Update error message for parameter overlap in TypedDict (#20956)

Fixes #20933

Author: hyperkai

mypy/semanal.py

@@ -1125,7 +1125,9 @@ def remove_unpack_kwargs(self, defn: FuncDef, typ: CallableType) -> CallableType
         overlap.discard(typ.arg_names[-1])
         if overlap:
             overlapped = ", ".join([f'"{name}"' for name in sorted(filter(None, overlap))])
-            self.fail(f"Overlap between argument names and ** TypedDict items: {overlapped}", defn)
+            self.fail(
+                f"Overlap between parameter names and ** TypedDict items: {overlapped}", defn
+            )
             new_arg_types = typ.arg_types[:-1] + [AnyType(TypeOfAny.from_error)]
             return typ.copy_modified(arg_types=new_arg_types)
         # OK, everything looks right now, mark the callable type as using unpack.

test-data/unit/check-varargs.test

@@ -803,7 +803,7 @@ from typing_extensions import Unpack
 class Person(TypedDict):
     name: str
     age: int
-def foo(name: str, **kwargs: Unpack[Person]) -> None:  # E: Overlap between argument names and ** TypedDict items: "name"
+def foo(name: str, **kwargs: Unpack[Person]) -> None:  # E: Overlap between parameter names and ** TypedDict items: "name"
     ...
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-typeddict.pyi]