Fix crash with type alias to `Callable[[Unpack[Tuple[Any, ...]]], Any…

…]` (#16541)

Fixes #16533

mypy/expandtype.py

@@ -307,18 +307,24 @@ def interpolate_args_for_unpack(self, t: CallableType, var_arg: UnpackType) -> l
         suffix = self.expand_types(t.arg_types[star_index + 1 :])
 
         var_arg_type = get_proper_type(var_arg.type)
-        # We have something like Unpack[Tuple[Unpack[Ts], X1, X2]]
-        if isinstance(var_arg_type, TupleType):
-            expanded_tuple = var_arg_type.accept(self)
-            assert isinstance(expanded_tuple, ProperType) and isinstance(expanded_tuple, TupleType)
-            expanded_items = expanded_tuple.items
-            fallback = var_arg_type.partial_fallback
+        if isinstance(var_arg_type, Instance):
+            # we have something like Unpack[Tuple[Any, ...]]
+            new_unpack = var_arg
         else:
-            # We have plain Unpack[Ts]
-            assert isinstance(var_arg_type, TypeVarTupleType)
-            fallback = var_arg_type.tuple_fallback
-            expanded_items = self.expand_unpack(var_arg)
-        new_unpack = UnpackType(TupleType(expanded_items, fallback))
+            if isinstance(var_arg_type, TupleType):
+                # We have something like Unpack[Tuple[Unpack[Ts], X1, X2]]
+                expanded_tuple = var_arg_type.accept(self)
+                assert isinstance(expanded_tuple, ProperType) and isinstance(
+                    expanded_tuple, TupleType
+                )
+                expanded_items = expanded_tuple.items
+                fallback = var_arg_type.partial_fallback
+            else:
+                # We have plain Unpack[Ts]
+                assert isinstance(var_arg_type, TypeVarTupleType), type(var_arg_type)
+                fallback = var_arg_type.tuple_fallback
+                expanded_items = self.expand_unpack(var_arg)
+            new_unpack = UnpackType(TupleType(expanded_items, fallback))
         return prefix + [new_unpack] + suffix
 
     def visit_callable_type(self, t: CallableType) -> CallableType:

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

@@ -2235,3 +2235,45 @@ z: Tuple[int, Unpack[Tuple[int, ...]]] = (1,)
 w: Tuple[int, Unpack[Tuple[int, ...]]] = (1, *[2, 3, 4])
 t: Tuple[int, Unpack[Tuple[int, ...]]] = (1, *(2, 3, 4))
 [builtins fixtures/tuple.pyi]
+
+[case testAliasToCallableWithUnpack]
+from typing import Any, Callable, Tuple, Unpack
+
+_CallableValue = Callable[[Unpack[Tuple[Any, ...]]], Any]
+def higher_order(f: _CallableValue) -> None: ...
+
+def good1(*args: int) -> None: ...
+def good2(*args: str) -> int: ...
+
+def bad1(a: str, b: int, /) -> None: ...
+def bad2(c: bytes, *args: int) -> str: ...
+def bad3(*, d: str) -> int: ...
+def bad4(**kwargs: None) -> None: ...
+
+higher_order(good1)
+higher_order(good2)
+
+higher_order(bad1)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[str, int], None]"; expected "Callable[[VarArg(Any)], Any]"
+higher_order(bad2)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[bytes, VarArg(int)], str]"; expected "Callable[[VarArg(Any)], Any]"
+higher_order(bad3)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[NamedArg(str, 'd')], int]"; expected "Callable[[VarArg(Any)], Any]"
+higher_order(bad4)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[KwArg(None)], None]"; expected "Callable[[VarArg(Any)], Any]"
+[builtins fixtures/tuple.pyi]
+
+[case testAliasToCallableWithUnpack2]
+from typing import Any, Callable, Tuple, Unpack
+
+_CallableValue = Callable[[int, str, Unpack[Tuple[Any, ...]], int], Any]
+def higher_order(f: _CallableValue) -> None: ...
+
+def good(a: int, b: str, *args: Unpack[Tuple[Unpack[Tuple[Any, ...]], int]]) -> int: ...
+def bad1(a: str, b: int, /) -> None: ...
+def bad2(c: bytes, *args: int) -> str: ...
+def bad3(*, d: str) -> int: ...
+def bad4(**kwargs: None) -> None: ...
+
+higher_order(good)
+higher_order(bad1)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[str, int], None]"; expected "Callable[[int, str, VarArg(Unpack[Tuple[Unpack[Tuple[Any, ...]], int]])], Any]"
+higher_order(bad2)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[bytes, VarArg(int)], str]"; expected "Callable[[int, str, VarArg(Unpack[Tuple[Unpack[Tuple[Any, ...]], int]])], Any]"
+higher_order(bad3)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[NamedArg(str, 'd')], int]"; expected "Callable[[int, str, VarArg(Unpack[Tuple[Unpack[Tuple[Any, ...]], int]])], Any]"
+higher_order(bad4)  # E: Argument 1 to "higher_order" has incompatible type "Callable[[KwArg(None)], None]"; expected "Callable[[int, str, VarArg(Unpack[Tuple[Unpack[Tuple[Any, ...]], int]])], Any]"
+[builtins fixtures/tuple.pyi]