
         match encoding {
-            PositionEncoding::Utf8 => {
-                let character_offset = offset - line_start;
-                SourceLocation {
-                    line,
-                    character_offset: OneIndexed::from_zero_indexed(character_offset.to_usize()),
-                }
-            }
+            PositionEncoding::Utf8 => (range.end() - range.start()).to_usize(),
             PositionEncoding::Utf16 => {
-                let up_to_character = &text[TextRange::new(line_start, offset)];
-                let character = up_to_character.encode_utf16().count();
-
-                SourceLocation {
-                    line,
-                    character_offset: OneIndexed::from_zero_indexed(character),
-                }
+                let up_to_character = &text[range];
+                up_to_character.encode_utf16().count()
             }
             PositionEncoding::Utf32 => {
-                let up_to_character = &text[TextRange::new(line_start, offset)];
-                let character = up_to_character.chars().count();
-
-                SourceLocation {
-                    line,
-                    character_offset: OneIndexed::from_zero_indexed(character),
-                }
+                let up_to_character = &text[range];
+                up_to_character.chars().count()
             }
         }
     }
 
+    /// Returns the length of the line in characters, respecting the given encoding
+    pub fn line_len(&self, line: OneIndexed, text: &str, encoding: PositionEncoding) -> usize {
+        let line_range = self.line_range(line, text);
+
+        self.characters_between(line_range, text, encoding)
+    }
+
     /// Return the number of lines in the source code.
     pub fn line_count(&self) -> usize {
         self.line_starts().len()

crates/ruff_wasm/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff_wasm"
-version = "0.14.9"
+version = "0.14.10"
 publish = false
 authors = { workspace = true }
 edition = { workspace = true }

crates/ty/docs/rules.md

@@ -2511,38 +2511,6 @@ class A:
 A()[0]  # TypeError: 'A' object is not subscriptable
 ```
 
-## `possibly-missing-import`
-
-<small>
-Default level: <a href="../rules.md#rule-levels" title="This lint has a default level of 'warn'."><code>warn</code></a> ·
-Added in <a href="https://github.com/astral-sh/ty/releases/tag/0.0.1-alpha.22">0.0.1-alpha.22</a> ·
-<a href="https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-missing-import" target="_blank">Related issues</a> ·
-<a href="https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1575" target="_blank">View source</a>
-</small>
-
-
-**What it does**
-
-Checks for imports of symbols that may be missing.
-
-**Why is this bad?**
-
-Importing a missing module or name will raise a `ModuleNotFoundError`
-or `ImportError` at runtime.
-
-**Examples**
-
-```python
-# module.py
-import datetime
-
-if datetime.date.today().weekday() != 6:
-    a = 1
-
-# main.py
-from module import a  # ImportError: cannot import name 'a' from 'module'
-```
-
 ## `redundant-cast`
 
 <small>
@@ -2778,6 +2746,38 @@ Dividing by zero raises a `ZeroDivisionError` at runtime.
 5 / 0
 ```
 
+## `possibly-missing-import`
+
+<small>
+Default level: <a href="../rules.md#rule-levels" title="This lint has a default level of 'ignore'."><code>ignore</code></a> ·
+Added in <a href="https://github.com/astral-sh/ty/releases/tag/0.0.1-alpha.22">0.0.1-alpha.22</a> ·
+<a href="https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20possibly-missing-import" target="_blank">Related issues</a> ·
+<a href="https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L1575" target="_blank">View source</a>
+</small>
+
+
+**What it does**
+
+Checks for imports of symbols that may be missing.
+
+**Why is this bad?**
+
+Importing a missing module or name will raise a `ModuleNotFoundError`
+or `ImportError` at runtime.
+
+**Examples**
+
+```python
+# module.py
+import datetime
+
+if datetime.date.today().weekday() != 6:
+    a = 1
+
+# main.py
+from module import a  # ImportError: cannot import name 'a' from 'module'
+```
+
 ## `possibly-unresolved-reference`
 
 <small>

crates/ty/tests/cli/python_environment.rs

@@ -2703,3 +2703,51 @@ fn pythonpath_multiple_dirs_is_respected() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+/// Test behavior when `VIRTUAL_ENV` is set but points to a non-existent path.
+#[test]
+fn missing_virtual_env() -> anyhow::Result<()> {
+    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 case = CliTest::with_files([
+        (
+            "project/test.py",
+            r#"
+            from package1 import WorkingVenv
+            "#,
+        ),
+        (
+            "project/.venv/pyvenv.cfg",
+            r#"
+home = ./
+
+            "#,
+        ),
+        (
+            working_venv_package1_path,
+            r#"
+            class WorkingVenv: ...
+            "#,
+        ),
+    ])?;
+
+    assert_cmd_snapshot!(case.command()
+        .current_dir(case.root().join("project"))
+        .env("VIRTUAL_ENV", case.root().join("nonexistent-venv")), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    ty failed
+      Cause: Failed to discover local Python environment
+      Cause: Invalid `VIRTUAL_ENV` environment variable `<temp_dir>/nonexistent-venv`: does not point to a directory on disk
+      Cause: No such file or directory (os error 2)
+    ");
+
+    Ok(())
+}

crates/ty_completion_eval/completion-evaluation-tasks.csv

@@ -15,7 +15,7 @@ import-deprioritizes-type_check_only,main.py,3,2
 import-deprioritizes-type_check_only,main.py,4,3
 import-keyword-completion,main.py,0,1
 internal-typeshed-hidden,main.py,0,2
-none-completion,main.py,0,2
+none-completion,main.py,0,1
 numpy-array,main.py,0,159
 numpy-array,main.py,1,1
 object-attr-instance-methods,main.py,0,1

crates/ty_ide/src/code_action.rs

@@ -1,7 +1,8 @@
-use crate::{completion, find_node::covering_node};
+use crate::completion;
 
 use ruff_db::{files::File, parsed::parsed_module};
 use ruff_diagnostics::Edit;
+use ruff_python_ast::find_node::covering_node;
 use ruff_text_size::TextRange;
 use ty_project::Db;
 use ty_python_semantic::create_suppression_fix;

crates/ty_ide/src/goto.rs

@@ -5,9 +5,9 @@ pub use crate::goto_type_definition::goto_type_definition;
 
 use std::borrow::Cow;
 
-use crate::find_node::covering_node;
 use crate::stub_mapping::StubMapper;
 use ruff_db::parsed::ParsedModuleRef;
+use ruff_python_ast::find_node::{CoveringNode, covering_node};
 use ruff_python_ast::token::{TokenKind, Tokens};
 use ruff_python_ast::{self as ast, AnyNodeRef};
 use ruff_text_size::{Ranged, TextRange, TextSize};
@@ -665,7 +665,7 @@ impl GotoTarget<'_> {
     /// Creates a `GotoTarget` from a `CoveringNode` and an offset within the node
     pub(crate) fn from_covering_node<'a>(
         model: &SemanticModel,
-        covering_node: &crate::find_node::CoveringNode<'a>,
+        covering_node: &CoveringNode<'a>,
         offset: TextSize,
         tokens: &Tokens,
     ) -> Option<GotoTarget<'a>> {

crates/ty_ide/src/goto_declaration.rs

@@ -386,6 +386,29 @@ FOO = 0
         ");
     }
 
+    #[test]
+    fn goto_declaration_from_import_rhs_is_module() {
+        let test = CursorTest::builder()
+            .source("lib/__init__.py", r#""#)
+            .source("lib/module.py", r#""#)
+            .source("main.py", r#"from lib import module<CURSOR>"#)
+            .build();
+
+        // Should resolve to the actual function definition, not the import statement
+        assert_snapshot!(test.goto_declaration(), @r"
+        info[goto-declaration]: Go to declaration
+         --> main.py:1:17
+          |
+        1 | from lib import module
+          |                 ^^^^^^ Clicking here
+          |
+        info: Found 1 declaration
+        --> lib/module.py:1:1
+         |
+         |
+        ");
+    }
+
     #[test]
     fn goto_declaration_from_import_as() {
         let test = CursorTest::builder()

crates/ty_ide/src/hover.rs

@@ -187,29 +187,42 @@ mod tests {
         let test = cursor_test(
             r#"
         a = 10
+        """This is the docs for this value
+
+        Wow these are good docs!
+        """
 
         a<CURSOR>
         "#,
         );
 
-        assert_snapshot!(test.hover(), @r"
+        assert_snapshot!(test.hover(), @r#"
         Literal[10]
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
         ---------------------------------------------
         ```python
         Literal[10]
         ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
         ---------------------------------------------
         info[hover]: Hovered content is
-         --> main.py:4:1
+         --> main.py:8:1
           |
-        2 | a = 10
-        3 |
-        4 | a
+        6 | """
+        7 |
+        8 | a
           | ^- Cursor offset
           | |
           | source
           |
-        ");
+        "#);
     }
 
     #[test]
@@ -703,6 +716,10 @@ mod tests {
 
             def __init__(a: int, b: str):
                 self.a = a
+                """This is the docs for this value
+
+                Wow these are good docs!
+                """
                 self.b: str = b
 
         foo = Foo()
@@ -718,10 +735,10 @@ mod tests {
         ```
         ---------------------------------------------
         info[hover]: Hovered content is
-          --> main.py:10:5
+          --> main.py:14:5
            |
-         9 | foo = Foo()
-        10 | foo.a
+        13 | foo = Foo()
+        14 | foo.a
            |     -
            |     |
            |     source
@@ -1183,13 +1200,13 @@ def ab(a: str): ...
             .build();
 
         assert_snapshot!(test.hover(), @r"
-        (a: int) -> Unknown
+        def ab(a: int) -> Unknown
         ---------------------------------------------
         the int overload
 
         ---------------------------------------------
         ```python
-        (a: int) -> Unknown
+        def ab(a: int) -> Unknown
         ```
         ---
         the int overload
@@ -1243,13 +1260,13 @@ def ab(a: str):
             .build();
 
         assert_snapshot!(test.hover(), @r#"
-        (a: str) -> Unknown
+        def ab(a: str) -> Unknown
         ---------------------------------------------
         the int overload
 
