Make any callable compatible with (*args: Any, **kwargs: Any)

Resolves python#5876

Author: hauntsaninja

mypy/subtypes.py

@@ -18,7 +18,7 @@
 # import mypy.solve
 from mypy.nodes import (
     FuncBase, Var, Decorator, OverloadedFuncDef, TypeInfo, CONTRAVARIANT, COVARIANT,
-
+    ARG_STAR, ARG_STAR2,
 )
 from mypy.maptype import map_instance_to_supertype
 from mypy.expandtype import expand_type_by_instance
@@ -893,6 +893,14 @@ def g(x: int) -> int: ...
     right_star = right.var_arg()
     right_star2 = right.kw_arg()
 
+    # Treat "def _(*a: Any, **kw: Any) -> X" similarly to "Callable[..., X]"
+    if (
+        right.arg_kinds == [ARG_STAR, ARG_STAR2]
+        and right_star and isinstance(right_star.typ, AnyType)
+        and right_star2 and isinstance(right_star2.typ, AnyType)
+    ):
+        return True
+
     # Match up corresponding arguments and check them for compatibility. In
     # every pair (argL, argR) of corresponding arguments from L and R, argL must
     # be "more general" than argR if L is to be a subtype of R.