Avoid false positive for undefined variables in FAST001 (#23224)

Closes #20945.

Author: charliermarsh

crates/ruff_linter/resources/test/fixtures/fastapi/FAST001.py

@@ -102,6 +102,11 @@ async def create_item(item: Item) -> Dict[str, str]:
     return item
 
 
+@app.post("/items/", response_model=Foo)
+async def create_item(item: Item) -> Foo:
+    return item
+
+
 app = None
 
 

crates/ruff_linter/src/rules/fastapi/rules/fastapi_redundant_response_model.rs

@@ -127,8 +127,13 @@ fn is_identical_types(
     if let (Expr::Name(response_mode_name_expr), Expr::Name(return_value_name_expr)) =
         (response_model_arg, return_value)
     {
-        return semantic.resolve_name(response_mode_name_expr)
-            == semantic.resolve_name(return_value_name_expr);
+        return semantic
+            .resolve_name(response_mode_name_expr)
+            .is_some_and(|left| {
+                semantic
+                    .resolve_name(return_value_name_expr)
+                    .is_some_and(|right| left == right)
+            });
     }
     if let (Expr::Subscript(response_mode_subscript), Expr::Subscript(return_value_subscript)) =
         (response_model_arg, return_value)

crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__deferred_annotations_diff_fast-api-redundant-response-model_FAST001.py.snap

@@ -192,22 +192,22 @@ note: This is an unsafe fix and may change runtime behavior
 
 
 FAST001 [*] FastAPI route with redundant `response_model` argument
-   --> FAST001.py:118:23
+   --> FAST001.py:123:23
     |
-116 | def setup_app(app_arg: FastAPI, non_app: str) -> None:
-117 |     # Error
-118 |     @app_arg.get("/", response_model=str)
+121 | def setup_app(app_arg: FastAPI, non_app: str) -> None:
+122 |     # Error
+123 |     @app_arg.get("/", response_model=str)
     |                       ^^^^^^^^^^^^^^^^^^
-119 |     async def get_root() -> str:
-120 |         return "Hello World!"
+124 |     async def get_root() -> str:
+125 |         return "Hello World!"
     |
 help: Remove argument
-115 | 
-116 | def setup_app(app_arg: FastAPI, non_app: str) -> None:
-117 |     # Error
+120 | 
+121 | def setup_app(app_arg: FastAPI, non_app: str) -> None:
+122 |     # Error
     -     @app_arg.get("/", response_model=str)
-118 +     @app_arg.get("/")
-119 |     async def get_root() -> str:
-120 |         return "Hello World!"
-121 | 
+123 +     @app_arg.get("/")
+124 |     async def get_root() -> str:
+125 |         return "Hello World!"
+126 | 
 note: This is an unsafe fix and may change runtime behavior