Use "parameter" instead of "argument" in unpacking error (#20683)

Fixes #20679

Author: hyperkai

mypy/semanal.py

@@ -1104,7 +1104,7 @@ def remove_unpack_kwargs(self, defn: FuncDef, typ: CallableType) -> CallableType
             return typ
         p_last_type = get_proper_type(last_type.type)
         if not isinstance(p_last_type, TypedDictType):
-            self.fail("Unpack item in ** argument must be a TypedDict", last_type)
+            self.fail("Unpack item in ** parameter must be a TypedDict", last_type)
             new_arg_types = typ.arg_types[:-1] + [AnyType(TypeOfAny.from_error)]
             return typ.copy_modified(arg_types=new_arg_types)
         overlap = set(typ.arg_names) & set(p_last_type.items)

test-data/unit/check-typevar-tuple.test

@@ -2191,15 +2191,15 @@ g(1, 2, 3)  # E: Missing named argument "a" for "g" \
 
 def bad(
     *args: Unpack[Keywords],  # E: "Keywords" cannot be unpacked (must be tuple or TypeVarTuple)
-    **kwargs: Unpack[Ints],  # E: Unpack item in ** argument must be a TypedDict
+    **kwargs: Unpack[Ints],  # E: Unpack item in ** parameter must be a TypedDict
 ) -> None: ...
 reveal_type(bad)  # N: Revealed type is "def (*args: Any, **kwargs: Any)"
 
 def bad2(
     one: int,
     *args: Unpack[Keywords],  # E: "Keywords" cannot be unpacked (must be tuple or TypeVarTuple)
     other: str = "no",
-     **kwargs: Unpack[Ints],  # E: Unpack item in ** argument must be a TypedDict
+     **kwargs: Unpack[Ints],  # E: Unpack item in ** parameter must be a TypedDict
 ) -> None: ...
 reveal_type(bad2)  # N: Revealed type is "def (one: builtins.int, *args: Any, other: builtins.str =, **kwargs: Any)"
 [builtins fixtures/dict.pyi]

test-data/unit/check-varargs.test

@@ -792,7 +792,7 @@ def baz(**kwargs: Unpack[Person]) -> None:  # OK
 [case testUnpackWithoutTypedDict]
 from typing_extensions import Unpack
 
-def foo(**kwargs: Unpack[dict]) -> None:  # E: Unpack item in ** argument must be a TypedDict
+def foo(**kwargs: Unpack[dict]) -> None:  # E: Unpack item in ** parameter must be a TypedDict
     ...
 [builtins fixtures/dict.pyi]
 

test-data/unit/semanal-errors.test

@@ -1471,7 +1471,7 @@ class Variadic(Generic[Unpack[TVariadic], Unpack[TVariadic2]]):  # E: Can only u
 def bad_args(*args: TVariadic):  # E: TypeVarTuple "TVariadic" is only valid with an unpack
     pass
 
-def bad_kwargs(**kwargs: Unpack[TVariadic]):  # E: Unpack item in ** argument must be a TypedDict
+def bad_kwargs(**kwargs: Unpack[TVariadic]):  # E: Unpack item in ** parameter must be a TypedDict
     pass
 
 [builtins fixtures/dict.pyi]