         ---------------------------------------------
         ```python
-        (a: str) -> Unknown
+        def ab(a: str) -> Unknown
         ```
         ---
         the int overload
@@ -1303,7 +1320,7 @@ def ab(a: int):
             .build();
 
         assert_snapshot!(test.hover(), @r"
-        (
+        def ab(
             a: int,
             b: int
         ) -> Unknown
@@ -1312,7 +1329,7 @@ def ab(a: int):
 
         ---------------------------------------------
         ```python
-        (
+        def ab(
             a: int,
             b: int
         ) -> Unknown
@@ -1369,13 +1386,13 @@ def ab(a: int):
             .build();
 
         assert_snapshot!(test.hover(), @r"
-        (a: int) -> Unknown
+        def ab(a: int) -> Unknown
         ---------------------------------------------
         the two arg overload
 
         ---------------------------------------------
         ```python
-        (a: int) -> Unknown
+        def ab(a: int) -> Unknown
         ```
         ---
         the two arg overload
@@ -1433,7 +1450,7 @@ def ab(a: int, *, c: int):
             .build();
 
         assert_snapshot!(test.hover(), @r"
-        (
+        def ab(
             a: int,
             *,
             b: int
@@ -1443,7 +1460,7 @@ def ab(a: int, *, c: int):
 
         ---------------------------------------------
         ```python
-        (
+        def ab(
             a: int,
             *,
             b: int
@@ -1505,7 +1522,7 @@ def ab(a: int, *, c: int):
             .build();
 
         assert_snapshot!(test.hover(), @r"
-        (
+        def ab(
             a: int,
             *,
             c: int
@@ -1515,7 +1532,7 @@ def ab(a: int, *, c: int):
 
         ---------------------------------------------
         ```python
-        (
+        def ab(
             a: int,
             *,
             c: int
@@ -1564,11 +1581,11 @@ def ab(a: int, *, c: int):
         );
 
         assert_snapshot!(test.hover(), @r#"
-        (
+        def foo(
             a: int,
             b
         ) -> Unknown
-        (
+        def foo(
             a: str,
             b
         ) -> Unknown
@@ -1577,11 +1594,11 @@ def ab(a: int, *, c: int):
 
         ---------------------------------------------
         ```python
-        (
+        def foo(
             a: int,
             b
         ) -> Unknown
-        (
+        def foo(
             a: str,
             b
         ) -> Unknown
@@ -1628,15 +1645,15 @@ def ab(a: int, *, c: int):
         );
 
         assert_snapshot!(test.hover(), @r#"
-        (a: int) -> Unknown
-        (a: str) -> Unknown
+        def foo(a: int) -> Unknown
+        def foo(a: str) -> Unknown
         ---------------------------------------------
         The first overload
 
         ---------------------------------------------
         ```python
-        (a: int) -> Unknown
-        (a: str) -> Unknown
+        def foo(a: int) -> Unknown
+        def foo(a: str) -> Unknown
         ```
         ---
         The first overload
@@ -2345,15 +2362,28 @@ def function():
         let test = cursor_test(
             r#"
             value<CURSOR> = 1
+            """This is the docs for this value
+
+            Wow these are good docs!
+            """
             "#,
         );
 
-        assert_snapshot!(test.hover(), @r"
+        assert_snapshot!(test.hover(), @r#"
         Literal[1]
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
         ---------------------------------------------
         ```python
         Literal[1]
         ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
         ---------------------------------------------
         info[hover]: Hovered content is
          --> main.py:2:1
@@ -2362,8 +2392,9 @@ def function():
           | ^^^^^- Cursor offset
           | |
           | source
+        3 | """This is the docs for this value
           |
-        ");
+        "#);
     }
 
     #[test]
@@ -2371,7 +2402,15 @@ def function():
         let test = cursor_test(
             r#"
             value = 1
+            """This is the docs for this value
+
+            Wow these are good docs!
+            """
             value<CURSOR> += 2
+            """Other docs???
+
+            Is this allowed???
+            """
             "#,
         );
 
@@ -2379,23 +2418,34 @@ def function():
         // Showing the new value might be more intuitive for some users, but the actual 'use'
         // of the `value` symbol here in read-context is `1`. This comment mainly exists to
         // signal that it might be okay to revisit this in the future and reveal 3 instead.
-        assert_snapshot!(test.hover(), @r"
+        assert_snapshot!(test.hover(), @r#"
         Literal[1]
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
         ---------------------------------------------
         ```python
         Literal[1]
         ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
         ---------------------------------------------
         info[hover]: Hovered content is
-         --> main.py:3:1
+         --> main.py:7:1
           |
-        2 | value = 1
-        3 | value += 2
+        5 | Wow these are good docs!
+        6 | """
+        7 | value += 2
           | ^^^^^- Cursor offset
           | |
           | source
+        8 | """Other docs???
           |
-        ");
+        "#);
     }
 
     #[test]
@@ -2404,29 +2454,47 @@ def function():
             r#"
             class C:
                 attr: int = 1
+                """This is the docs for this value
+
+                Wow these are good docs!
+                """
 
             C.attr<CURSOR> = 2
+            """Other docs???
+
+            Is this allowed???
+            """
             "#,
         );
 
-        assert_snapshot!(test.hover(), @r"
+        assert_snapshot!(test.hover(), @r#"
         Literal[2]
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
         ---------------------------------------------
         ```python
         Literal[2]
         ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
         ---------------------------------------------
         info[hover]: Hovered content is
-         --> main.py:5:3
-          |
-        3 |     attr: int = 1
-        4 |
-        5 | C.attr = 2
-          |   ^^^^- Cursor offset
-          |   |
-          |   source
-          |
-        ");
+          --> main.py:9:3
+           |
+         7 |     """
+         8 |
+         9 | C.attr = 2
+           |   ^^^^- Cursor offset
+           |   |
+           |   source
+        10 | """Other docs???
+           |
+        "#);
     }
 
     #[test]
@@ -2435,31 +2503,49 @@ def function():
             r#"
             class C:
                 attr = 1
+                """This is the docs for this value
+
+                Wow these are good docs!
+                """
 
             C.attr<CURSOR> += 2
+            """Other docs???
+
+            Is this allowed???
+            """
             "#,
         );
 
         // See the comment in the `hover_augmented_assignment` test above. The same
         // reasoning applies here.
-        assert_snapshot!(test.hover(), @r"
+        assert_snapshot!(test.hover(), @r#"
         Unknown | Literal[1]
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
         ---------------------------------------------
         ```python
         Unknown | Literal[1]
         ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
         ---------------------------------------------
         info[hover]: Hovered content is
-         --> main.py:5:3
-          |
-        3 |     attr = 1
-        4 |
-        5 | C.attr += 2
-          |   ^^^^- Cursor offset
-          |   |
-          |   source
-          |
-        ");
+          --> main.py:9:3
+           |
+         7 |     """
+         8 |
+         9 | C.attr += 2
+           |   ^^^^- Cursor offset
+           |   |
+           |   source
+        10 | """Other docs???
+           |
+        "#);
     }
 
     #[test]
@@ -2468,15 +2554,28 @@ def function():
             r#"
         class Foo:
             a<CURSOR>: int
+            """This is the docs for this value
+
+            Wow these are good docs!
+            """
         "#,
         );
 
-        assert_snapshot!(test.hover(), @r"
+        assert_snapshot!(test.hover(), @r#"
         int
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
         ---------------------------------------------
         ```python
         int
         ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
         ---------------------------------------------
         info[hover]: Hovered content is
          --> main.py:3:5
@@ -2486,8 +2585,9 @@ def function():
           |     ^- Cursor offset
           |     |
           |     source
+        4 |     """This is the docs for this value
           |
-        ");
+        "#);
     }
 
     #[test]
@@ -2496,15 +2596,28 @@ def function():
             r#"
         class Foo:
             a<CURSOR>: int = 1
+            """This is the docs for this value
+
+            Wow these are good docs!
+            """
         "#,
         );
 
