Handle type same as typing.Type in classmethod 1st arg (#15297)

Author: erikkemperman

mypy/semanal.py

@@ -1008,7 +1008,21 @@ def is_expected_self_type(self, typ: Type, is_classmethod: bool) -> bool:
                 return self.is_expected_self_type(typ.item, is_classmethod=False)
             if isinstance(typ, UnboundType):
                 sym = self.lookup_qualified(typ.name, typ, suppress_errors=True)
-                if sym is not None and sym.fullname == "typing.Type" and typ.args:
+                if (
+                    sym is not None
+                    and (
+                        sym.fullname == "typing.Type"
+                        or (
+                            sym.fullname == "builtins.type"
+                            and (
+                                self.is_stub_file
+                                or self.is_future_flag_set("annotations")
+                                or self.options.python_version >= (3, 9)
+                            )
+                        )
+                    )
+                    and typ.args
+                ):
                     return self.is_expected_self_type(typ.args[0], is_classmethod=False)
             return False
         if isinstance(typ, TypeVarType):

test-data/unit/check-selftype.test

@@ -1665,6 +1665,23 @@ class C:
         return cls()
 [builtins fixtures/classmethod.pyi]
 
+[case testTypingSelfRedundantAllowed_pep585]
+# flags: --python-version 3.9
+from typing import Self
+
+class C:
+    def f(self: Self) -> Self:
+        d: Defer
+        class Defer: ...
+        return self
+
+    @classmethod
+    def g(cls: type[Self]) -> Self:
+        d: DeferAgain
+        class DeferAgain: ...
+        return cls()
+[builtins fixtures/classmethod.pyi]
+
 [case testTypingSelfRedundantWarning]
 # mypy: enable-error-code="redundant-self"
 
@@ -1683,6 +1700,25 @@ class C:
         return cls()
 [builtins fixtures/classmethod.pyi]
 
+[case testTypingSelfRedundantWarning_pep585]
+# flags: --python-version 3.9
+# mypy: enable-error-code="redundant-self"
+
+from typing import Self
+
+class C:
+    def copy(self: Self) -> Self:  # E: Redundant "Self" annotation for the first method argument
+        d: Defer
+        class Defer: ...
+        return self
+
+    @classmethod
+    def g(cls: type[Self]) -> Self:  # E: Redundant "Self" annotation for the first method argument
+        d: DeferAgain
+        class DeferAgain: ...
+        return cls()
+[builtins fixtures/classmethod.pyi]
+
 [case testTypingSelfAssertType]
 from typing import Self, assert_type