Sep 21, 2024 · Sep 13, 2024 · Sep 13, 2024
diff --git a/mypy/semanal.py b/mypy/semanal.py

        if has_param_spec and num_args == 1 and types:
            first_arg = get_proper_type(types[0])
            if not (
                len(types) == 1 and isinstance(first_arg, (Parameters, ParamSpecType, AnyType))
            ):
            single_any = len(types) == 1 and isinstance(first_arg, AnyType)
            if not (single_any or any(isinstance(t, (Parameters, ParamSpecType)) for t in types)):
                types = [Parameters(types, [ARG_POS] * len(types), [None] * len(types))]

        return types
diff --git a/test-data/unit/check-parameter-specification.test b/test-data/unit/check-parameter-specification.test
 reveal_type(c)  # N: Revealed type is "__main__.C[Any]"
 [builtins fixtures/paramspec.pyi]

 [case testParamSpecInheritNoCrashOnNested]
 from typing import Generic
 from typing_extensions import ParamSpec

 P = ParamSpec("P")
 class C(Generic[P]): ...
 class D(C[int, [int, str], str]): ... # E: Nested parameter specifications are not allowed
 [builtins fixtures/paramspec.pyi]

 [case testParamSpecConcatenateSelfType]
 from typing import Callable
 from typing_extensions import ParamSpec, Concatenate
Original file line number	Diff line number	Diff line change
Expand Up		@@ -5904,9 +5904,8 @@ def analyze_type_application_args(self, expr: IndexExpr) -> list[Type] \| None:

		if has_param_spec and num_args == 1 and types:
		first_arg = get_proper_type(types[0])
		if not (
		len(types) == 1 and isinstance(first_arg, (Parameters, ParamSpecType, AnyType))
		):
		single_any = len(types) == 1 and isinstance(first_arg, AnyType)
		if not (single_any or any(isinstance(t, (Parameters, ParamSpecType)) for t in types)):
		types = [Parameters(types, [ARG_POS] * len(types), [None] * len(types))]

		return types
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1836,6 +1836,15 @@ c: C[int, [int, str], str] # E: Nested parameter specifications are not allowed
		reveal_type(c) # N: Revealed type is "__main__.C[Any]"
		[builtins fixtures/paramspec.pyi]

		[case testParamSpecInheritNoCrashOnNested]
		from typing import Generic
		from typing_extensions import ParamSpec

		P = ParamSpec("P")
		class C(Generic[P]): ...
		class D(C[int, [int, str], str]): ... # E: Nested parameter specifications are not allowed
		[builtins fixtures/paramspec.pyi]

		[case testParamSpecConcatenateSelfType]
		from typing import Callable
		from typing_extensions import ParamSpec, Concatenate
Expand Down