Fix plugin invocation for __call__ methods

mypy/checkexpr.py

@@ -707,8 +707,12 @@ def check_call(self,
                                                   False, False, False, self.msg,
                                                   original_type=callee, chk=self.chk,
                                                   in_literal_context=self.is_literal_context())
+            callable_name = callee.type.fullname() + ".__call__"
+            # Apply method signature hook, if one exists
+            call_function = self.transform_callee_type(
+                callable_name, call_function, args, arg_kinds, context, arg_names, callee)
             return self.check_call(call_function, args, arg_kinds, context, arg_names,
-                                   callable_node, arg_messages)
+                                   callable_node, arg_messages, callable_name, callee)
         elif isinstance(callee, TypeVarType):
             return self.check_call(callee.upper_bound, args, arg_kinds, context, arg_names,
                                    callable_node, arg_messages)

test-data/unit/check-custom-plugin.test

@@ -394,11 +394,13 @@ class Foo:
     def __setitem__(self, index: str, value: str) -> None: ...
     def __iter__(self) -> Iterator[str]: ...
     def __next__(self) -> str: ...
+    def __call__(self, *args: str) -> str: ...
     def m(self, arg: str) -> str: ...
 
 foo = Foo()
 reveal_type(foo.m(2)) # E: Revealed type is 'builtins.int'
 reveal_type(foo[3]) # E: Revealed type is 'builtins.int'
+reveal_type(foo(4, 5, 6)) # E: Revealed type is 'builtins.int'
 foo[4] = 5
 for x in foo:
     reveal_type(x) # E: Revealed type is 'builtins.int*'
@@ -536,3 +538,18 @@ func(1, 2, [3, 4], *[5, 6, 7], **{'a': 1})  # E: [[0, 0, 0, 2], [4]]
 [file mypy.ini]
 [[mypy]
 plugins=<ROOT>/test-data/unit/plugins/arg_kinds.py
+
+[case testHookCallableInstance]
+# flags: --config-file tmp/mypy.ini
+from typing import Generic, TypeVar
+T = TypeVar("T")
+class Class(Generic[T]):
+    def __init__(self, one: T): ...
+    def __call__(self, two: T) -> int: ...
+reveal_type(Class("hi")("there"))  # E: Revealed type is 'builtins.str*'
+instance = Class(3.14)
+reveal_type(instance(2))  # E: Revealed type is 'builtins.float*'
+
+[file mypy.ini]
+[[mypy]
+plugins=<ROOT>/test-data/unit/plugins/callable_instance.py

test-data/unit/plugins/callable_instance.py

@@ -0,0 +1,23 @@
+from mypy.plugin import MethodContext, Plugin
+from mypy.types import Instance, Type
+
+class CallableInstancePlugin(Plugin):
+    def get_function_hook(self, fullname):
+        assert not fullname.endswith(' of Foo')
+
+    def get_method_hook(self, fullname):
+        # Ensure that all names are fully qualified
+        assert not fullname.endswith(' of Foo')
+
+        if fullname == '__main__.Class.__call__':
+            return my_hook
+
+        return None
+
+def my_hook(ctx: MethodContext) -> Type:
+    if isinstance(ctx.type, Instance) and len(ctx.type.args) == 1:
+        return ctx.type.args[0]
+    return ctx.default_return_type
+
+def plugin(version):
+    return CallableInstancePlugin