move DataclassInstance to dataclasses.pyi

test-data/unit/check-dataclass-transform.test

@@ -853,7 +853,7 @@ class Person:
     name: str
 
 p = Person('John')
-y = replace(p, name='Bob')  # E: Argument 1 to "replace" has incompatible type "Person"; expected a dataclass
+y = replace(p, name='Bob')
 
 [typing fixtures/typing-full.pyi]
 [builtins fixtures/dataclasses.pyi]

test-data/unit/lib-stub/_typeshed.pyi

@@ -1,12 +1,8 @@
-from dataclasses import Field
-from typing import Any, ClassVar, Protocol, TypeVar, Iterable
+from typing import Protocol, TypeVar, Iterable
 
 _KT = TypeVar("_KT")
 _VT_co = TypeVar("_VT_co", covariant=True)
 
 class SupportsKeysAndGetItem(Protocol[_KT, _VT_co]):
     def keys(self) -> Iterable[_KT]: pass
     def __getitem__(self, __key: _KT) -> _VT_co: pass
-
-class DataclassInstance(Protocol):
-    __dataclass_fields__: ClassVar[dict[str, Field[Any]]]

test-data/unit/lib-stub/dataclasses.pyi

@@ -1,7 +1,12 @@
-from _typeshed import DataclassInstance
-from typing import Any, Callable, Generic, Literal, Mapping, Optional, TypeVar, overload, Type
+from typing import Any, Callable, Generic, Literal, Mapping, Optional, TypeVar, overload, Type, \
+    Protocol, ClassVar
 from typing_extensions import TypeGuard
 
+# DataclassInstance is in _typeshed.pyi normally, but alas we can't do the same for lib-stub
+# due to test-data/unit/lib-stub/builtins.pyi not having 'tuple'.
+class DataclassInstance(Protocol):
+    __dataclass_fields__: ClassVar[dict[str, Field[Any]]]
+
 _T = TypeVar('_T')
 _DataclassT = TypeVar("_DataclassT", bound=DataclassInstance)