support rendering __doc__ on hover

This is a common footgun, see the example in
https://github.com/astral-sh/ruff/issues/13014#issuecomment-3411496519

Fixes #13014 , fixes #13031

.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 \

_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_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_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/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,

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_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/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/ty_ide/src/hover.rs

@@ -1183,13 +1183,13 @@ 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 +1243,13 @@ 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 +1303,7 @@ def ab(a: int):
             .build();
 
         assert_snapshot!(test.hover(), @r"
-        (
+        def ab(
             a: int,
             b: int
         ) -> Unknown
@@ -1312,7 +1312,7 @@ def ab(a: int):
 
         ---------------------------------------------
         ```python
-        (
+        def ab(
             a: int,
             b: int
         ) -> Unknown
@@ -1369,13 +1369,13 @@ 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 +1433,7 @@ def ab(a: int, *, c: int):
             .build();
 
         assert_snapshot!(test.hover(), @r"
-        (
+        def ab(
             a: int,
             *,
             b: int
@@ -1443,7 +1443,7 @@ def ab(a: int, *, c: int):
 
         ---------------------------------------------
         ```python
-        (
+        def ab(
             a: int,
             *,
             b: int
@@ -1505,7 +1505,7 @@ def ab(a: int, *, c: int):
             .build();
 
         assert_snapshot!(test.hover(), @r"
-        (
+        def ab(
             a: int,
             *,
             c: int
@@ -1515,7 +1515,7 @@ def ab(a: int, *, c: int):
 
         ---------------------------------------------
         ```python
-        (
+        def ab(
             a: int,
             *,
             c: int
@@ -1564,11 +1564,11 @@ 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 +1577,11 @@ def ab(a: int, *, c: int):
 
         ---------------------------------------------
         ```python
-        (
+        def foo(
             a: int,
             b
         ) -> Unknown
-        (
+        def foo(
             a: str,
             b
         ) -> Unknown
@@ -1628,15 +1628,15 @@ 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
@@ -2739,6 +2739,86 @@ def function():
         assert_snapshot!(test.hover(), @"Hover provided no content");
     }
 