-        assert_snapshot!(test.hover(), @r"
+        assert_snapshot!(test.hover(), @r#"
         Literal[1]
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
         ---------------------------------------------
         ```python
         Literal[1]
         ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
         ---------------------------------------------
         info[hover]: Hovered content is
          --> main.py:3:5
@@ -2514,7 +2627,52 @@ def function():
           |     ^- Cursor offset
           |     |
           |     source
+        4 |     """This is the docs for this value
           |
+        "#);
+    }
+
+    #[test]
+    fn hover_annotated_assignment_with_rhs_use() {
+        let test = cursor_test(
+            r#"
+        class Foo:
+            a: int = 1
+            """This is the docs for this value
+
+            Wow these are good docs!
+            """
+        
+        x = Foo()
+        x.a<CURSOR>
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @r"
+        int
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
+        ---------------------------------------------
+        ```python
+        int
+        ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
+        ---------------------------------------------
+        info[hover]: Hovered content is
+          --> main.py:10:3
+           |
+         9 | x = Foo()
+        10 | x.a
+           |   ^- Cursor offset
+           |   |
+           |   source
+           |
         ");
     }
 
@@ -2525,15 +2683,28 @@ def function():
         class Foo:
             def __init__(self, a: int):
                 self.a<CURSOR>: int = a
+                """This is the docs for this value
+
+                Wow these are good docs!
+                """
         "#,
         );
 
-        assert_snapshot!(test.hover(), @r"
+        assert_snapshot!(test.hover(), @r#"
         int
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
         ---------------------------------------------
         ```python
         int
         ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
         ---------------------------------------------
         info[hover]: Hovered content is
          --> main.py:4:14
@@ -2544,7 +2715,53 @@ def function():
           |              ^- Cursor offset
           |              |
           |              source
+        5 |         """This is the docs for this value
           |
+        "#);
+    }
+
+    #[test]
+    fn hover_annotated_attribute_assignment_use() {
+        let test = cursor_test(
+            r#"
+        class Foo:
+            def __init__(self, a: int):
+                self.a: int = a
+                """This is the docs for this value
+
+                Wow these are good docs!
+                """
+
+        x = Foo(1)
+        x.a<CURSOR>
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @r"
+        int
+        ---------------------------------------------
+        This is the docs for this value
+
+        Wow these are good docs!
+
+        ---------------------------------------------
+        ```python
+        int
+        ```
+        ---
+        This is the docs for this value  
+          
+        Wow these are good docs!
+        ---------------------------------------------
+        info[hover]: Hovered content is
+          --> main.py:11:3
+           |
+        10 | x = Foo(1)
+        11 | x.a
+           |   ^- Cursor offset
+           |   |
+           |   source
+           |
         ");
     }
 
@@ -3233,12 +3450,12 @@ def function():
         // TODO: We should only show the matching overload here.
         // https://github.com/astral-sh/ty/issues/73
         assert_snapshot!(test.hover(), @r"
-        (other: Test, /) -> Test
-        (other: Other, /) -> Test
+        def __add__(other: Test, /) -> Test
+        def __add__(other: Other, /) -> Test
         ---------------------------------------------
         ```python
-        (other: Test, /) -> Test
-        (other: Other, /) -> Test
+        def __add__(other: Test, /) -> Test
+        def __add__(other: Other, /) -> Test
         ```
         ---------------------------------------------
         info[hover]: Hovered content is

crates/ty_ide/src/importer.rs

@@ -869,7 +869,6 @@ mod tests {
     use insta::assert_snapshot;
     use insta::internals::SettingsBindDropGuard;
 
-    use crate::find_node::covering_node;
     use crate::tests::{CursorTest, CursorTestBuilder, cursor_test};
     use ruff_db::diagnostic::{Diagnostic, DiagnosticFormat, DisplayDiagnosticConfig};
     use ruff_db::files::{File, FileRootKind, system_path_to_file};
@@ -877,6 +876,7 @@ mod tests {
     use ruff_db::source::source_text;
     use ruff_db::system::{DbWithWritableSystem, SystemPath, SystemPathBuf};
     use ruff_db::{Db, system};
+    use ruff_python_ast::find_node::covering_node;
     use ruff_python_codegen::Stylist;
     use ruff_python_trivia::textwrap::dedent;
     use ruff_text_size::TextSize;

crates/ty_ide/src/lib.rs

@@ -8,7 +8,6 @@ mod completion;
 mod doc_highlights;
 mod docstring;
 mod document_symbols;
-mod find_node;
 mod find_references;
 mod goto;
 mod goto_declaration;

crates/ty_ide/src/references.rs

@@ -10,10 +10,10 @@
 //! all references to these externally-visible symbols therefore requires
 //! an expensive search of all source files in the workspace.
 
-use crate::find_node::CoveringNode;
 use crate::goto::GotoTarget;
 use crate::{Db, NavigationTargets, ReferenceKind, ReferenceTarget};
 use ruff_db::files::File;
+use ruff_python_ast::find_node::CoveringNode;
 use ruff_python_ast::token::Tokens;
 use ruff_python_ast::{
     self as ast, AnyNodeRef,
@@ -334,10 +334,7 @@ impl LocalReferencesFinder<'_> {
 
     /// Determines whether the given covering node is a reference to
     /// the symbol we are searching for
-    fn check_reference_from_covering_node(
-        &mut self,
-        covering_node: &crate::find_node::CoveringNode<'_>,
-    ) {
+    fn check_reference_from_covering_node(&mut self, covering_node: &CoveringNode<'_>) {
         // Use the start of the covering node as the offset. Any offset within
         // the node is fine here. Offsets matter only for import statements
         // where the identifier might be a multi-part module name.

crates/ty_ide/src/selection_range.rs

@@ -1,9 +1,9 @@
 use ruff_db::files::File;
 use ruff_db::parsed::parsed_module;
+use ruff_python_ast::find_node::covering_node;
 use ruff_text_size::{Ranged, TextRange, TextSize};
 
 use crate::Db;
-use crate::find_node::covering_node;
 
 /// Returns a list of nested selection ranges, where each range contains the next one.
 /// The first range in the list is the largest range containing the cursor position.
@@ -66,20 +66,28 @@ x = 1 + <CURSOR>2
 
         assert_snapshot!(test.selection_range(), @r"
         info[selection-range]: Selection Range 0
+         --> main.py:1:1
+          |
+        1 | /
+        2 | | x = 1 + 2
+          | |__________^
+          |
+
+        info[selection-range]: Selection Range 1
          --> main.py:2:1
           |
         2 | x = 1 + 2
           | ^^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 1
+        info[selection-range]: Selection Range 2
          --> main.py:2:5
           |
         2 | x = 1 + 2
           |     ^^^^^
           |
 
-        info[selection-range]: Selection Range 2
+        info[selection-range]: Selection Range 3
          --> main.py:2:9
           |
         2 | x = 1 + 2
@@ -102,20 +110,28 @@ print(\"he<CURSOR>llo\")
 
         assert_snapshot!(test.selection_range(), @r#"
         info[selection-range]: Selection Range 0
+         --> main.py:1:1
+          |
+        1 | /
+        2 | | print("hello")
+          | |_______________^
+          |
+
+        info[selection-range]: Selection Range 1
          --> main.py:2:1
           |
         2 | print("hello")
           | ^^^^^^^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 1
+        info[selection-range]: Selection Range 2
          --> main.py:2:6
           |
         2 | print("hello")
           |      ^^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 2
+        info[selection-range]: Selection Range 3
          --> main.py:2:7
           |
         2 | print("hello")
@@ -139,6 +155,15 @@ def my_<CURSOR>function():
 
         assert_snapshot!(test.selection_range(), @r"
         info[selection-range]: Selection Range 0
+         --> main.py:1:1
+          |
+        1 | /
+        2 | | def my_function():
+        3 | |     return 42
+          | |______________^
+          |
+
+        info[selection-range]: Selection Range 1
          --> main.py:2:1
           |
         2 | / def my_function():
@@ -146,7 +171,7 @@ def my_<CURSOR>function():
           | |_____________^
           |
 
-        info[selection-range]: Selection Range 1
+        info[selection-range]: Selection Range 2
          --> main.py:2:5
           |
         2 | def my_function():
@@ -172,6 +197,16 @@ class My<CURSOR>Class:
 
         assert_snapshot!(test.selection_range(), @r"
         info[selection-range]: Selection Range 0
+         --> main.py:1:1
+          |
+        1 | /
+        2 | | class MyClass:
+        3 | |     def __init__(self):
+        4 | |         self.value = 1
+          | |_______________________^
+          |
+
+        info[selection-range]: Selection Range 1
          --> main.py:2:1
           |
         2 | / class MyClass:
@@ -180,7 +215,7 @@ class My<CURSOR>Class:
           | |______________________^
           |
 
-        info[selection-range]: Selection Range 1
+        info[selection-range]: Selection Range 2
          --> main.py:2:7
           |
         2 | class MyClass:
@@ -205,48 +240,56 @@ result = [(lambda x: x[key.<CURSOR>attr])(item) for item in data if item is not
 
         assert_snapshot!(test.selection_range(), @r"
         info[selection-range]: Selection Range 0
+         --> main.py:1:1
+          |
+        1 | /
+        2 | | result = [(lambda x: x[key.attr])(item) for item in data if item is not None]
+          | |______________________________________________________________________________^
+          |
+
+        info[selection-range]: Selection Range 1
          --> main.py:2:1
           |
         2 | result = [(lambda x: x[key.attr])(item) for item in data if item is not None]
           | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 1
+        info[selection-range]: Selection Range 2
          --> main.py:2:10
           |
         2 | result = [(lambda x: x[key.attr])(item) for item in data if item is not None]
           |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 2
+        info[selection-range]: Selection Range 3
          --> main.py:2:11
           |
         2 | result = [(lambda x: x[key.attr])(item) for item in data if item is not None]
           |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 3
+        info[selection-range]: Selection Range 4
          --> main.py:2:12
           |
         2 | result = [(lambda x: x[key.attr])(item) for item in data if item is not None]
           |            ^^^^^^^^^^^^^^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 4
+        info[selection-range]: Selection Range 5
          --> main.py:2:22
           |
         2 | result = [(lambda x: x[key.attr])(item) for item in data if item is not None]
           |                      ^^^^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 5
+        info[selection-range]: Selection Range 6
          --> main.py:2:24
           |
         2 | result = [(lambda x: x[key.attr])(item) for item in data if item is not None]
           |                        ^^^^^^^^
           |
 
-        info[selection-range]: Selection Range 6
+        info[selection-range]: Selection Range 7
          --> main.py:2:28
           |
         2 | result = [(lambda x: x[key.attr])(item) for item in data if item is not None]

crates/ty_ide/src/signature_help.rs

@@ -6,11 +6,12 @@
 //! types, and documentation. It supports multiple signatures for union types
 //! and overloads.
 
+use crate::Db;
 use crate::docstring::Docstring;
 use crate::goto::Definitions;
-use crate::{Db, find_node::covering_node};
 use ruff_db::files::File;
 use ruff_db::parsed::parsed_module;
+use ruff_python_ast::find_node::covering_node;
 use ruff_python_ast::token::TokenKind;
 use ruff_python_ast::{self as ast, AnyNodeRef};
