Use Self for __new__ implementations (#259)

Author: bigfootjon

src/graphql/pyutils/undefined.py

@@ -3,16 +3,23 @@
 from __future__ import annotations
 
 import warnings
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    try:
+        from typing import Self
+    except ImportError:  # Python < 3.11
+        from typing_extensions import Self
 
 __all__ = ["Undefined", "UndefinedType"]
 
 
 class UndefinedType:
     """Auxiliary class for creating the Undefined singleton."""
 
-    _instance: UndefinedType | None = None
+    _instance: Self | None = None
 
-    def __new__(cls) -> UndefinedType:
+    def __new__(cls) -> Self:
         """Create the Undefined singleton."""
         if cls._instance is None:
             cls._instance = super().__new__(cls)

src/graphql/type/definition.py

@@ -59,6 +59,11 @@
 if TYPE_CHECKING:
     from .schema import GraphQLSchema
 
+    try:
+        from typing import Self
+    except ImportError:  # Python < 3.11
+        from typing_extensions import Self
+
 
 __all__ = [
     "GraphQLAbstractType",
@@ -232,7 +237,7 @@ class GraphQLNamedType(GraphQLType):
 
     reserved_types: Mapping[str, GraphQLNamedType] = {}
 
-    def __new__(cls, name: str, *_args: Any, **_kwargs: Any) -> GraphQLNamedType:
+    def __new__(cls, name: str, *_args: Any, **_kwargs: Any) -> Self:
         """Create a GraphQL named type."""
         if name in cls.reserved_types:
             msg = f"Redefinition of reserved type {name!r}"