+    #[test]
+    fn hover_dunder_doc() {
+        let test = cursor_test(
+            r#"
+            class My<CURSOR>Class:
+                __doc__ = "hello there"
+            "#,
+        );
+
+        assert_snapshot!(test.hover(), @r#"
+        <class 'MyClass'>
+        ---------------------------------------------
+        hello there
+
+        ---------------------------------------------
+        ```xml
+        <class 'MyClass'>
+        ```
+        ---
+        hello there
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:2:7
+          |
+        2 | class MyClass:
+          |       ^^-^^^^
+          |       | |
+          |       | Cursor offset
+          |       source
+        3 |     __doc__ = "hello there"
+          |
+        "#);
+    }
+
+    #[test]
+    fn hover_dunder_doc_complex() {
+        let test = cursor_test(
+            r#"
+            class My<CURSOR>Class:
+                __doc__ = (
+                    r"""This is some extremely complex docstring
+
+                Designed to make
+                """
+                    + r"""
+
+                A typechecker
+            """
+                    """
+                Fall to its knees and sob
+            """
+                    r"""
+                Witness my works and 
+                weep before them
+                """
+                )
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @r#"
+        <class 'MyClass'>
+        ---------------------------------------------
+        ```xml
+        <class 'MyClass'>
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:2:7
+          |
+        2 | class MyClass:
+          |       ^^-^^^^
+          |       | |
+          |       | Cursor offset
+          |       source
+        3 |     __doc__ = (
+        4 |         r"""This is some extremely complex docstring
+          |
+        "#);
+    }
+
     #[test]
     fn hover_class_typevar_variance() {
         let test = cursor_test(
@@ -3233,12 +3313,12 @@ 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_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/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/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

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/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/src/semantic_index/definition.rs

@@ -2,7 +2,7 @@ use std::ops::Deref;
 
 use ruff_db::files::{File, FileRange};
 use ruff_db::parsed::{ParsedModuleRef, parsed_module};
-use ruff_python_ast as ast;
+use ruff_python_ast::{self as ast, Expr};
 use ruff_text_size::{Ranged, TextRange};
 
 use crate::Db;
@@ -133,6 +133,10 @@ pub(crate) fn module_docstring(db: &dyn Db, file: File) -> Option<String> {
 
 /// Extract a docstring from a function, module, or class body.
 fn docstring_from_body(body: &[ast::Stmt]) -> Option<&ast::ExprStringLiteral> {
+    docstring_from_body_normal(body).or_else(|| docstring_from_body_dunder_doc(body))
+}
+
+fn docstring_from_body_normal(body: &[ast::Stmt]) -> Option<&ast::ExprStringLiteral> {
     let stmt = body.first()?;
     // Require the docstring to be a standalone expression.
     let ast::Stmt::Expr(ast::StmtExpr {
@@ -147,6 +151,27 @@ fn docstring_from_body(body: &[ast::Stmt]) -> Option<&ast::ExprStringLiteral> {
     value.as_string_literal_expr()
 }
 
+fn docstring_from_body_dunder_doc(body: &[ast::Stmt]) -> Option<&ast::ExprStringLiteral> {
+    for stmt in body {
+        let Some(stmt) = stmt.as_assign_stmt() else {
+            continue;
+        };
+        let [Expr::Name(name)] = &stmt.targets[..] else {
+            continue;
+        };
+        if name.id.as_str() != "__doc__" {
+            continue;
+        }
+        let Expr::StringLiteral(literal) = &*stmt.value else {
+            continue;
+        };
+
+        return Some(literal);
+    }
+
+    None
+}
+
 /// One or more [`Definition`]s.
 #[derive(Debug, Default, PartialEq, Eq, salsa::Update, get_size2::GetSize)]
 pub struct Definitions<'db> {

crates/ty_python_semantic/src/types/bound_super.rs

@@ -76,15 +76,25 @@ impl<'db> BoundSuperError<'db> {
             BoundSuperError::InvalidPivotClassType { pivot_class } => {
                 if let Some(builder) = context.report_lint(&INVALID_SUPER_ARGUMENT, node) {
                     match pivot_class {
-                        Type::GenericAlias(alias) => builder.into_diagnostic(format_args!(
-                            "`types.GenericAlias` instance `{}` is not a valid class",
-                            alias.display_with(context.db(), DisplaySettings::default()),
-                        )),
-                        _ => builder.into_diagnostic(format_args!(
-                            "`{pivot_class}` is not a valid class",
-                            pivot_class = pivot_class.display(context.db()),
-                        )),
-                    };
+                        Type::GenericAlias(alias) => {
+                            builder.into_diagnostic(format_args!(
+                                "`types.GenericAlias` instance `{}` is not a valid class",
+                                alias.display_with(context.db(), DisplaySettings::default()),
+                            ));
