Fix function containing PEP 593 Annotated with a string literal second arg causing 'Name "x" is not defined" error (#10777)

Fixes #9868

When analyzing function definitions, mypy attempts to infer type variables. The code which did that also tried to look into the second type arg to `Annotated`, which, if a string literal, resulted in a lookup which may cause a 'Name "x" is not defined" error.

Co-authored-by: 97littleleaf11 <97littleleaf11@users.noreply.github.com>
Co-authored-by: Jingchen Ye <97littleleaf11@gmail.com>

Author: syastrov

mypy/typeanal.py

@@ -1269,6 +1269,9 @@ def visit_unbound_type(self, t: UnboundType) -> TypeVarLikeList:
             return []
         elif node and node.fullname in ('typing_extensions.Literal', 'typing.Literal'):
             return []
+        elif node and node.fullname in ('typing_extensions.Annotated', 'typing.Annotated'):
+            # Don't query the second argument to Annotated for TypeVars
+            return self.query_types([t.args[0]])
         else:
             return super().visit_unbound_type(t)
 

test-data/unit/check-annotated.test

@@ -127,19 +127,33 @@ x = Annotated[int, Meta()]
 reveal_type(x)  # N: Revealed type is "def () -> builtins.int"
 [builtins fixtures/tuple.pyi]
 
+[case testAnnotatedStringLiteralInFunc]
+from typing import TypeVar
+from typing_extensions import Annotated
+def f1(a: Annotated[str, "metadata"]):
+    pass
+reveal_type(f1)  # N: Revealed type is "def (a: builtins.str) -> Any"
+def f2(a: Annotated["str", "metadata"]):
+    pass
+reveal_type(f2)  # N: Revealed type is "def (a: builtins.str) -> Any"
+def f3(a: Annotated["notdefined", "metadata"]): # E: Name "notdefined" is not defined
+    pass
+T = TypeVar('T')
+def f4(a: Annotated[T, "metatdata"]):
+    pass
+reveal_type(f4)  # N: Revealed type is "def [T] (a: T`-1) -> Any"
+[builtins fixtures/tuple.pyi]
+
 [case testSliceAnnotated39]
 # flags: --python-version 3.9
 from typing_extensions import Annotated
-
 a: Annotated[int, 1:2]
 reveal_type(a)  # N: Revealed type is "builtins.int"
-
 [builtins fixtures/tuple.pyi]
+
 [case testSliceAnnotated38]
 # flags: --python-version 3.8
 from typing_extensions import Annotated
-
 a: Annotated[int, 1:2]
 reveal_type(a)  # N: Revealed type is "builtins.int"
-
 [builtins fixtures/tuple.pyi]