Bail out if Parameters are generic themselves

Author: sterliakov

mypy/expandtype.py

@@ -304,6 +304,9 @@ def _possible_callable_varargs(
         of other arguments that can be passed positionally.
         """
         required_posargs = required_prefix
+        if repl.variables:
+            # We will tear the callable apart, do not leak type variables
+            return tuple_type
         optional_posargs: list[Type] = []
         for kind, name, type in zip(repl.arg_kinds, repl.arg_names, repl.arg_types):
             if kind == ArgKind.ARG_POS and name is None:
@@ -336,6 +339,9 @@ def _possible_callable_kwargs(cls, repl: Parameters, dict_type: Instance) -> Pro
         `**kwargs` (until PEP 728 `extra_items` is supported). TypedDict entries will
         be required iff the corresponding argument is kw-only and has no default.
         """
+        if repl.variables:
+            # We will tear the callable apart, do not leak type variables
+            return dict_type
         kwargs = {}
         required_names = set()
         extra_items: Type = UninhabitedType()

test-data/unit/check-parameter-specification.test

@@ -2680,6 +2680,33 @@ reveal_type(SneakyPrefix(f10, 1, '', '').args)  # N: Revealed type is "Union[tup
 reveal_type(Sneaky(f11).args)  # N: Revealed type is "Union[tuple[()], tuple[builtins.int]]"
 [builtins fixtures/paramspec.pyi]
 
+[case testRevealBoundParamSpecGeneric]
+from typing import Callable, Generic, ParamSpec, TypeVar
+from typing_extensions import TypeVarTuple, Unpack
+
+T = TypeVar("T")
+P = ParamSpec("P")
+Ts = TypeVarTuple("Ts")
+
+class SplitSneaky(Generic[P]):
+    def __init__(self, target: Callable[P, None]) -> None:
+        ...
+
+    def run(self, *args: P.args, **kwargs: P.kwargs) -> None:
+        self.args = args
+        self.kwargs = kwargs
+
+def f1(x: T) -> None: ...
+def f2(*xs: Unpack[Ts]) -> None: ...
+def f3(fn: Callable[P, None]) -> None: ...
+
+reveal_type(SplitSneaky(f1).args)  # N: Revealed type is "builtins.tuple[builtins.object, ...]"
+reveal_type(SplitSneaky(f1).kwargs)  # N: Revealed type is "builtins.dict[builtins.str, builtins.object]"
+reveal_type(SplitSneaky(f2).args)  # N: Revealed type is "builtins.tuple[builtins.object, ...]"
+reveal_type(SplitSneaky(f2).kwargs)  # N: Revealed type is "builtins.dict[builtins.str, builtins.object]"
+reveal_type(SplitSneaky(f3).args)  # N: Revealed type is "builtins.tuple[builtins.object, ...]"
+reveal_type(SplitSneaky(f3).kwargs)  # N: Revealed type is "builtins.dict[builtins.str, builtins.object]"
+[builtins fixtures/paramspec.pyi]
 
 [case testRevealBoundParamSpecKwargs]
 from typing import Callable, Generic, ParamSpec