fix(checker): avoid crash for constrained unpacked args

mypy/types_utils.py

@@ -154,6 +154,10 @@ def is_self_type_like(typ: Type, *, is_classmethod: bool) -> bool:
 def store_argument_type(
     defn: FuncItem, i: int, typ: CallableType, named_type: Callable[[str, list[Type]], Instance]
 ) -> None:
+    # Expanding an unpacked tuple can add synthetic positional arguments to
+    # the callable type without adding corresponding AST arguments.
+    if i >= len(defn.arguments):
+        return
     arg_type = typ.arg_types[i]
     if typ.arg_kinds[i] == ARG_STAR:
         if isinstance(arg_type, ParamSpecType):

test-data/unit/check-generics.test

@@ -3737,3 +3737,14 @@ def test(tp: type[T]) -> T: ...
 
 class C(Generic[T]): ...
 reveal_type(test(C))  # N: Revealed type is "__main__.C[Any]"
+
+[case testConstrainedTypeVarWithUnpackedArgs]
+from typing import Callable, Tuple, TypeVar
+from typing_extensions import Unpack
+
+T = TypeVar("T", str, bytes)
+
+def generic_fun(a: Callable[..., T], *args: Unpack[Tuple[int, float]]) -> None: ...
+
+generic_fun(lambda: "value", 1, 2.0)
+[builtins fixtures/tuple.pyi]