 use ruff_text_size::{Ranged, TextRange, TextSize};

crates/ty_project/src/metadata.rs

@@ -5,7 +5,7 @@ use ruff_python_ast::name::Name;
 use std::sync::Arc;
 use thiserror::Error;
 use ty_combine::Combine;
-use ty_python_semantic::ProgramSettings;
+use ty_python_semantic::{MisconfigurationMode, ProgramSettings};
 
 use crate::metadata::options::ProjectOptionsOverrides;
 use crate::metadata::pyproject::{Project, PyProject, PyProjectError, ResolveRequiresPythonError};
@@ -37,6 +37,9 @@ pub struct ProjectMetadata {
     /// The path ordering doesn't imply precedence.
     #[cfg_attr(test, serde(skip_serializing_if = "Vec::is_empty"))]
     pub(super) extra_configuration_paths: Vec<SystemPathBuf>,
+
+    #[cfg_attr(test, serde(skip))]
+    pub(super) misconfiguration_mode: MisconfigurationMode,
 }
 
 impl ProjectMetadata {
@@ -47,6 +50,7 @@ impl ProjectMetadata {
             root,
             extra_configuration_paths: Vec::default(),
             options: Options::default(),
+            misconfiguration_mode: MisconfigurationMode::Fail,
         }
     }
 
@@ -70,6 +74,7 @@ impl ProjectMetadata {
             root: system.current_directory().to_path_buf(),
             options,
             extra_configuration_paths: vec![path],
+            misconfiguration_mode: MisconfigurationMode::Fail,
         })
     }
 
@@ -82,6 +87,7 @@ impl ProjectMetadata {
             pyproject.tool.and_then(|tool| tool.ty).unwrap_or_default(),
             root,
             pyproject.project.as_ref(),
+            MisconfigurationMode::Fail,
         )
     }
 
@@ -90,6 +96,7 @@ impl ProjectMetadata {
         mut options: Options,
         root: SystemPathBuf,
         project: Option<&Project>,
+        misconfiguration_mode: MisconfigurationMode,
     ) -> Result<Self, ResolveRequiresPythonError> {
         let name = project
             .and_then(|project| project.name.as_deref())
@@ -117,6 +124,7 @@ impl ProjectMetadata {
             root,
             options,
             extra_configuration_paths: Vec::new(),
+            misconfiguration_mode,
         })
     }
 
@@ -194,6 +202,7 @@ impl ProjectMetadata {
                     pyproject
                         .as_ref()
                         .and_then(|pyproject| pyproject.project.as_ref()),
+                    MisconfigurationMode::Fail,
                 )
                 .map_err(|err| {
                     ProjectMetadataError::InvalidRequiresPythonConstraint {
@@ -273,8 +282,13 @@ impl ProjectMetadata {
         system: &dyn System,
         vendored: &VendoredFileSystem,
     ) -> anyhow::Result<ProgramSettings> {
-        self.options
-            .to_program_settings(self.root(), self.name(), system, vendored)
+        self.options.to_program_settings(
+            self.root(),
+            self.name(),
+            system,
+            vendored,
+            self.misconfiguration_mode,
+        )
     }
 
     pub fn apply_overrides(&mut self, overrides: &ProjectOptionsOverrides) {

crates/ty_project/src/metadata/options.rs

@@ -30,9 +30,9 @@ use thiserror::Error;
 use ty_combine::Combine;
 use ty_python_semantic::lint::{Level, LintSource, RuleSelection};
 use ty_python_semantic::{
-    ProgramSettings, PythonEnvironment, PythonPlatform, PythonVersionFileSource,
-    PythonVersionSource, PythonVersionWithSource, SearchPathSettings, SearchPathValidationError,
-    SearchPaths, SitePackagesPaths, SysPrefixPathOrigin,
+    MisconfigurationMode, ProgramSettings, PythonEnvironment, PythonPlatform,
+    PythonVersionFileSource, PythonVersionSource, PythonVersionWithSource, SearchPathSettings,
+    SearchPathValidationError, SearchPaths, SitePackagesPaths, SysPrefixPathOrigin,
 };
 use ty_static::EnvVars;
 
@@ -117,6 +117,7 @@ impl Options {
         project_name: &str,
         system: &dyn System,
         vendored: &VendoredFileSystem,
+        misconfiguration_mode: MisconfigurationMode,
     ) -> anyhow::Result<ProgramSettings> {
         let environment = self.environment.or_default();
 
@@ -154,14 +155,25 @@ impl Options {
                 ValueSource::Editor => SysPrefixPathOrigin::Editor,
             };
 
-            Some(PythonEnvironment::new(
-                python_path.absolute(project_root, system),
-                origin,
-                system,
-            )?)
+            PythonEnvironment::new(python_path.absolute(project_root, system), origin, system)
+                .map_err(anyhow::Error::from)
+                .map(Some)
         } else {
             PythonEnvironment::discover(project_root, system)
-                .context("Failed to discover local Python environment")?
+                .context("Failed to discover local Python environment")
+        };
+
+        // If in safe-mode, fallback to None if this fails instead of erroring.
+        let python_environment = match python_environment {
+            Ok(python_environment) => python_environment,
+            Err(err) => {
+                if misconfiguration_mode == MisconfigurationMode::UseDefault {
+                    tracing::debug!("Default settings failed to discover local Python environment");
+                    None
+                } else {
+                    return Err(err);
+                }
+            }
         };
 
         let self_site_packages = self_environment_search_paths(
@@ -174,11 +186,23 @@ impl Options {
         .unwrap_or_default();
 
         let site_packages_paths = if let Some(python_environment) = python_environment.as_ref() {
-            self_site_packages.concatenate(
-                python_environment
-                    .site_packages_paths(system)
-                    .context("Failed to discover the site-packages directory")?,
-            )
+            let site_packages_paths = python_environment
+                .site_packages_paths(system)
+                .context("Failed to discover the site-packages directory");
+            let site_packages_paths = match site_packages_paths {
+                Ok(paths) => paths,
+                Err(err) => {
+                    if misconfiguration_mode == MisconfigurationMode::UseDefault {
+                        tracing::debug!(
+                            "Default settings failed to discover site-packages directory"
+                        );
+                        SitePackagesPaths::default()
+                    } else {
+                        return Err(err);
+                    }
+                }
+            };
+            self_site_packages.concatenate(site_packages_paths)
         } else {
             tracing::debug!("No virtual environment found");
             self_site_packages
@@ -201,6 +225,7 @@ impl Options {
             .or_else(|| site_packages_paths.python_version_from_layout())
             .unwrap_or_default();
 
+        // Safe mode is handled inside this function, so we just assume this can't fail
         let search_paths = self.to_search_paths(
             project_root,
             project_name,
@@ -208,6 +233,7 @@ impl Options {
             real_stdlib_path,
             system,
             vendored,
+            misconfiguration_mode,
         )?;
 
         tracing::info!(
@@ -222,6 +248,7 @@ impl Options {
         })
     }
 
+    #[expect(clippy::too_many_arguments)]
     fn to_search_paths(
         &self,
         project_root: &SystemPath,
@@ -230,6 +257,7 @@ impl Options {
         real_stdlib_path: Option<SystemPathBuf>,
         system: &dyn System,
         vendored: &VendoredFileSystem,
+        misconfiguration_mode: MisconfigurationMode,
     ) -> Result<SearchPaths, SearchPathValidationError> {
         let environment = self.environment.or_default();
         let src = self.src.or_default();
@@ -344,6 +372,7 @@ impl Options {
                 .map(|path| path.absolute(project_root, system)),
             site_packages_paths: site_packages_paths.into_vec(),
             real_stdlib_path,
+            misconfiguration_mode,
         };
 
         settings.to_search_paths(system, vendored)

crates/ty_python_semantic/Cargo.toml

@@ -33,7 +33,7 @@ camino = { workspace = true }
 colored = { workspace = true }
 compact_str = { workspace = true }
 drop_bomb = { workspace = true }
-get-size2 = { workspace = true, features = ["indexmap", "ordermap"]}
+get-size2 = { workspace = true, features = ["indexmap", "ordermap"] }
 indexmap = { workspace = true }
 itertools = { workspace = true }
 ordermap = { workspace = true }
@@ -62,7 +62,7 @@ ty_test = { workspace = true }
 ty_vendored = { workspace = true }
 
 anyhow = { workspace = true }
-dir-test = { workspace = true }
+datatest-stable = { workspace = true }
 glob = { workspace = true }
 indoc = { workspace = true }
 insta = { workspace = true }
@@ -76,5 +76,9 @@ schemars = ["dep:schemars", "dep:serde_json"]
 serde = ["ruff_db/serde", "dep:serde", "ruff_python_ast/serde"]
 testing = []
 
+[[test]]
+name = "mdtest"
+harness = false
+
 [lints]
 workspace = true

crates/ty_python_semantic/build.rs

@@ -1,4 +0,0 @@
-/// Rebuild the crate if a test file is added or removed from
-pub fn main() {
-    println!("cargo::rerun-if-changed=resources/mdtest");
-}

crates/ty_python_semantic/mdtest.py

@@ -129,17 +129,8 @@ class MDTestRunner:
             check=False,
         )
 
-    def _mangle_path(self, markdown_file: Path) -> str:
-        return (
-            markdown_file.as_posix()
-            .replace("/", "_")
-            .replace("-", "_")
-            .removesuffix(".md")
-        )
-
     def _run_mdtests_for_file(self, markdown_file: Path) -> None:
-        path_mangled = self._mangle_path(markdown_file)
-        test_name = f"mdtest__{path_mangled}"
+        test_name = f"mdtest::{markdown_file}"
 
         output = self._run_mdtest(["--exact", test_name], capture_output=True)
 
@@ -245,16 +236,10 @@ class MDTestRunner:
             if rust_code_has_changed:
                 if self._recompile_tests("Rust code has changed, recompiling tests..."):
                     self._run_mdtest(self.filters)
-            elif vendored_typeshed_has_changed:
-                if self._recompile_tests(
-                    "Vendored typeshed has changed, recompiling tests..."
-                ):
-                    self._run_mdtest(self.filters)
-            elif new_md_files:
-                files = " ".join(file.as_posix() for file in new_md_files)
-                self._recompile_tests(
-                    f"New Markdown test [yellow]{files}[/yellow] detected, recompiling tests..."
-                )
+            elif vendored_typeshed_has_changed and self._recompile_tests(
+                "Vendored typeshed has changed, recompiling tests..."
+            ):
+                self._run_mdtest(self.filters)
 
             for path in new_md_files | changed_md_files:
                 self._run_mdtests_for_file(path)

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

@@ -205,3 +205,93 @@ class B:
 class A(B): ...
 class B: ...
 ```
+
+## Default argument values
+
+### Not deferred in regular files
+
+```py
+# error: [unresolved-reference]
+def f(mode: int = ParseMode.test):
+    pass
+
+class ParseMode:
+    test = 1
+```
+
+### Deferred in stub files
+
+Forward references in default argument values are allowed in stub files.
+
+```pyi
+def f(mode: int = ParseMode.test): ...
+
+class ParseMode:
+    test: int
+```
+
+### Undefined names are still errors in stub files
+
+```pyi
+# error: [unresolved-reference]
+def f(mode: int = NeverDefined.test): ...
+```
+
+## Class keyword arguments
+
+### Not deferred in regular files
+
+```py
+# error: [unresolved-reference]
+class Foo(metaclass=SomeMeta):
+    pass
+
+class SomeMeta(type):
+    pass
+```
+
+### Deferred in stub files
+
+Forward references in class keyword arguments are allowed in stub files.
+
+```pyi
+class Foo(metaclass=SomeMeta): ...
+
+class SomeMeta(type): ...
+```
+
+### Undefined names are still errors in stub files
+
+```pyi
+# error: [unresolved-reference]
+class Foo(metaclass=NeverDefined): ...
+```
+
+## Lambda default argument values
+
+### Not deferred in regular files
+
+```py
+# error: [unresolved-reference]
+f = lambda x=Foo(): x
+
+class Foo:
+    pass
+```
+
+### Deferred in stub files
+
+Forward references in lambda default argument values are allowed in stub files.
+
+```pyi
+f = lambda x=Foo(): x
+
+class Foo: ...
+```
+
+### Undefined names are still errors in stub files
+
+```pyi
+# error: [unresolved-reference]
+f = lambda x=NeverDefined(): x
+```

