Iterate over lambdas in deferred type annotations

crates/ruff_linter/resources/test/fixtures/pyflakes/F401_20.py

@@ -0,0 +1,4 @@
+import re
+from typing import Annotated
+
+type X = Annotated[int, lambda: re.compile("x")]

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

@@ -895,6 +895,7 @@ where
                     range: _,
                 },
             ) => {
+                println!("Lambda: {:?}", lambda);
                 // Visit the default arguments, but avoid the body, which will be deferred.
                 if let Some(parameters) = parameters {
                     for ParameterWithDefault {
@@ -1205,6 +1206,7 @@ where
                                     self.visit_expr(expr);
                                 }
                                 for expr in iter {
+                                    println!("Visiting non-type definition: {:?}", expr);
                                     self.visit_non_type_definition(expr);
                                 }
                                 self.visit_expr_context(ctx);
@@ -2013,13 +2015,15 @@ pub(crate) fn check_ast(
     // Iterate over the AST.
     checker.visit_body(python_ast);
 
-    // Visit any deferred syntax nodes.
+    // Visit any deferred syntax nodes. Take care to visit in order, such that we avoid adding
+    // new deferred nodes after visiting nodes of that kind. For example, visiting a deferred
+    // function can add a deferred lambda, but the opposite is not true.
     checker.visit_deferred_functions();
-    checker.visit_deferred_lambdas();
-    checker.visit_deferred_future_type_definitions();
     checker.visit_deferred_type_param_definitions();
+    checker.visit_deferred_future_type_definitions();
     let allocator = typed_arena::Arena::new();
     checker.visit_deferred_string_type_definitions(&allocator);
+    checker.visit_deferred_lambdas();
     checker.visit_exports();
 
     // Check docstrings, bindings, and unresolved references.

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

@@ -52,6 +52,7 @@ mod tests {
     #[test_case(Rule::UnusedImport, Path::new("F401_17.py"))]
     #[test_case(Rule::UnusedImport, Path::new("F401_18.py"))]
     #[test_case(Rule::UnusedImport, Path::new("F401_19.py"))]
+    #[test_case(Rule::UnusedImport, Path::new("F401_20.py"))]
     #[test_case(Rule::ImportShadowedByLoopVar, Path::new("F402.py"))]
     #[test_case(Rule::UndefinedLocalWithImportStar, Path::new("F403.py"))]
     #[test_case(Rule::LateFutureImport, Path::new("F404.py"))]

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F401_F401_20.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff_linter/src/rules/pyflakes/mod.rs
+---
+