+                        }
+                        _ => {
+                            let mut diagnostic =
+                                builder.into_diagnostic("Argument is not a valid class");
+                            diagnostic.set_primary_message(format_args!(
+                                "Argument has type `{}`",
+                                pivot_class.display(context.db())
+                            ));
+                            diagnostic.set_concise_message(format_args!(
+                                "`{}` is not a valid class",
+                                pivot_class.display(context.db()),
+                            ));
+                        }
+                    }
                 }
             }
             BoundSuperError::FailingConditionCheck {

crates/ty_python_semantic/src/types/diagnostic.rs

@@ -3478,13 +3478,16 @@ fn report_unsupported_base(
     let Some(builder) = context.report_lint(&UNSUPPORTED_BASE, base_node) else {
         return;
     };
-    let mut diagnostic = builder.into_diagnostic(format_args!(
+    let db = context.db();
+    let mut diagnostic = builder.into_diagnostic("Unsupported class base");
+    diagnostic.set_primary_message(format_args!("Has type `{}`", base_type.display(db)));
+    diagnostic.set_concise_message(format_args!(
         "Unsupported class base with type `{}`",
-        base_type.display(context.db())
+        base_type.display(db)
     ));
     diagnostic.info(format_args!(
         "ty cannot resolve a consistent MRO for class `{}` due to this base",
-        class.name(context.db())
+        class.name(db)
     ));
     diagnostic.info("Only class objects or `Any` are supported as class bases");
 }

crates/ty_python_semantic/src/types/display.rs

@@ -15,6 +15,7 @@ use rustc_hash::{FxHashMap, FxHashSet};
 
 use crate::Db;
 use crate::place::Place;
+use crate::semantic_index::definition::Definition;
 use crate::types::class::{ClassLiteral, ClassType, GenericAlias};
 use crate::types::function::{FunctionType, OverloadLiteral};
 use crate::types::generics::{GenericContext, Specialization};
@@ -40,6 +41,9 @@ pub struct DisplaySettings<'db> {
     pub qualified: Rc<FxHashMap<&'db str, QualificationLevel>>,
     /// Whether long unions and literals are displayed in full
     pub preserve_full_unions: bool,
+    /// Disallow Signature printing to introduce a name
+    /// (presumably because we rendered one already)
+    pub disallow_signature_name: bool,
 }
 
 impl<'db> DisplaySettings<'db> {
@@ -75,6 +79,14 @@ impl<'db> DisplaySettings<'db> {
         }
     }
 
+    #[must_use]
+    pub fn disallow_signature_name(&self) -> Self {
+        Self {
+            disallow_signature_name: true,
+            ..self.clone()
+        }
+    }
+
     #[must_use]
     pub fn from_possibly_ambiguous_types<I, T>(db: &'db dyn Db, types: I) -> Self
     where
@@ -745,7 +757,7 @@ impl<'db> FmtDetailed<'db> for DisplayRepresentation<'db> {
                         type_parameters.fmt_detailed(f)?;
                         signature
                             .bind_self(self.db, Some(typing_self_ty))
-                            .display_with(self.db, self.settings.clone())
+                            .display_with(self.db, self.settings.disallow_signature_name())
                             .fmt_detailed(f)
                     }
                     signatures => {
@@ -1161,7 +1173,7 @@ impl<'db> FmtDetailed<'db> for DisplayOverloadLiteral<'db> {
         write!(f, "{}", self.literal.name(self.db))?;
         type_parameters.fmt_detailed(f)?;
         signature
-            .display_with(self.db, self.settings.clone())
+            .display_with(self.db, self.settings.disallow_signature_name())
             .fmt_detailed(f)
     }
 }
@@ -1208,7 +1220,7 @@ impl<'db> FmtDetailed<'db> for DisplayFunctionType<'db> {
                 write!(f, "{}", self.ty.name(self.db))?;
                 type_parameters.fmt_detailed(f)?;
                 signature
-                    .display_with(self.db, self.settings.clone())
+                    .display_with(self.db, self.settings.disallow_signature_name())
                     .fmt_detailed(f)
             }
             signatures => {
@@ -1627,6 +1639,7 @@ impl<'db> Signature<'db> {
         settings: DisplaySettings<'db>,
     ) -> DisplaySignature<'a, 'db> {
         DisplaySignature {
+            definition: self.definition(),
             parameters: self.parameters(),
             return_ty: self.return_ty,
             db,
@@ -1636,6 +1649,7 @@ impl<'db> Signature<'db> {
 }
 
 pub(crate) struct DisplaySignature<'a, 'db> {
+    definition: Option<Definition<'db>>,
     parameters: &'a Parameters<'db>,
     return_ty: Option<Type<'db>>,
     db: &'db dyn Db,
@@ -1663,6 +1677,17 @@ impl<'db> FmtDetailed<'db> for DisplaySignature<'_, 'db> {
         // When we exit this function, write a marker signaling we're ending a signature
         let mut f = f.with_detail(TypeDetail::SignatureEnd);
 
+        // If we're multiline printing and a name hasn't been emitted, try to
+        // remember what the name was by checking if we have a definition
+        if self.settings.multiline
+            && !self.settings.disallow_signature_name
