Make lambda-assignment fix always-manual in class bodies

crates/ruff/resources/test/fixtures/pycodestyle/E731.py

@@ -133,3 +133,8 @@ def scope():
     from collections.abc import Callable
 
     f: Callable[[str, int, list[str]], list[str]] = lambda a, b, /, c: [*c, a * b]
+
+
+class TemperatureScales(Enum):
+    CELSIUS = (lambda deg_c: deg_c)
+    FAHRENHEIT = (lambda deg_c: deg_c * 9 / 5 + 32)

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

@@ -112,11 +112,14 @@ pub(crate) fn lambda_assignment(
             // If the assignment is in a class body, it might not be safe to replace it because the
             // assignment might be carrying a type annotation that will be used by some package like
             // dataclasses, which wouldn't consider the rewritten function definition to be
-            // equivalent. Similarly, if the lambda is shadowing a variable in the current scope,
-            // rewriting it as a function declaration may break type-checking.
+            // equivalent. Even if it _doesn't_ have an annotation, rewriting safely would require
+            // making this a static method.
             // See: https://github.com/astral-sh/ruff/issues/3046
+            //
+            // Similarly, 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 (annotation.is_some() && checker.semantic().current_scope().kind.is_class())
+            if checker.semantic().current_scope().kind.is_class()
                 || checker
                     .semantic()
                     .current_scope()

crates/ruff/src/rules/pycodestyle/snapshots/ruff__rules__pycodestyle__tests__E731_E731.py.snap

@@ -109,7 +109,7 @@ E731.py:57:5: E731 [*] Do not assign a `lambda` expression, use a `def`
    |
    = help: Rewrite `f` as a `def`
 
-ℹ Suggested fix
+ℹ Possible fix
 54 54 | 
 55 55 | class Scope:
 56 56 |     # E731
@@ -318,5 +318,43 @@ E731.py:135:5: E731 [*] Do not assign a `lambda` expression, use a `def`
 135     |-    f: Callable[[str, int, list[str]], list[str]] = lambda a, b, /, c: [*c, a * b]
     135 |+    def f(a: str, b: int, /, c: list[str]) -> list[str]:
     136 |+        return [*c, a * b]
+136 137 | 
+137 138 | 
+138 139 | class TemperatureScales(Enum):
+
+E731.py:139:5: E731 [*] Do not assign a `lambda` expression, use a `def`
+    |
+138 | class TemperatureScales(Enum):
+139 |     CELSIUS = (lambda deg_c: deg_c)
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ E731
+140 |     FAHRENHEIT = (lambda deg_c: deg_c * 9 / 5 + 32)
+    |
+    = help: Rewrite `CELSIUS` as a `def`
+
+ℹ Possible fix
+136 136 | 
+137 137 | 
+138 138 | class TemperatureScales(Enum):
+139     |-    CELSIUS = (lambda deg_c: deg_c)
+    139 |+    def CELSIUS(deg_c):
+    140 |+        return deg_c
+140 141 |     FAHRENHEIT = (lambda deg_c: deg_c * 9 / 5 + 32)
+
+E731.py:140:5: E731 [*] Do not assign a `lambda` expression, use a `def`
+    |
+138 | class TemperatureScales(Enum):
+139 |     CELSIUS = (lambda deg_c: deg_c)
+140 |     FAHRENHEIT = (lambda deg_c: deg_c * 9 / 5 + 32)
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ E731
+    |
+    = help: Rewrite `FAHRENHEIT` as a `def`
+
+ℹ Possible fix
+137 137 | 
+138 138 | class TemperatureScales(Enum):
+139 139 |     CELSIUS = (lambda deg_c: deg_c)
+140     |-    FAHRENHEIT = (lambda deg_c: deg_c * 9 / 5 + 32)
+    140 |+    def FAHRENHEIT(deg_c):
+    141 |+        return deg_c * 9 / 5 + 32