crates/ty_python_semantic/resources/mdtest/attributes.md

@@ -1208,7 +1208,7 @@ def _(flag: bool):
     reveal_type(C1.y)  # revealed: int | str
 
     C1.y = 100
-    # error: [invalid-assignment] "Object of type `Literal["problematic"]` is not assignable to attribute `y` on type `<class 'C1'> | <class 'C1'>`"
+    # error: [invalid-assignment] "Object of type `Literal["problematic"]` is not assignable to attribute `y` on type `<class 'mdtest_snippet.<locals of function '_'>.C1 @ src/mdtest_snippet.py:3'> | <class 'mdtest_snippet.<locals of function '_'>.C1 @ src/mdtest_snippet.py:8'>`"
     C1.y = "problematic"
 
     class C2:

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

@@ -615,6 +615,22 @@ def _(x: type[typing.Any], y: typing.Any):
     reveal_type(super(x, y))  # revealed: <super: Any, Any>
 ```
 
+### Diagnostic when the invalid type is rendered very verbosely
+
+<!-- snapshot-diagnostics -->
+
+```py
+def coinflip() -> bool:
+    return False
+
+def f():
+    if coinflip():
+        class A: ...
+    else:
+        class A: ...
+    super(A, A())  # error: [invalid-super-argument]
+```
+
 ### Instance Member Access via `super`
 
 Accessing instance members through `super()` is not allowed.

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

@@ -643,6 +643,91 @@ reveal_type(Person.__init__)  # revealed: (self: Person, name: str) -> None
 Person(name="Alice")
 ```
 
+### Field specifiers using `**kwargs`
+
+Some field specifiers may use `**kwargs` to pass through standard parameters like `default`,
+`default_factory`, `init`, `kw_only`, and `alias`. This section tests that all these parameters work
+correctly when passed via `**kwargs` for all three kinds of transformers.
+
+#### Function-based transformer
+
+```py
+from typing import Any
+from typing_extensions import dataclass_transform
+
+def field(**kwargs: Any) -> Any: ...
+@dataclass_transform(field_specifiers=(field,))
+def create_model[T](cls: type[T]) -> type[T]:
+    return cls
+
+@create_model
+class Person:
+    id: int = field(init=False)
+    name: str
+    age: int = field(default=0)
+    tags: list[str] = field(default_factory=list)
+    email: str = field(kw_only=True)
+    internal_notes: str = field(alias="notes")
+
+# revealed: (self: Person, name: str, age: int = ..., tags: list[str] = ..., notes: str, *, email: str) -> None
+reveal_type(Person.__init__)
+
+Person("Alice", 30, [], "some notes", email="alice@example.com")
+Person("Bob", email="bob@example.com", notes="other notes")
+```
+
+#### Metaclass-based transformer
+
+```py
+from typing import Any
+from typing_extensions import dataclass_transform
+
+def field(**kwargs: Any) -> Any: ...
+@dataclass_transform(field_specifiers=(field,))
+class ModelMeta(type): ...
+
+class ModelBase(metaclass=ModelMeta): ...
+
+class Person(ModelBase):
+    id: int = field(init=False)
+    name: str
+    age: int = field(default=0)
+    tags: list[str] = field(default_factory=list)
+    email: str = field(kw_only=True)
+    internal_notes: str = field(alias="notes")
+
+# revealed: (self: Person, name: str, age: int = ..., tags: list[str] = ..., notes: str, *, email: str) -> None
+reveal_type(Person.__init__)
+
+Person("Alice", 30, [], "some notes", email="alice@example.com")
+Person("Bob", email="bob@example.com", notes="other notes")
+```
+
+#### Base-class-based transformer
+
+```py
+from typing import Any
+from typing_extensions import dataclass_transform
+
+def field(**kwargs: Any) -> Any: ...
+@dataclass_transform(field_specifiers=(field,))
+class ModelBase: ...
+
+class Person(ModelBase):
+    id: int = field(init=False)
+    name: str
+    age: int = field(default=0)
+    tags: list[str] = field(default_factory=list)
+    email: str = field(kw_only=True)
+    internal_notes: str = field(alias="notes")
+
+# revealed: (self: Person, name: str, age: int = ..., tags: list[str] = ..., notes: str, *, email: str) -> None
+reveal_type(Person.__init__)
+
+Person("Alice", 30, [], "some notes", email="alice@example.com")
+Person("Bob", email="bob@example.com", notes="other notes")
+```
+
 ### Support for `alias`
 
 The `alias` parameter in field specifiers allows providing an alternative name for the parameter in
@@ -868,4 +953,83 @@ reveal_type(t.key)  # revealed: int
 reveal_type(t.name)  # revealed: str
 ```
 
+## `__dataclass_fields__` and `DataclassInstance` protocol
+
+Classes created via `dataclass_transform` should have `__dataclass_fields__` and
+`__dataclass_params__` attributes, allowing them to satisfy the `DataclassInstance` protocol. This
+enables use of `dataclasses.fields`, `dataclasses.asdict`, `dataclasses.replace`, etc.
+
+### Function-based transformer
+
+```py
+from dataclasses import fields, asdict, replace, Field
+from typing import dataclass_transform, Any
+
+@dataclass_transform()
+def create_model[T](cls: type[T]) -> type[T]:
+    return cls
+
+@create_model
+class Person:
+    name: str
+    age: int
+
+p = Person("Alice", 30)
+
+reveal_type(Person.__dataclass_fields__)  # revealed: dict[str, Field[Any]]
+reveal_type(p.__dataclass_fields__)  # revealed: dict[str, Field[Any]]
+
+reveal_type(fields(Person))  # revealed: tuple[Field[Any], ...]
+reveal_type(asdict(p))  # revealed: dict[str, Any]
+reveal_type(replace(p, name="Bob"))  # revealed: Person
+```
+
+### Metaclass-based transformer
+
+```py
+from dataclasses import fields, asdict, replace, Field
+from typing import dataclass_transform, Any
+
+@dataclass_transform()
+class ModelMeta(type): ...
+
+class ModelBase(metaclass=ModelMeta): ...
+
+class Person(ModelBase):
+    name: str
+    age: int
+
+p = Person("Alice", 30)
+
+reveal_type(Person.__dataclass_fields__)  # revealed: dict[str, Field[Any]]
+reveal_type(p.__dataclass_fields__)  # revealed: dict[str, Field[Any]]
+
+reveal_type(fields(Person))  # revealed: tuple[Field[Any], ...]
+reveal_type(asdict(p))  # revealed: dict[str, Any]
+reveal_type(replace(p, name="Bob"))  # revealed: Person
+```
+
+### Base-class-based transformer
+
+```py
+from dataclasses import fields, asdict, replace, Field
+from typing import dataclass_transform, Any
+
+@dataclass_transform()
+class ModelBase: ...
+
+class Person(ModelBase):
+    name: str
+    age: int
+
+p = Person("Alice", 30)
+
+reveal_type(Person.__dataclass_fields__)  # revealed: dict[str, Field[Any]]
+reveal_type(p.__dataclass_fields__)  # revealed: dict[str, Field[Any]]
+
+reveal_type(fields(Person))  # revealed: tuple[Field[Any], ...]
+reveal_type(asdict(p))  # revealed: dict[str, Any]
+reveal_type(replace(p, name="Bob"))  # revealed: Person
+```
+
 [`typing.dataclass_transform`]: https://docs.python.org/3/library/typing.html#typing.dataclass_transform

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

@@ -195,3 +195,52 @@ class C:
 c = C()
 c.square("hello")  # error: [invalid-argument-type]
 ```
+
+## Types with the same name but from different files
+
+`module.py`:
+
+```py
+class Foo: ...
+
+def needs_a_foo(x: Foo): ...
+```
+
+`main.py`:
+
+```py
+from module import needs_a_foo
+
+class Foo: ...
+
+needs_a_foo(Foo())  # error: [invalid-argument-type]
+```
+
+## TypeVars with bounds that have the same name but are from different files
+
+In this case, using fully qualified names is *not* necessary.
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+`module.py`:
+
+```py
+class Foo: ...
+
+def needs_a_foo(x: Foo): ...
+```
+
+`main.py`:
+
+```py
+from module import needs_a_foo
+
+class Foo: ...
+
+def f[T: Foo](x: T) -> T:
+    needs_a_foo(x)  # error: [invalid-argument-type]
+    return x
+```

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

@@ -738,6 +738,8 @@ def f[T](x: T, y: Not[T]) -> T:
 
 ## `Callable` parameters
 
+### Class constructors
+
 We can recurse into the parameters and return values of `Callable` parameters to infer
 specializations of a generic function.
 