+            && let Some(definition) = self.definition
+            && let Some(name) = definition.name(self.db)
+        {
+            f.write_str("def ")?;
+            f.write_str(&name)?;
+        }
+
         // Parameters
         self.parameters
             .display_with(self.db, self.settings.clone())

crates/ty_python_semantic/src/types/generics.rs

@@ -1586,8 +1586,8 @@ impl<'db> SpecializationBuilder<'db> {
     ) {
         #[derive(Default)]
         struct Bounds<'db> {
-            lower: Vec<Type<'db>>,
-            upper: Vec<Type<'db>>,
+            lower: FxOrderSet<Type<'db>>,
+            upper: FxOrderSet<Type<'db>>,
         }
 
         let constraints = constraints.limit_to_valid_specializations(self.db);
@@ -1611,17 +1611,17 @@ impl<'db> SpecializationBuilder<'db> {
                 let lower = constraint.lower(self.db);
                 let upper = constraint.upper(self.db);
                 let bounds = mappings.entry(typevar).or_default();
-                bounds.lower.push(lower);
-                bounds.upper.push(upper);
+                bounds.lower.insert(lower);
+                bounds.upper.insert(upper);
 
                 if let Type::TypeVar(lower_bound_typevar) = lower {
                     let bounds = mappings.entry(lower_bound_typevar).or_default();
-                    bounds.upper.push(Type::TypeVar(typevar));
+                    bounds.upper.insert(Type::TypeVar(typevar));
                 }
 
                 if let Type::TypeVar(upper_bound_typevar) = upper {
                     let bounds = mappings.entry(upper_bound_typevar).or_default();
-                    bounds.lower.push(Type::TypeVar(typevar));
+                    bounds.lower.insert(Type::TypeVar(typevar));
                 }
             }
 

crates/ty_python_semantic/src/types/infer/builder.rs

@@ -2358,12 +2358,16 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
             decorator_types_and_nodes.push((decorator_type, decorator));
         }
 
+        // In stub files, default values may reference names that are defined later in the file.
+        let in_stub = self.in_stub();
+        let previous_deferred_state = std::mem::replace(&mut self.deferred_state, in_stub.into());
         for default in parameters
             .iter_non_variadic_params()
             .filter_map(|param| param.default.as_deref())
         {
             self.infer_expression(default, TypeContext::default());
         }
+        self.deferred_state = previous_deferred_state;
 
         // If there are type params, parameters and returns are evaluated in that scope. Otherwise,
         // we always defer the inference of the parameters and returns. That ensures that we do not
@@ -2998,9 +3002,14 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
         // if there are type parameters, then the keywords and bases are within that scope
         // and we don't need to run inference here
         if type_params.is_none() {
+            // In stub files, keyword values may reference names that are defined later in the file.
+            let in_stub = self.in_stub();
+            let previous_deferred_state =
+                std::mem::replace(&mut self.deferred_state, in_stub.into());
             for keyword in class_node.keywords() {
                 self.infer_expression(&keyword.value, TypeContext::default());
             }
+            self.deferred_state = previous_deferred_state;
 
             // Inference of bases deferred in stubs, or if any are string literals.
             if self.in_stub() || class_node.bases().iter().any(contains_string_literal) {
@@ -8322,6 +8331,10 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
             body: _,
         } = lambda_expression;
 
+        // In stub files, default values may reference names that are defined later in the file.
+        let in_stub = self.in_stub();
+        let previous_deferred_state = std::mem::replace(&mut self.deferred_state, in_stub.into());
+
         let parameters = if let Some(parameters) = parameters {
             let positional_only = parameters
                 .posonlyargs
@@ -8387,6 +8400,8 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
             Parameters::empty()
         };
 
+        self.deferred_state = previous_deferred_state;
+
         // TODO: Useful inference of a lambda's return type will require a different approach,
         // which does the inference of the body expression based on arguments at each call site,
         // rather than eagerly computing a return type without knowing the argument types.

crates/ty_python_semantic/src/types/narrow.rs

@@ -459,6 +459,82 @@ impl<'db, 'ast> NarrowingConstraintsBuilder<'db, 'ast> {
             .expect("We should always have a place for every `PlaceExpr`")
     }
 
+    /// Check if a type is directly narrowable by `len()` (without considering unions or intersections).
+    ///
+    /// These are types where we know `__bool__` and `__len__` are consistent and the type
+    /// cannot be subclassed with a `__bool__` that disagrees.
+    fn is_base_type_narrowable_by_len(db: &'db dyn Db, ty: Type<'db>) -> bool {
+        match ty {
