Apr 1, 2025 · Mar 30, 2025 · Mar 30, 2025 · Mar 30, 2025 · Mar 30, 2025 · Mar 31, 2025
diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py

        # Check for too many or few values for formals.
        for i, kind in enumerate(callee.arg_kinds):
            if kind.is_required() and not formal_to_actual[i] and not is_unexpected_arg_error:
            mapped_args = formal_to_actual[i]
            if kind.is_required() and not mapped_args and not is_unexpected_arg_error:
                # No actual for a mandatory formal
                if kind.is_positional():
                    self.msg.too_few_arguments(callee, context, actual_names)
                    self.msg.missing_named_argument(callee, context, argname)
                ok = False
            elif not kind.is_star() and is_duplicate_mapping(
 formal_to_actual[i], actual_types, actual_kinds
 mapped_args, actual_types, actual_kinds
            ):
                if self.chk.in_checked_function() or isinstance(
                    get_proper_type(actual_types[formal_to_actual[i][0]]), TupleType
                    get_proper_type(actual_types[mapped_args[0]]), TupleType
                ):
                    self.msg.duplicate_argument_value(callee, i, context)
                    ok = False
            elif (
                kind.is_named()
                andformal_to_actual[i]
                and actual_kinds[formal_to_actual[i][0]] not in [nodes.ARG_NAMED, nodes.ARG_STAR2]
                andmapped_args
                and actual_kinds[mapped_args[0]] not in [nodes.ARG_NAMED, nodes.ARG_STAR2]
            ):
                # Positional argument when expecting a keyword argument.
                self.msg.too_many_positional_arguments(callee, context)
                ok = False
            elif (
                callee.param_spec() is not None
                and not formal_to_actual[i]
                and callee.special_sig != "partial"
            ):
                self.msg.too_few_arguments(callee, context, actual_names)
                ok = False
            elif callee.param_spec() is not None:
                if not mapped_args and callee.special_sig != "partial":
                    self.msg.too_few_arguments(callee, context, actual_names)
                    ok = False
                elif len(mapped_args) > 1:
                    if actual_kinds[mapped_args[0]] == nodes.ARG_STAR:
                        self.msg.fail("ParamSpec.args should only be passed once", context)
                        ok = False
                    if actual_kinds[mapped_args[0]] == nodes.ARG_STAR2:
                        self.msg.fail("ParamSpec.kwargs should only be passed once", context)
                        ok = False
        return ok

    def check_for_extra_actual_arguments(
diff --git a/test-data/unit/check-parameter-specification.test b/test-data/unit/check-parameter-specification.test

 reveal_type(fn(ServerErrorMiddleware))  # N: Revealed type is "__main__.Capture[[handler: Union[builtins.str, None] =, debug: builtins.bool =]]"
 [builtins fixtures/paramspec.pyi]

 [case testRunParamSpecDuplicateArgsKwargs]
 from typing_extensions import ParamSpec, Concatenate
 from typing import Callable

 _P = ParamSpec("_P")

 def run(predicate: Callable[_P, None], *args: _P.args, **kwargs: _P.kwargs) -> None:
    predicate(*args, *args, **kwargs)  # E: ParamSpec.args should only be passed once
    predicate(*args, **kwargs, **kwargs)  # E: ParamSpec.kwargs should only be passed once
    predicate(*args, *args, **kwargs, **kwargs)  # E: ParamSpec.args should only be passed once \
                                                 # E: ParamSpec.kwargs should only be passed once

 def run2(predicate: Callable[Concatenate[int, _P], None], *args: _P.args, **kwargs: _P.kwargs) -> None:
    predicate(*args, *args, **kwargs)  # E: ParamSpec.args should only be passed once \
                                       # E: Argument 1 has incompatible type "*_P.args"; expected "int"
    predicate(*args, **kwargs, **kwargs)  # E: ParamSpec.kwargs should only be passed once \
                                          # E: Argument 1 has incompatible type "*_P.args"; expected "int"
    predicate(1, *args, *args, **kwargs)  # E: ParamSpec.args should only be passed once
    predicate(1, *args, **kwargs, **kwargs)  # E: ParamSpec.kwargs should only be passed once
    predicate(1, *args, *args, **kwargs, **kwargs)  # E: ParamSpec.args should only be passed once \
                                                    # E: ParamSpec.kwargs should only be passed once
 [builtins fixtures/paramspec.pyi]
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2357,7 +2357,8 @@ def check_argument_count(