@@ -891,3 +893,46 @@ def _(x: list[str]):
     # error: [invalid-argument-type]
     reveal_type(accepts_callable(GenericClass)(x, x))
 ```
+
+### Don't include identical lower/upper bounds in type mapping multiple times
+
+This is was a performance regression reported in
+[ty#1968](https://github.com/astral-sh/ty/issues/1968). Before fixing this, we would see the
+`U ≤ M1 | ... | M7` upper bound 7 times. Since we intersect upper bounds before recording a single
+type mapping, we would perform 7 intersections. Each intersection would require 7^2 comparisons of
+the `Mx` types. We now have a simple heuristics that avoids processing any identical lower or upper
+bound more than once, since we know the extra copies cannot affect the result.
+
+```py
+from typing import Callable, Generic, TypeVar, Union
+
+class M1: ...
+class M2: ...
+class M3: ...
+class M4: ...
+class M5: ...
+class M6: ...
+class M7: ...
+
+Msg = Union[M1, M2, M3, M4, M5, M6, M7]
+
+T = TypeVar("T")
+U_co = TypeVar("U_co", covariant=True)
+
+class Stream(Generic[T]):
+    def apply(self, func: Callable[["Stream[T]"], "Stream[U_co]"]) -> "Stream[U_co]":
+        return func(self)
+
+TMsg = TypeVar("TMsg", bound=Msg)
+
+class Builder(Generic[TMsg]):
+    def build(self) -> Stream[TMsg]:
+        stream: Stream[TMsg] = Stream()
+        # TODO: no error
+        # error: [invalid-assignment]
+        stream = stream.apply(self._handler)
+        return stream
+
+    def _handler(self, stream: Stream[Msg]) -> Stream[Msg]:
+        return stream
+```

crates/ty_python_semantic/resources/mdtest/mro.md

@@ -289,6 +289,14 @@ reveal_type(x)  # revealed: <class 'A'> | <class 'B'>
 class Foo(x): ...
 
 reveal_mro(Foo)  # revealed: (<class 'Foo'>, Unknown, <class 'object'>)
+
+def f():
+    if returns_bool():
+        class C: ...
+    else:
+        class C: ...
+
+    class D(C): ...  # error: [unsupported-base]
 ```
 
 ## `UnionType` instances are now allowed as a base
@@ -393,7 +401,7 @@ else:
 # revealed: (<class 'B'>, <class 'X'>, <class 'Y'>, <class 'O'>, <class 'object'>) | (<class 'B'>, <class 'Y'>, <class 'X'>, <class 'O'>, <class 'object'>)
 reveal_mro(B)
 
-# error: 12 [unsupported-base] "Unsupported class base with type `<class 'B'> | <class 'B'>`"
+# error: 12 [unsupported-base] "Unsupported class base with type `<class 'mdtest_snippet.B @ src/mdtest_snippet.py:25'> | <class 'mdtest_snippet.B @ src/mdtest_snippet.py:28'>`"
 class Z(A, B): ...
 
 reveal_mro(Z)  # revealed: (<class 'Z'>, Unknown, <class 'object'>)

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

@@ -104,6 +104,8 @@ class C:
     value: str | None
 
 def foo(c: C):
+    # The truthiness check `c.value` narrows to `str & ~AlwaysFalsy`.
+    # The subsequent `len(c.value)` doesn't narrow further since `str` is not narrowable by len().
     if c.value and len(c.value):
         reveal_type(c.value)  # revealed: str & ~AlwaysFalsy
 
@@ -114,7 +116,7 @@ def foo(c: C):
     if c.value is None or not len(c.value):
         reveal_type(c.value)  # revealed: str | None
     else:  # c.value is not None and len(c.value)
-        # TODO: should be # `str & ~AlwaysFalsy`
+        # `c.value is not None` narrows to `str`, but `str` is not narrowable by len().
         reveal_type(c.value)  # revealed: str
 ```
 

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

@@ -0,0 +1,131 @@
+# Narrowing for `len(..)` checks
+
+When `len(x)` is used in a boolean context, we can narrow the type of `x` based on whether `len(x)`
+is truthy (non-zero) or falsy (zero).
+
+We apply `~AlwaysFalsy` narrowing when ANY part of the type is narrowable (string/bytes literals,
+`LiteralString`, tuples). This removes types that are always falsy (like `Literal[""]`) while
+leaving non-narrowable types (like `str`, `list`) unchanged.
+
+## String literals
+
+The intersection with `~AlwaysFalsy` simplifies to just the non-empty literal.
+
+```py
+from typing import Literal
+
+def _(x: Literal["foo", ""]):
+    if len(x):
+        reveal_type(x)  # revealed: Literal["foo"]
+    else:
+        reveal_type(x)  # revealed: Literal[""]
+```
+
+## Bytes literals
+
+```py
+from typing import Literal
+
+def _(x: Literal[b"foo", b""]):
+    if len(x):
+        reveal_type(x)  # revealed: Literal[b"foo"]
+    else:
+        reveal_type(x)  # revealed: Literal[b""]
+```
+
+## LiteralString
+
+```toml
+[environment]
+python-version = "3.11"
+```
+
+```py
+from typing import LiteralString
+
+def _(x: LiteralString):
+    if len(x):
+        reveal_type(x)  # revealed: LiteralString & ~Literal[""]
+    else:
+        reveal_type(x)  # revealed: Literal[""]
+```
+
+## Tuples
+
+Ideally we'd narrow these types further, e.g. to `tuple[int, ...] & ~tuple[()]` in the positive case
+and `tuple[()]` in the negative case (see <https://github.com/astral-sh/ty/issues/560>).
+
+```py
+def _(x: tuple[int, ...]):
+    if len(x):
+        reveal_type(x)  # revealed: tuple[int, ...] & ~AlwaysFalsy
+    else:
+        reveal_type(x)  # revealed: tuple[int, ...] & ~AlwaysTruthy
+```
+
+## Unions of narrowable types
+
+```py
+from typing import Literal
+
+def _(x: Literal["foo", ""] | tuple[int, ...]):
+    if len(x):
+        reveal_type(x)  # revealed: Literal["foo"] | (tuple[int, ...] & ~AlwaysFalsy)
+    else:
+        reveal_type(x)  # revealed: Literal[""] | (tuple[int, ...] & ~AlwaysTruthy)
+```
+
+## Types that are not narrowed
+
+For `str`, `list`, and other types where a subclass could have a `__bool__` that disagrees with
+`__len__`, we do not narrow:
+
+```py
+def not_narrowed_str(x: str):
+    if len(x):
+        # No narrowing because `str` could be subclassed with a custom `__bool__`
+        reveal_type(x)  # revealed: str
+
+def not_narrowed_list(x: list[int]):
+    if len(x):
+        # No narrowing because `list` could be subclassed with a custom `__bool__`
+        reveal_type(x)  # revealed: list[int]
+```
+
+## Mixed unions (narrowable and non-narrowable)
+
+When a union contains both narrowable and non-narrowable types, we narrow the narrowable parts while
+leaving the non-narrowable parts unchanged:
+
+```py
+from typing import Literal
+
+def _(x: Literal["foo", ""] | list[int]):
+    if len(x):
+        # `Literal[""]` is removed, `list[int]` is unchanged
+        reveal_type(x)  # revealed: Literal["foo"] | list[int]
+    else:
+        reveal_type(x)  # revealed: Literal[""] | list[int]
+```
+
+## Narrowing away empty literals
+
+This pattern is common when a prior truthiness check narrows a type, and then a conditional
+expression adds an empty literal back:
+
+```py
+def _(lines: list[str]):
+    for line in lines:
+        if not line:
+            continue
+
+        reveal_type(line)  # revealed: str & ~AlwaysFalsy
+        value = line if len(line) < 3 else ""
+        reveal_type(value)  # revealed: (str & ~AlwaysFalsy) | Literal[""]
+
+        if len(value):
+            # `Literal[""]` is removed, `str & ~AlwaysFalsy` is unchanged
+            reveal_type(value)  # revealed: str & ~AlwaysFalsy
+            # Accessing value[0] is safe here
+            _ = value[0]
+```

crates/ty_python_semantic/resources/mdtest/snapshots/attribute_assignment…_-_Attribute_assignment_-_Setting_attributes_o…_(467e26496f4c0c13).snap

@@ -37,7 +37,7 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/attribute_as
 # Diagnostics
 
 ```
-error[invalid-assignment]: Object of type `Literal[1]` is not assignable to attribute `attr` on type `<class 'C1'> | <class 'C1'>`
+error[invalid-assignment]: Object of type `Literal[1]` is not assignable to attribute `attr` on type `<class 'mdtest_snippet.<locals of function '_'>.C1 @ src/mdtest_snippet.py:3'> | <class 'mdtest_snippet.<locals of function '_'>.C1 @ src/mdtest_snippet.py:7'>`
   --> src/mdtest_snippet.py:11:5
    |
 10 |     # TODO: The error message here could be improved to explain why the assignment fails.

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_argument_typ…_-_Invalid_argument_typ…_-_TypeVars_with_bounds…_(25b61918ea9f5644).snap

@@ -0,0 +1,53 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_argument_type.md - Invalid argument type diagnostics - TypeVars with bounds that have the same name but are from different files
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_argument_type.md
+---
+
+# Python source files
+
+## module.py
+
+```
+1 | class Foo: ...
+2 | 
+3 | def needs_a_foo(x: Foo): ...
+```
+
+## main.py
+
+```
+1 | from module import needs_a_foo
+2 | 
+3 | class Foo: ...
+4 | 
+5 | def f[T: Foo](x: T) -> T:
+6 |     needs_a_foo(x)  # error: [invalid-argument-type]
+7 |     return x
+```
+
+# Diagnostics
+
+```
+error[invalid-argument-type]: Argument to function `needs_a_foo` is incorrect
+ --> src/main.py:6:17
+  |
+5 | def f[T: Foo](x: T) -> T:
+6 |     needs_a_foo(x)  # error: [invalid-argument-type]
+  |                 ^ Expected `Foo`, found `T@f`
+7 |     return x
+  |
+info: Function defined here
+ --> src/module.py:3:5
+  |
+1 | class Foo: ...
+2 |
+3 | def needs_a_foo(x: Foo): ...
+  |     ^^^^^^^^^^^ ------ Parameter declared here
+  |
+info: rule `invalid-argument-type` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/invalid_argument_typ…_-_Invalid_argument_typ…_-_Types_with_the_same_…_(34531e82322f6f21).snap

@@ -0,0 +1,51 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: invalid_argument_type.md - Invalid argument type diagnostics - Types with the same name but from different files
+mdtest path: crates/ty_python_semantic/resources/mdtest/diagnostics/invalid_argument_type.md
+---
+
+# Python source files
+
+## module.py
+
+```
+1 | class Foo: ...
+2 | 
+3 | def needs_a_foo(x: Foo): ...
+```
+
+## main.py
+
+```
+1 | from module import needs_a_foo
+2 | 
+3 | class Foo: ...
+4 | 
+5 | needs_a_foo(Foo())  # error: [invalid-argument-type]
+```
+
+# Diagnostics
+
+```
+error[invalid-argument-type]: Argument to function `needs_a_foo` is incorrect
+ --> src/main.py:5:13
+  |
+3 | class Foo: ...
+4 |
+5 | needs_a_foo(Foo())  # error: [invalid-argument-type]
+  |             ^^^^^ Expected `module.Foo`, found `main.Foo`
+  |
+info: Function defined here
+ --> src/module.py:3:5
+  |
+1 | class Foo: ...
+2 |
+3 | def needs_a_foo(x: Foo): ...
+  |     ^^^^^^^^^^^ ------ Parameter declared here
+  |
+info: rule `invalid-argument-type` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/mro.md_-_Method_Resolution_Or…_-_`__bases__`_includes…_(d2532518c44112c8).snap

