[_cffi_backend] Improve CField, CType, _CDataBase, buffer

stubs/cffi/_cffi_backend.pyi

@@ -1,6 +1,6 @@
 import sys
 import types
-from _typeshed import Incomplete, ReadableBuffer, WriteableBuffer
+from _typeshed import ReadableBuffer, WriteableBuffer
 from collections.abc import Callable, Hashable
 from typing import Any, ClassVar, Literal, Protocol, SupportsIndex, TypeVar, final, overload, type_check_only
 from typing_extensions import Self, TypeAlias, disjoint_base
@@ -27,11 +27,11 @@ if sys.platform != "win32":
 
 @final
 class CField:
-    bitshift: Incomplete
-    bitsize: Incomplete
-    flags: Incomplete
-    offset: Incomplete
-    type: Incomplete
+    bitshift: int
+    bitsize: int
+    flags: int
+    offset: int
+    type: CType
 
 @final
 class CLibrary:
@@ -42,18 +42,21 @@ class CLibrary:
 
 @final
 class CType:
-    abi: Incomplete
-    args: Incomplete
-    cname: Incomplete
-    elements: Incomplete
-    ellipsis: Incomplete
-    fields: Incomplete
-    item: Incomplete
-    kind: Incomplete
-    length: Incomplete
-    relements: Incomplete
-    result: Incomplete
-    def __dir__(self): ...
+    cname: str
+    kind: Literal["enum", "primitive", "pointer", "array", "void", "struct", "union", "function"]
+
+    abi: int
+    args: tuple[CType, ...]
+    ellipsis: bool
+    result: CType
+
+    item: CType
+    length: int | None
+
+    fields: list[tuple[str, CField]] | None
+
+    relements: dict[str, int]
+    elements: dict[int, str]
 
 @final
 class Lib:
@@ -62,48 +65,46 @@ class Lib:
 @final
 class _CDataBase:
     __name__: ClassVar[str]
-    def __add__(self, other, /): ...
-    def __bool__(self) -> bool: ...
-    def __call__(self, *args, **kwargs): ...
-    def __complex__(self) -> complex: ...
-    def __delitem__(self, other, /) -> None: ...
     def __dir__(self): ...
-    def __enter__(self): ...
-    def __eq__(self, other, /): ...
+    def __enter__(self) -> Self: ...
     def __exit__(
         self, type: type[BaseException] | None, value: BaseException | None, traceback: types.TracebackType | None, /
     ): ...
+    def __add__(self, other, /): ...
+    def __sub__(self, other, /): ...
+    def __radd__(self, other, /): ...
+    def __rsub__(self, other, /): ...
+    def __call__(self, *args): ...
+    def __hash__(self) -> int: ...
+    def __bool__(self) -> bool: ...
+    def __int__(self) -> int: ...
     def __float__(self) -> float: ...
+    def __complex__(self) -> complex: ...
+    def __eq__(self, other, /): ...
+    def __ne__(self, other, /): ...
     def __ge__(self, other, /): ...
-    def __getitem__(self, index: SupportsIndex | slice, /): ...
     def __gt__(self, other, /): ...
-    def __hash__(self) -> int: ...
-    def __int__(self) -> int: ...
-    def __iter__(self): ...
     def __le__(self, other, /): ...
-    def __len__(self) -> int: ...
     def __lt__(self, other, /): ...
-    def __ne__(self, other, /): ...
-    def __radd__(self, other, /): ...
-    def __rsub__(self, other, /): ...
+    def __iter__(self): ...
+    def __len__(self) -> int: ...
+    def __getitem__(self, index: SupportsIndex | slice, /): ...
     def __setitem__(self, index: SupportsIndex | slice, object, /) -> None: ...
-    def __sub__(self, other, /): ...
 
 @final
 class buffer:
     __hash__: ClassVar[None]  # type: ignore[assignment]
-    def __new__(cls, *args, **kwargs) -> Self: ...
+    def __new__(cls, cdata: _CDataBase, size: int = -1) -> Self: ...
     def __buffer__(self, flags: int, /) -> memoryview: ...
-    def __delitem__(self, other, /) -> None: ...
-    def __eq__(self, other, /): ...
-    def __ge__(self, other, /): ...
-    def __getitem__(self, index, /): ...
-    def __gt__(self, other, /): ...
-    def __le__(self, other, /): ...
+    def __eq__(self, other: ReadableBuffer, /) -> bool: ...  # type: ignore[override]
+    def __ne__(self, other: ReadableBuffer, /) -> bool: ...  # type: ignore[override]
+    def __ge__(self, other: ReadableBuffer, /) -> bool: ...
+    def __gt__(self, other: ReadableBuffer, /) -> bool: ...
+    def __le__(self, other: ReadableBuffer, /) -> bool: ...
+    def __lt__(self, other: ReadableBuffer, /) -> bool: ...
     def __len__(self) -> int: ...
-    def __lt__(self, other, /): ...
-    def __ne__(self, other, /): ...
-    def __setitem__(self, index, object, /) -> None: ...
+    def __getitem__(self, index: SupportsIndex | slice, /) -> bytes: ...
+    def __setitem__(self, index: SupportsIndex | slice, value: bytes, /) -> None: ...
 
 # These aliases are to work around pyright complaints.
 # Pyright doesn't like it when a class object is defined as an alias