hacks

Author: hauntsaninja

mypy/checkexpr.py

@@ -3182,11 +3182,11 @@ def analyze_ordinary_member_access(self, e: MemberExpr, is_lvalue: bool) -> Type
             member_type = analyze_member_access(
                 e.name,
                 original_type,
-                e,
-                is_lvalue,
-                False,
-                False,
-                self.msg,
+                context=e,
+                is_lvalue=is_lvalue,
+                is_super=False,
+                is_operator=False,
+                msg=self.msg,
                 original_type=original_type,
                 chk=self.chk,
                 in_literal_context=self.is_literal_context(),

mypy/checkmember.py

@@ -371,7 +371,27 @@ def validate_super_call(node: FuncBase, mx: MemberContext) -> None:
 def analyze_type_callable_member_access(name: str, typ: FunctionLike, mx: MemberContext) -> Type:
     # Class attribute.
     # TODO super?
-    ret_type = typ.items[0].ret_type
+    item = typ.items[0]
+    ret_type = item.ret_type
+
+    # The following is a hack. mypy often represents types as CallableType, where the signature of
+    # CallableType is determined by __new__ or __init__ of the type (this logic is in
+    # type_object_type). Then if we ever need the TypeInfo or an instance of the type, we fish
+    # around for the return type in CallableType.type_object. Unfortunately, this is incorrect if
+    # __new__ returns an unrelated type, but we can kind of salvage things by fishing around in
+    # CallableType.bound_args
+    self_type: Type = typ
+    if len(item.bound_args) == 1 and item.bound_args[0]:
+        bound_arg = get_proper_type(item.bound_args[0])
+        proper_ret_type = get_proper_type(ret_type)
+        if isinstance(bound_arg, Instance) and isinstance(proper_ret_type, Instance):
+            # Unfortunately, generic arguments have already been determined for us. We need these,
+            # see e.g. testGenericClassMethodUnboundOnClass. So just copy them over to our type.
+            # This does the wrong thing with custom __new__, see testNewReturnType15, but is
+            # a lesser evil.
+            ret_type = bound_arg.copy_modified(args=proper_ret_type.args)
+            self_type = TypeType(ret_type)
+
     assert isinstance(ret_type, ProperType)
     if isinstance(ret_type, TupleType):
         ret_type = tuple_fallback(ret_type)
@@ -394,7 +414,11 @@ def analyze_type_callable_member_access(name: str, typ: FunctionLike, mx: Member
             # See https://github.com/python/mypy/pull/1787 for more info.
             # TODO: do not rely on same type variables being present in all constructor overloads.
             result = analyze_class_attribute_access(
-                ret_type, name, mx, original_vars=typ.items[0].variables, mcs_fallback=typ.fallback
+                ret_type,
+                name,
+                mx.copy_modified(self_type=self_type),
+                original_vars=typ.items[0].variables,
+                mcs_fallback=typ.fallback,
             )
             if result:
                 return result

mypy/typeops.py

@@ -202,10 +202,9 @@ def class_callable(
             # this case (although we should probably change it at some point)
             # See testValueTypeWithNewInParentClass
             # Also see testSelfTypeInGenericClassUsedFromAnotherGenericClass1
-            if (
-                not is_subtype(default_ret_type, explicit_type, ignore_type_params=True)
-                or is_subtype(explicit_type, default_ret_type, ignore_type_params=True)
-            ):
+            if not is_subtype(
+                default_ret_type, explicit_type, ignore_type_params=True
+            ) or is_subtype(explicit_type, default_ret_type, ignore_type_params=True):
                 ret_type = explicit_type
         elif (
             # We have to skip protocols, because it can be a subtype of a return type

mypy/types.py

@@ -1466,7 +1466,7 @@ def deserialize(cls, data: JsonDict | str) -> Instance:
     def copy_modified(
         self,
         *,
-        args: Bogus[list[Type]] = _dummy,
+        args: Bogus[Sequence[Type]] = _dummy,
         last_known_value: Bogus[LiteralType | None] = _dummy,
     ) -> Instance:
         new = Instance(

test-data/unit/check-classes.test

@@ -7007,6 +7007,41 @@ reveal_type(A())  # E: Cannot instantiate protocol class "Foo" \
 reveal_type(A().foo())  # E: Cannot instantiate protocol class "Foo" \
                         # N: Revealed type is "builtins.str"
 
+[case testNewReturnType14]
+from __future__ import annotations
+
+class A:
+    def __new__(cls) -> int: raise  # E: Incompatible return type for "__new__" (returns "int", but must return a subtype of "A")
+
+class B(A):
+    @classmethod
+    def foo(cls) -> int: raise
+
+reveal_type(B.foo())  # N: Revealed type is "builtins.int"
+[builtins fixtures/classmethod.pyi]
+
+[case testNewReturnType15]
+from typing import Generic, Type, TypeVar
+
+T = TypeVar("T")
+
+class A(Generic[T]):
+    def __new__(cls) -> B[int]: ...
+    @classmethod
+    def foo(cls: Type[T]) -> T: ...
+
+class B(A[T]): ...
+
+# These are incorrect, should be Any and str
+# See https://github.com/python/mypy/pull/16020
+reveal_type(B.foo())  # N: Revealed type is "builtins.int"
+reveal_type(B[str].foo())  # N: Revealed type is "builtins.int"
+
+class C(A[str]): ...
+
+reveal_type(C.foo())  # N: Revealed type is "builtins.str"
+[builtins fixtures/classmethod.pyi]
+
 [case testMetaclassPlaceholderNode]
 from sympy.assumptions import ManagedProperties
 from sympy.ops import AssocOp