@@ -31,17 +31,25 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/mro.md
 17 | class Foo(x): ...
 18 | 
 19 | reveal_mro(Foo)  # revealed: (<class 'Foo'>, Unknown, <class 'object'>)
+20 | 
+21 | def f():
+22 |     if returns_bool():
+23 |         class C: ...
+24 |     else:
+25 |         class C: ...
+26 | 
+27 |     class D(C): ...  # error: [unsupported-base]
 ```
 
 # Diagnostics
 
 ```
-warning[unsupported-base]: Unsupported class base with type `<class 'A'> | <class 'B'>`
+warning[unsupported-base]: Unsupported class base
   --> src/mdtest_snippet.py:17:11
    |
 16 | # error: 11 [unsupported-base] "Unsupported class base with type `<class 'A'> | <class 'B'>`"
 17 | class Foo(x): ...
-   |           ^
+   |           ^ Has type `<class 'A'> | <class 'B'>`
 18 |
 19 | reveal_mro(Foo)  # revealed: (<class 'Foo'>, Unknown, <class 'object'>)
    |
@@ -50,3 +58,18 @@ info: Only class objects or `Any` are supported as class bases
 info: rule `unsupported-base` is enabled by default
 
 ```
+
+```
+warning[unsupported-base]: Unsupported class base
+  --> src/mdtest_snippet.py:27:13
+   |
+25 |         class C: ...
+26 |
+27 |     class D(C): ...  # error: [unsupported-base]
+   |             ^ Has type `<class 'mdtest_snippet.<locals of function 'f'>.C @ src/mdtest_snippet.py:23'> | <class 'mdtest_snippet.<locals of function 'f'>.C @ src/mdtest_snippet.py:25'>`
+   |
+info: ty cannot resolve a consistent MRO for class `D` due to this base
+info: Only class objects or `Any` are supported as class bases
+info: rule `unsupported-base` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/mro.md_-_Method_Resolution_Or…_-_`__bases__`_lists_th…_(6f8d0bf648c4b305).snap

@@ -47,13 +47,13 @@ info: rule `invalid-base` is enabled by default
 ```
 
 ```
-warning[unsupported-base]: Unsupported class base with type `Foo`
+warning[unsupported-base]: Unsupported class base
  --> src/mdtest_snippet.py:6:11
   |
 4 |         return ()
 5 |
 6 | class Bar(Foo()): ...  # error: [unsupported-base]
-  |           ^^^^^
+  |           ^^^^^ Has type `Foo`
 7 | class Bad1:
 8 |     def __mro_entries__(self, bases, extra_arg):
   |

crates/ty_python_semantic/resources/mdtest/snapshots/super.md_-_Super_-_Invalid_Usages_-_Diagnostic_when_the_…_(93e8ab913ead83b2).snap

@@ -0,0 +1,39 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: super.md - Super - Invalid Usages - Diagnostic when the invalid type is rendered very verbosely
+mdtest path: crates/ty_python_semantic/resources/mdtest/class/super.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | def coinflip() -> bool:
+2 |     return False
+3 | 
+4 | def f():
+5 |     if coinflip():
+6 |         class A: ...
+7 |     else:
+8 |         class A: ...
+9 |     super(A, A())  # error: [invalid-super-argument]
+```
+
+# Diagnostics
+
+```
+error[invalid-super-argument]: Argument is not a valid class
+ --> src/mdtest_snippet.py:9:5
+  |
+7 |     else:
+8 |         class A: ...
+9 |     super(A, A())  # error: [invalid-super-argument]
+  |     ^^^^^^^^^^^^^ Argument has type `<class 'mdtest_snippet.<locals of function 'f'>.A @ src/mdtest_snippet.py:6'> | <class 'mdtest_snippet.<locals of function 'f'>.A @ src/mdtest_snippet.py:8'>`
+  |
+info: rule `invalid-super-argument` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/typed_dict.md

@@ -1726,5 +1726,298 @@ reveal_type(actual_td)  # revealed: ActualTypedDict
 reveal_type(actual_td["name"])  # revealed: str
 ```
 
