[pyflakes] Fix false positive for __class__ in lambda expressions within class definitions (F821)

[danparizher]

Summary

Fixes #20562

[github-actions]

ruff-ecosystem results

Linter (stable)

ℹ️ ecosystem check detected linter changes. (+3 -0 violations, +0 -0 fixes in 2 projects; 53 projects unchanged)

apache/airflow (+1 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --no-preview --select ALL

+ task-sdk/src/airflow/sdk/execution_time/comms.py:56:20: TC003 Move standard library import `socket.socket` into a type-checking block

langchain-ai/langchain (+2 -0 violations, +0 -0 fixes)

+ libs/langchain/langchain/indexes/_sql_record_manager.py:19:8: F401 [*] `uuid` imported but unused
+ libs/langchain/langchain/indexes/_sql_record_manager.py:62:5: F811 Redefinition of unused `uuid` from line 19: `uuid` redefined here

Changes by rule (3 rules affected)

code	total	+ violation	- violation	+ fix	- fix
TC003	1	1	0	0	0
F401	1	1	0	0	0
F811	1	1	0	0	0

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+3 -0 violations, +0 -0 fixes in 2 projects; 53 projects unchanged)

apache/airflow (+1 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview --select ALL

+ task-sdk/src/airflow/sdk/execution_time/comms.py:56:20: TC003 Move standard library import `socket.socket` into a type-checking block

langchain-ai/langchain (+2 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

+ libs/langchain/langchain/indexes/_sql_record_manager.py:19:8: F401 [*] `uuid` imported but unused
+ libs/langchain/langchain/indexes/_sql_record_manager.py:62:5: F811 Redefinition of unused `uuid` from line 19: `uuid` redefined here

Changes by rule (3 rules affected)

code	total	+ violation	- violation	+ fix	- fix
TC003	1	1	0	0	0
F401	1	1	0	0	0
F811	1	1	0	0	0

[ntBre]

Thank you! The tests look good, but what do you think about moving the new code to visit_expr to mirror the function version a bit more closely?

[ntBre]

I was picturing this in visit_stmt like we did for function definitions rather than in the deferred visit. I guess lambdas aren't statements, so the analogous code would actually fit here in visit_expr:

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

Lines 1620 to 1632 in e4ac9e9

	// Visit the default arguments, but avoid the body, which will be deferred.
	if let Some(parameters) = parameters {
	for default in parameters
	.iter_non_variadic_params()
	.filter_map(|param| param.default.as_deref())
	{
	self.visit_expr(default);
	}
	}
	self.semantic.push_scope(ScopeKind::Lambda(lambda));
	self.visit.lambdas.push(self.semantic.snapshot());
	self.analyze.lambdas.push(self.semantic.snapshot());

I think that should work because we push a lambda snapshot that gets used here like we do for functions. The one downside is that the popping for lambdas happens a bit farther down, unlike functions:

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

Lines 2062 to 2063 in e4ac9e9

	self.analyze.scopes.push(self.semantic.scope_id);
	self.semantic.pop_scope();

[danparizher]

Yeah, that approach makes sense to me. Thanks for the review!