Fixes TypedDict crash with function definition (#11126)

Fixes #11079

Author: sobolevn

mypy/semanal_typeargs.py

@@ -7,7 +7,7 @@
 
 from typing import List, Optional, Set
 
-from mypy.nodes import TypeInfo, Context, MypyFile, FuncItem, ClassDef, Block
+from mypy.nodes import TypeInfo, Context, MypyFile, FuncItem, ClassDef, Block, FakeInfo
 from mypy.types import (
     Type, Instance, TypeVarType, AnyType, get_proper_types, TypeAliasType, get_proper_type
 )
@@ -66,6 +66,8 @@ def visit_instance(self, t: Instance) -> None:
         # Type argument counts were checked in the main semantic analyzer pass. We assume
         # that the counts are correct here.
         info = t.type
+        if isinstance(info, FakeInfo):
+            return  # https://github.com/python/mypy/issues/11079
         for (i, arg), tvar in zip(enumerate(t.args), info.defn.type_vars):
             if tvar.values:
                 if isinstance(arg, TypeVarType):

test-data/unit/check-typeddict.test

@@ -185,6 +185,19 @@ p = Point(x=42, y=1337, z='whatever')
 reveal_type(p)  # N: Revealed type is "TypedDict('__main__.Point', {'x': builtins.int, 'y': builtins.int, 'z': Any})"
 [builtins fixtures/dict.pyi]
 
+[case testCannotCreateTypedDictWithClassWithFunctionUsedToCrash]
+# https://github.com/python/mypy/issues/11079
+from typing import TypedDict
+class D(TypedDict):
+    y: int
+    def x(self, key: int):  # E: Invalid statement in TypedDict definition; expected "field_name: field_type"
+        pass
+
+d = D(y=1)
+reveal_type(d)  # N: Revealed type is "TypedDict('__main__.D', {'y': builtins.int})"
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-typeddict.pyi]
+
 [case testCanCreateTypedDictTypeWithUnderscoreItemName]
 from mypy_extensions import TypedDict
 Point = TypedDict('Point', {'x': int, 'y': int, '_fallback': object})