+## Disjointness with other `TypedDict`s
+
+Two `TypedDict` types are disjoint if it's impossible to come up with a third (fully-static)
+`TypedDict` that's assignable to both. The simplest way to establish this is if both sides have
+fields with the same name but disjoint types:
+
+```py
+from typing import TypedDict, final
+from typing_extensions import ReadOnly
+from ty_extensions import static_assert, is_disjoint_from
+
+# Two simple disjoint types, to avoid relying on `@disjoint_base` special cases for built-ins like
+# `int` and `str`.
+@final
+class Final1: ...
+
+@final
+class Final2: ...
+
+static_assert(is_disjoint_from(Final1, Final2))
+
+class DisjointTD1(TypedDict):
+    # Make this example `ReadOnly` because that actually ends up checking the field types for
+    # disjointness in practice. Mutable fields are stricter. We'll get to that below.
+    disjoint: ReadOnly[Final1]
+    # While we're here: It doesn't matter how many other compatible fields there are. Just the one
+    # incompatible field above establishes disjointness.
+    common1: object
+    common2: object
+
+class DisjointTD2(TypedDict):
+    disjoint: ReadOnly[Final2]
+    common1: object
+    common2: object
+
+static_assert(is_disjoint_from(DisjointTD1, DisjointTD2))
+```
+
+However, note that most pairs of non-final classes are *not* disjoint from each other, even if
+neither inherits from the other, because we could define a third class that multiply-inherits from
+both. `TypedDict` disjointness takes this into account. For example:
+
+```py
+from ty_extensions import is_assignable_to
+
+class NonFinal1: ...
+class NonFinal2: ...
+class CommonSub(NonFinal1, NonFinal2): ...
+
+static_assert(not is_disjoint_from(NonFinal1, NonFinal2))
+static_assert(not is_assignable_to(NonFinal1, NonFinal2))
+static_assert(is_assignable_to(CommonSub, NonFinal1))
+static_assert(is_assignable_to(CommonSub, NonFinal2))
+
+class NonDisjointTD1(TypedDict):
+    non_disjoint: ReadOnly[NonFinal1]
+    # While we're here: It doesn't matter how many "extra" fields there are, or what order the
+    # fields are in. Only shared field names can establish disjointness.
+    extra1: int
+
+class NonDisjointTD2(TypedDict):
+    extra2: str
+    non_disjoint: ReadOnly[NonFinal2]
+
+class CommonSubTD(TypedDict):
+    extra2: str
+    extra1: int
+    non_disjoint: ReadOnly[CommonSub]
+
+# The first two TDs above are not assignable in either direction...
+static_assert(not is_assignable_to(NonDisjointTD1, NonDisjointTD2))
+static_assert(not is_assignable_to(NonDisjointTD2, NonDisjointTD1))
+# ...but they're still not disjoint...
+static_assert(not is_disjoint_from(NonDisjointTD1, NonDisjointTD2))
+# ...because the third TD above is assignable to both of them.
+static_assert(is_assignable_to(CommonSubTD, NonDisjointTD1))
+static_assert(is_assignable_to(CommonSubTD, NonDisjointTD2))
+static_assert(not is_disjoint_from(CommonSubTD, NonDisjointTD1))
+static_assert(not is_disjoint_from(CommonSubTD, NonDisjointTD2))
+```
+
+We made the important fields `ReadOnly` above, because those only establish disjointness when
+they're disjoint themselves. However, the rules for mutable fields are stricter. Mutable fields in
+common need to have *compatible* types (in the fully-static case, equivalent types):
+
+```py
+from typing import Any, Generic, TypeVar
+
+class IntTD(TypedDict):
+    x: int
+
+class BoolTD(TypedDict):
+    x: bool
+
+# `bool` is assignable to `int`, but `int` is not assignable to `bool`. If `x` was `ReadOnly` (even,
+# as we'll see below, only on the `int` side), then these two TDs would not be disjoint, but in this
+# mutable case they are.
+
+static_assert(is_disjoint_from(IntTD, BoolTD))
+static_assert(is_disjoint_from(BoolTD, IntTD))
+
+# Gradual types: `int` is compatible with `bool | Any`, because that could materialize to
+# `bool | int`, which is just `int`. (And `int | Any` and `bool | Any` are compatible with each
+# other for the same reason.) However, `bool` is *not* compatible with `int | Any`, because there's
+# no materialization that's equivalent to `bool`.
+
+class IntOrAnyTD(TypedDict):
+    x: int | Any
+
+class BoolOrAnyTD(TypedDict):
+    x: bool | Any
+
+static_assert(not is_disjoint_from(IntTD, IntOrAnyTD))
+static_assert(not is_disjoint_from(IntOrAnyTD, IntTD))
+static_assert(not is_disjoint_from(IntTD, BoolOrAnyTD))
+static_assert(not is_disjoint_from(BoolOrAnyTD, IntTD))
+
+static_assert(not is_disjoint_from(IntOrAnyTD, BoolOrAnyTD))
+static_assert(not is_disjoint_from(BoolOrAnyTD, IntOrAnyTD))
+
+static_assert(is_disjoint_from(BoolTD, IntOrAnyTD))
+static_assert(is_disjoint_from(IntOrAnyTD, BoolTD))
+static_assert(not is_disjoint_from(BoolTD, BoolOrAnyTD))
+static_assert(not is_disjoint_from(BoolOrAnyTD, BoolTD))
+
+# `Any` is compatible with everything.
+
+class AnyTD(TypedDict):
+    x: Any
+
+static_assert(not is_disjoint_from(IntTD, AnyTD))
+static_assert(not is_disjoint_from(AnyTD, IntTD))
+static_assert(not is_disjoint_from(BoolTD, AnyTD))
+static_assert(not is_disjoint_from(AnyTD, BoolTD))
+static_assert(not is_disjoint_from(IntOrAnyTD, AnyTD))
+static_assert(not is_disjoint_from(AnyTD, IntOrAnyTD))
+static_assert(not is_disjoint_from(BoolOrAnyTD, AnyTD))
+static_assert(not is_disjoint_from(AnyTD, BoolOrAnyTD))
+static_assert(not is_disjoint_from(AnyTD, AnyTD))
+
+# This works with generic `TypedDict`s too.
+
+class TwoIntsTD(TypedDict):
+    x: int
+    y: int
+
+class TwoBoolsTD(TypedDict):
+    x: bool
+    y: bool
+
+class IntBoolTD(TypedDict):
+    x: int
+    y: bool
+
+T = TypeVar("T")
+
+class TwoGenericTD(TypedDict, Generic[T]):
+    x: T
+    y: T
+
+static_assert(not is_disjoint_from(TwoGenericTD[Any], TwoIntsTD))
+static_assert(not is_disjoint_from(TwoGenericTD[int], TwoIntsTD))
+static_assert(is_disjoint_from(TwoGenericTD[bool], TwoIntsTD))
+static_assert(not is_disjoint_from(TwoGenericTD[Any], TwoBoolsTD))
+static_assert(is_disjoint_from(TwoGenericTD[int], TwoBoolsTD))
+static_assert(not is_disjoint_from(TwoGenericTD[bool], TwoBoolsTD))
+# TODO: T can't be compatible with both `int` and `bool` at the same time, so these types should be
+# disjoint, regardless of the materialization of `T`.
+static_assert(not is_disjoint_from(TwoGenericTD[Any], IntBoolTD))
+```
+
+If one side is mutable but the other is not, then a "third `TypedDict` that's assignable to both"
+would have to have the same type as the mutable side, so we establish disjointness if that type
+isn't assignable to the immutable side:
+
+```py
+class ReadOnlyIntTD(TypedDict):
+    x: ReadOnly[int]
+
+class ReadOnlyBoolTD(TypedDict):
+    x: ReadOnly[bool]
+
+static_assert(not is_disjoint_from(ReadOnlyIntTD, ReadOnlyBoolTD))
+static_assert(not is_disjoint_from(ReadOnlyBoolTD, ReadOnlyIntTD))
+static_assert(not is_disjoint_from(BoolTD, ReadOnlyIntTD))
+static_assert(not is_disjoint_from(ReadOnlyIntTD, BoolTD))
+static_assert(is_disjoint_from(IntTD, ReadOnlyBoolTD))
+static_assert(is_disjoint_from(ReadOnlyBoolTD, IntTD))
+```
+
+With mutability above we were able to make the simplifying assumption that the "third `TypedDict`
+that's assignable to both" has only mutable fields, because a mutable field is always assignable to
+its immutable counterpart. However, `Required` vs `NotRequired` are more complicated, because a a
+`Required` field is *not* necessarily assignable to its `NotRequired` counterpart. In particular, if
+a `NotRequired` field is also mutable (intuitively, if we're allowed to `del` it), then no
+`Required` field is ever assignable to it. So, if either side is `NotRequired` and mutable, and the
+other side is `Required` (regardless of mutability), then that's sufficient to establish
+disjointness:
+
+```py
+from typing_extensions import NotRequired
+
+class NotRequiredIntTD(TypedDict):
+    x: NotRequired[int]
+
+class NotRequiredReadOnlyIntTD(TypedDict):
+    x: NotRequired[ReadOnly[int]]
+
+static_assert(is_disjoint_from(NotRequiredIntTD, IntTD))
+static_assert(is_disjoint_from(IntTD, NotRequiredIntTD))
+static_assert(is_disjoint_from(NotRequiredIntTD, ReadOnlyIntTD))
+static_assert(is_disjoint_from(ReadOnlyIntTD, NotRequiredIntTD))
+static_assert(not is_disjoint_from(NotRequiredIntTD, NotRequiredReadOnlyIntTD))
+static_assert(not is_disjoint_from(NotRequiredReadOnlyIntTD, NotRequiredIntTD))
+```
+
+All those rules put together give us the "full disjointness table". We've pretty well tested above
+that disjointness is symmetrical, so here we won't worry about asserting both directions for each
+check:
+
+```py
+class NotRequiredBoolTD(TypedDict):
+    x: NotRequired[bool]
+
+class NotRequiredReadOnlyBoolTD(TypedDict):
+    x: NotRequired[ReadOnly[bool]]
+
+static_assert(not is_disjoint_from(IntTD, IntTD))
+static_assert(is_disjoint_from(IntTD, BoolTD))
+static_assert(not is_disjoint_from(IntTD, ReadOnlyIntTD))
+static_assert(is_disjoint_from(IntTD, ReadOnlyBoolTD))
+static_assert(is_disjoint_from(IntTD, NotRequiredIntTD))
+static_assert(is_disjoint_from(IntTD, NotRequiredBoolTD))
+static_assert(not is_disjoint_from(IntTD, NotRequiredReadOnlyIntTD))
+static_assert(is_disjoint_from(IntTD, NotRequiredReadOnlyBoolTD))
+static_assert(not is_disjoint_from(ReadOnlyIntTD, BoolTD))
+static_assert(not is_disjoint_from(ReadOnlyIntTD, ReadOnlyIntTD))
+static_assert(not is_disjoint_from(ReadOnlyIntTD, ReadOnlyBoolTD))
+static_assert(is_disjoint_from(ReadOnlyIntTD, NotRequiredIntTD))
+static_assert(is_disjoint_from(ReadOnlyIntTD, NotRequiredBoolTD))
+static_assert(not is_disjoint_from(ReadOnlyIntTD, NotRequiredReadOnlyIntTD))
+static_assert(not is_disjoint_from(ReadOnlyIntTD, NotRequiredReadOnlyBoolTD))
+static_assert(is_disjoint_from(NotRequiredIntTD, BoolTD))
+static_assert(is_disjoint_from(NotRequiredIntTD, ReadOnlyBoolTD))
+static_assert(not is_disjoint_from(NotRequiredIntTD, NotRequiredIntTD))
+static_assert(is_disjoint_from(NotRequiredIntTD, NotRequiredBoolTD))
+static_assert(not is_disjoint_from(NotRequiredIntTD, NotRequiredReadOnlyIntTD))
+static_assert(is_disjoint_from(NotRequiredIntTD, NotRequiredReadOnlyBoolTD))
+static_assert(not is_disjoint_from(NotRequiredReadOnlyIntTD, BoolTD))
+static_assert(not is_disjoint_from(NotRequiredReadOnlyIntTD, ReadOnlyBoolTD))
+static_assert(not is_disjoint_from(NotRequiredReadOnlyIntTD, NotRequiredBoolTD))
+static_assert(not is_disjoint_from(NotRequiredReadOnlyIntTD, NotRequiredReadOnlyIntTD))
+static_assert(not is_disjoint_from(NotRequiredReadOnlyIntTD, NotRequiredReadOnlyBoolTD))
+static_assert(not is_disjoint_from(BoolTD, BoolTD))
+static_assert(not is_disjoint_from(BoolTD, ReadOnlyBoolTD))
+static_assert(is_disjoint_from(BoolTD, NotRequiredBoolTD))
+static_assert(not is_disjoint_from(BoolTD, NotRequiredReadOnlyBoolTD))
+static_assert(not is_disjoint_from(ReadOnlyBoolTD, ReadOnlyBoolTD))
+static_assert(is_disjoint_from(ReadOnlyBoolTD, NotRequiredBoolTD))
+static_assert(not is_disjoint_from(ReadOnlyBoolTD, NotRequiredReadOnlyBoolTD))
+static_assert(not is_disjoint_from(NotRequiredBoolTD, NotRequiredBoolTD))
+static_assert(not is_disjoint_from(NotRequiredBoolTD, NotRequiredReadOnlyBoolTD))
+static_assert(not is_disjoint_from(NotRequiredReadOnlyBoolTD, NotRequiredReadOnlyBoolTD))
+```
+
+## Disjointness with other types
+
+```py
+from typing import TypedDict, Mapping
+from ty_extensions import static_assert, is_disjoint_from
+
+class TD(TypedDict):
+    x: int
+
+class RegularNonTD: ...
+
+static_assert(not is_disjoint_from(TD, object))
+static_assert(not is_disjoint_from(TD, Mapping[str, object]))
+static_assert(is_disjoint_from(TD, Mapping[int, object]))
+static_assert(is_disjoint_from(TD, RegularNonTD))
+
+# TODO: We approximate disjointness with other types `T` by asking whether `dict[str, Any]` is
+# assignable to `T`. That covers common cases like the ones above, but does it have some false
+# negatives with `dict` types. A `TypedDict` is almost never assignable to a `dict` (or vice versa),
+# even when all of the `TypedDict`'s field types match the `dict`'s value type (and are mutable).
+# The problem is that the `TypedDict` could have been assigned to from *another* `TypedDict` with
+# additional fields, and we don't usually know anything about the types or mutability of those. On
+# the other hand, the assignment to `dict` can be allowed if the `TypedDict` has mutable
+# `extra_items` of a compatible type. See: https://typing.python.org/en/latest/spec/typeddict.html#subtyping-with-dict
+static_assert(is_disjoint_from(TD, dict[str, int]))  # error: [static-assert-error]
+static_assert(is_disjoint_from(TD, dict[str, str]))  # error: [static-assert-error]
+```
+
 [subtyping section]: https://typing.python.org/en/latest/spec/typeddict.html#subtyping-between-typeddict-types
 [`typeddict`]: https://typing.python.org/en/latest/spec/typeddict.html

crates/ty_python_semantic/src/lib.rs

@@ -17,7 +17,7 @@ pub use module_resolver::{
     resolve_real_module_confident, resolve_real_shadowable_module, system_module_search_paths,
 };
 pub use program::{
-    Program, ProgramSettings, PythonVersionFileSource, PythonVersionSource,
+    MisconfigurationMode, Program, ProgramSettings, PythonVersionFileSource, PythonVersionSource,
     PythonVersionWithSource, SearchPathSettings,
 };
 pub use python_platform::PythonPlatform;