		# Check for too many or few values for formals.
		for i, kind in enumerate(callee.arg_kinds):
		if kind.is_required() and not formal_to_actual[i] and not is_unexpected_arg_error:
		mapped_args = formal_to_actual[i]
		if kind.is_required() and not mapped_args and not is_unexpected_arg_error:
		# No actual for a mandatory formal
		if kind.is_positional():
		self.msg.too_few_arguments(callee, context, actual_names)
Expand All		@@ -2368,28 +2369,32 @@ def check_argument_count(
		self.msg.missing_named_argument(callee, context, argname)
		ok = False
		elif not kind.is_star() and is_duplicate_mapping(
		formal_to_actual[i], actual_types, actual_kinds
		mapped_args, actual_types, actual_kinds
		):
		if self.chk.in_checked_function() or isinstance(
		get_proper_type(actual_types[formal_to_actual[i][0]]), TupleType
		get_proper_type(actual_types[mapped_args[0]]), TupleType
		):
		self.msg.duplicate_argument_value(callee, i, context)
		ok = False
		elif (
		kind.is_named()
		andformal_to_actual[i]
		and actual_kinds[formal_to_actual[i][0]] not in [nodes.ARG_NAMED, nodes.ARG_STAR2]
		andmapped_args
		and actual_kinds[mapped_args[0]] not in [nodes.ARG_NAMED, nodes.ARG_STAR2]
		):
		# Positional argument when expecting a keyword argument.
		self.msg.too_many_positional_arguments(callee, context)
		ok = False
		elif (
		callee.param_spec() is not None
		and not formal_to_actual[i]
		and callee.special_sig != "partial"
		):
		self.msg.too_few_arguments(callee, context, actual_names)
		ok = False
		elif callee.param_spec() is not None:
		if not mapped_args and callee.special_sig != "partial":
		self.msg.too_few_arguments(callee, context, actual_names)
		ok = False
		elif len(mapped_args) > 1:
		if actual_kinds[mapped_args[0]] == nodes.ARG_STAR:
		self.msg.fail("ParamSpec.args should only be passed once", context)
		ok = False
		if actual_kinds[mapped_args[0]] == nodes.ARG_STAR2:
		self.msg.fail("ParamSpec.kwargs should only be passed once", context)
		ok = False
		return ok

		def check_for_extra_actual_arguments(
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2560,3 +2560,26 @@ def fn(f: MiddlewareFactory[P]) -> Capture[P]: ...

		reveal_type(fn(ServerErrorMiddleware)) # N: Revealed type is "__main__.Capture[[handler: Union[builtins.str, None] =, debug: builtins.bool =]]"
		[builtins fixtures/paramspec.pyi]

		[case testRunParamSpecDuplicateArgsKwargs]
		from typing_extensions import ParamSpec, Concatenate
		from typing import Callable

		_P = ParamSpec("_P")

		def run(predicate: Callable[_P, None], args: _P.args, *kwargs: _P.kwargs) -> None:
		predicate(args, args, **kwargs) # E: ParamSpec.args should only be passed once
		predicate(args, kwargs, *kwargs) # E: ParamSpec.kwargs should only be passed once
		predicate(args, args, kwargs, kwargs) # E: ParamSpec.args should only be passed once \
		# E: ParamSpec.kwargs should only be passed once
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		def run2(predicate: Callable[Concatenate[int, _P], None], args: _P.args, *kwargs: _P.kwargs) -> None:
		predicate(args, args, **kwargs) # E: ParamSpec.args should only be passed once \
		# E: Argument 1 has incompatible type "*_P.args"; expected "int"
		predicate(args, kwargs, *kwargs) # E: ParamSpec.kwargs should only be passed once \
		# E: Argument 1 has incompatible type "*_P.args"; expected "int"
		predicate(1, args, args, **kwargs) # E: ParamSpec.args should only be passed once
		predicate(1, args, kwargs, *kwargs) # E: ParamSpec.kwargs should only be passed once
		predicate(1, args, args, kwargs, kwargs) # E: ParamSpec.args should only be passed once \
		# E: ParamSpec.kwargs should only be passed once
		[builtins fixtures/paramspec.pyi]