+            Type::StringLiteral(_) | Type::LiteralString | Type::BytesLiteral(_) => true,
+            Type::NominalInstance(instance) => instance.tuple_spec(db).is_some(),
+            _ => false,
+        }
+    }
+
+    /// Narrow a type based on `len()`, only narrowing the parts that are safe to narrow.
+    ///
+    /// For narrowable types (literals, tuples), we apply `~AlwaysFalsy` (positive) or
+    /// `~AlwaysTruthy` (negative). For non-narrowable types, we return them unchanged.
+    ///
+    /// Returns `None` if no part of the type is narrowable.
+    fn narrow_type_by_len(db: &'db dyn Db, ty: Type<'db>, is_positive: bool) -> Option<Type<'db>> {
+        match ty {
+            Type::Union(union) => {
+                let mut has_narrowable = false;
+                let narrowed_elements: Vec<_> = union
+                    .elements(db)
+                    .iter()
+                    .map(|element| {
+                        if let Some(narrowed) = Self::narrow_type_by_len(db, *element, is_positive)
+                        {
+                            has_narrowable = true;
+                            narrowed
+                        } else {
+                            // Non-narrowable elements are kept unchanged.
+                            *element
+                        }
+                    })
+                    .collect();
+
+                if has_narrowable {
+                    Some(UnionType::from_elements(db, narrowed_elements))
+                } else {
+                    None
+                }
+            }
+            Type::Intersection(intersection) => {
+                // For intersections, check if any positive element is narrowable.
+                let positive = intersection.positive(db);
+                let has_narrowable = positive
+                    .iter()
+                    .any(|element| Self::is_base_type_narrowable_by_len(db, *element));
+
+                if has_narrowable {
+                    // Apply the narrowing constraint to the whole intersection.
+                    let mut builder = IntersectionBuilder::new(db).add_positive(ty);
+                    if is_positive {
+                        builder = builder.add_negative(Type::AlwaysFalsy);
+                    } else {
+                        builder = builder.add_negative(Type::AlwaysTruthy);
+                    }
+                    Some(builder.build())
+                } else {
+                    None
+                }
+            }
+            _ if Self::is_base_type_narrowable_by_len(db, ty) => {
+                let mut builder = IntersectionBuilder::new(db).add_positive(ty);
+                if is_positive {
+                    builder = builder.add_negative(Type::AlwaysFalsy);
+                } else {
+                    builder = builder.add_negative(Type::AlwaysTruthy);
+                }
+                Some(builder.build())
+            }
+            _ => None,
+        }
+    }
+
     fn evaluate_simple_expr(
         &mut self,
         expr: &ast::Expr,
@@ -901,6 +977,27 @@ impl<'db, 'ast> NarrowingConstraintsBuilder<'db, 'ast> {
                     guarded_ty.negate_if(self.db, !is_positive),
                 )]))
             }
+            // For the expression `len(E)`, we narrow the type based on whether len(E) is truthy
+            // (i.e., whether E is non-empty). We only narrow the parts of the type where we know
+            // `__bool__` and `__len__` are consistent (literals, tuples). Non-narrowable parts
+            // (str, list, etc.) are kept unchanged.
+            Type::FunctionLiteral(function_type)
+                if expr_call.arguments.args.len() == 1
+                    && expr_call.arguments.keywords.is_empty()
+                    && function_type.known(self.db) == Some(KnownFunction::Len) =>
+            {
+                let arg = &expr_call.arguments.args[0];
+                let arg_ty = inference.expression_type(arg);
+
+                // Narrow only the parts of the type that are safe to narrow based on len().
+                if let Some(narrowed_ty) = Self::narrow_type_by_len(self.db, arg_ty, is_positive) {
+                    let target = place_expr(arg)?;
+                    let place = self.expect_place(&target);
+                    Some(NarrowingConstraints::from_iter([(place, narrowed_ty)]))
+                } else {
+                    None
+                }
+            }
             Type::FunctionLiteral(function_type) if expr_call.arguments.keywords.is_empty() => {
                 let [first_arg, second_arg] = &*expr_call.arguments.args else {
                     return None;

docs/editors/setup.md

@@ -375,7 +375,7 @@ Starting with version 2025.3, PyCharm supports Ruff out of the box:
 
 1. Select which options should be enabled.
 
-For more information, refer to [PyCharm documentation](https://www.jetbrains.com/help/pycharm/2025.3/lsp-tools.html#ruff).
+For more information, refer to [PyCharm documentation](https://www.jetbrains.com/help/pycharm/lsp-tools.html#ruff).
 
 ### Via External Tool
 

ruff.schema.json

@@ -3482,6 +3482,7 @@
         "ISC001",
         "ISC002",
         "ISC003",
+        "ISC004",
         "LOG",
         "LOG0",
         "LOG00",