From 2dc2f68b0f48a18ff038d9aadeb07ca8ca73a085 Mon Sep 17 00:00:00 2001
From: Dan Parizher <105245560+danparizher@users.noreply.github.com>
Date: Fri, 15 Aug 2025 15:09:55 -0400
Subject: [PATCH] [`pycodestyle`] Make `E731` fix unsafe instead of
 display-only for class assignments (#19700)

## Summary

Fixes #19650

---------

Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>
---
 .../pycodestyle/rules/lambda_assignment.rs    | 35 ++++++++-----------
 ...les__pycodestyle__tests__E731_E731.py.snap | 12 +++----
 2 files changed, 21 insertions(+), 26 deletions(-)

diff --git a/crates/ruff_linter/src/rules/pycodestyle/rules/lambda_assignment.rs b/crates/ruff_linter/src/rules/pycodestyle/rules/lambda_assignment.rs
index c8cbc21ce6..24c47e1c7c 100644
--- a/crates/ruff_linter/src/rules/pycodestyle/rules/lambda_assignment.rs
+++ b/crates/ruff_linter/src/rules/pycodestyle/rules/lambda_assignment.rs
@@ -10,7 +10,7 @@ use ruff_source_file::UniversalNewlines;
 use ruff_text_size::{Ranged, TextRange};
 
 use crate::checkers::ast::Checker;
-use crate::{Edit, Fix, FixAvailability, Violation};
+use crate::{Applicability, Edit, Fix, FixAvailability, Violation};
 
 /// ## What it does
 /// Checks for lambda expressions which are assigned to a variable.
@@ -105,29 +105,24 @@ pub(crate) fn lambda_assignment(
             }
         }
 
-        // Otherwise, if the assignment is in a class body, flag it, but use a display-only fix.
-        // Rewriting safely would require making this a static method.
-        //
-        // Similarly, if the lambda is shadowing a variable in the current scope,
+        // If the lambda is shadowing a variable in the current scope,
         // rewriting it as a function declaration may break type-checking.
         // See: https://github.com/astral-sh/ruff/issues/5421
-        if checker.semantic().current_scope().kind.is_class()
-            || checker
-                .semantic()
-                .current_scope()
-                .get_all(id)
-                .any(|binding_id| checker.semantic().binding(binding_id).kind.is_annotation())
+        let applicability = if checker
+            .semantic()
+            .current_scope()
+            .get_all(id)
+            .any(|binding_id| checker.semantic().binding(binding_id).kind.is_annotation())
         {
-            diagnostic.set_fix(Fix::display_only_edit(Edit::range_replacement(
-                indented,
-                stmt.range(),
-            )));
+            Applicability::DisplayOnly
         } else {
-            diagnostic.set_fix(Fix::unsafe_edit(Edit::range_replacement(
-                indented,
-                stmt.range(),
-            )));
-        }
+            Applicability::Unsafe
+        };
+
+        diagnostic.set_fix(Fix::applicable_edit(
+            Edit::range_replacement(indented, stmt.range()),
+            applicability,
+        ));
     }
 }
 
diff --git a/crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E731_E731.py.snap b/crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E731_E731.py.snap
index 9b7e9c54c8..f3054605a4 100644
--- a/crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E731_E731.py.snap
+++ b/crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E731_E731.py.snap
@@ -105,7 +105,7 @@ help: Rewrite `f` as a `def`
 26 27 | 
 27 28 | def scope():
 
-E731 Do not assign a `lambda` expression, use a `def`
+E731 [*] Do not assign a `lambda` expression, use a `def`
   --> E731.py:57:5
    |
 55 | class Scope:
@@ -115,7 +115,7 @@ E731 Do not assign a `lambda` expression, use a `def`
    |
 help: Rewrite `f` as a `def`
 
-ℹ Display-only fix
+ℹ Unsafe fix
 54 54 | 
 55 55 | class Scope:
 56 56 |     # E731
@@ -318,7 +318,7 @@ help: Rewrite `f` as a `def`
 137 138 | 
 138 139 | class TemperatureScales(Enum):
 
-E731 Do not assign a `lambda` expression, use a `def`
+E731 [*] Do not assign a `lambda` expression, use a `def`
    --> E731.py:139:5
     |
 138 | class TemperatureScales(Enum):
@@ -328,7 +328,7 @@ E731 Do not assign a `lambda` expression, use a `def`
     |
 help: Rewrite `CELSIUS` as a `def`
 
-ℹ Display-only fix
+ℹ Unsafe fix
 136 136 | 
 137 137 | 
 138 138 | class TemperatureScales(Enum):
@@ -339,7 +339,7 @@ help: Rewrite `CELSIUS` as a `def`
 141 142 | 
 142 143 | 
 
-E731 Do not assign a `lambda` expression, use a `def`
+E731 [*] Do not assign a `lambda` expression, use a `def`
    --> E731.py:140:5
     |
 138 | class TemperatureScales(Enum):
@@ -349,7 +349,7 @@ E731 Do not assign a `lambda` expression, use a `def`
     |
 help: Rewrite `FAHRENHEIT` as a `def`
 
-ℹ Display-only fix
+ℹ Unsafe fix
 137 137 | 
 138 138 | class TemperatureScales(Enum):
 139 139 |     CELSIUS = (lambda deg_c: deg_c)