Fix overloading on Type[...] (#4037)

Fixes #4027

Currently overloads on `Type[...]` don't accept class objects whose `__init__` is itself overloaded. I fix this by simply allowing `FunctionLike` with `.is_type_obj()` returning `True` instead of only `Callable`.

Author: ilevkivskyi

mypy/checkexpr.py

@@ -2817,10 +2817,10 @@ def overload_arg_similarity(actual: Type, formal: Type) -> int:
             # Since Type[T] is covariant, check if actual = Type[A] is
             # a subtype of formal = Type[F].
             return overload_arg_similarity(actual.item, formal.item)
-        elif isinstance(actual, CallableType) and actual.is_type_obj():
+        elif isinstance(actual, FunctionLike) and actual.is_type_obj():
             # Check if the actual is a constructor of some sort.
             # Note that this is this unsound, since we don't check the __init__ signature.
-            return overload_arg_similarity(actual.ret_type, formal.item)
+            return overload_arg_similarity(actual.items()[0].ret_type, formal.item)
         else:
             return 0
     if isinstance(actual, TypedDictType):

test-data/unit/check-overloading.test

@@ -1272,3 +1272,28 @@ a: Any
 # The return type is not ambiguous so Any arguments cause no ambiguity.
 reveal_type(f(a, 1, 1)) # E: Revealed type is 'builtins.str'
 reveal_type(f(1, *a))  # E: Revealed type is 'builtins.str'
+
+[case testOverloadOnOverloadWithType]
+from typing import Any, Type, TypeVar, overload
+from mod import MyInt
+T = TypeVar('T')
+
+@overload
+def make(cls: Type[T]) -> T: pass
+@overload
+def make() -> Any: pass
+
+def make(*args):
+    pass
+
+c = make(MyInt)
+reveal_type(c) # E: Revealed type is 'mod.MyInt*'
+
+[file mod.pyi]
+from typing import overload
+class MyInt:
+    @overload
+    def __init__(self, x: str) -> None: pass
+    @overload
+    def __init__(self, x: str, y: int) -> None: pass
+[out]