Fix subtyping between Instance and Overloaded (#18102)

Fixes #18101

mypy/subtypes.py

@@ -625,8 +625,8 @@ def visit_instance(self, left: Instance) -> bool:
                         return is_named_instance(item, "builtins.object")
         if isinstance(right, LiteralType) and left.last_known_value is not None:
             return self._is_subtype(left.last_known_value, right)
-        if isinstance(right, CallableType):
-            # Special case: Instance can be a subtype of Callable.
+        if isinstance(right, FunctionLike):
+            # Special case: Instance can be a subtype of Callable / Overloaded.
             call = find_member("__call__", left, left, is_operator=True)
             if call:
                 return self._is_subtype(call, right)

test-data/unit/check-protocols.test

@@ -4215,3 +4215,24 @@ def g4(a: Input[bytes], b: Output[str]) -> None:
     f(a, b)  # E: Cannot infer type argument 1 of "f"
 
 [builtins fixtures/tuple.pyi]
+
+[case testOverloadProtocolSubtyping]
+from typing import Protocol, Self, overload
+
+class NumpyFloat:
+    __add__: "FloatOP"
+
+class FloatOP(Protocol):
+    @overload
+    def __call__(self, other: float) -> NumpyFloat: ...
+    @overload
+    def __call__(self, other: NumpyFloat) -> NumpyFloat: ...
+
+class SupportsAdd(Protocol):
+    @overload
+    def __add__(self, other: float) -> Self: ...
+    @overload
+    def __add__(self, other: NumpyFloat) -> Self: ...
+
+x: SupportsAdd = NumpyFloat()
+[builtins fixtures/tuple.pyi]