Fix codecs.register_error callback type

The callback receives one of the three concrete Unicode codec error types. Model that union so contextual typing exposes their shared attributes.

Author: stroxler

stdlib/@tests/test_cases/check_codecs.py

@@ -11,3 +11,5 @@
 
 assert_type(codecs.decode("ab", "hex"), bytes)
 assert_type(codecs.decode(b"ab", "hex"), bytes)
+
+codecs.register_error("test", lambda error: (assert_type(error.object, str | bytes), assert_type(error.end, int)))

stdlib/_codecs.pyi

@@ -13,7 +13,8 @@ class _EncodingMap:
 
 _DecodeCharMap: TypeAlias = SupportsGetItem[int, str | int | None]
 _EncodeCharMap: TypeAlias = SupportsGetItem[int, bytes | int | None] | _EncodingMap
-_Handler: TypeAlias = Callable[[UnicodeError], tuple[str | bytes, int]]
+_CodecError: TypeAlias = UnicodeEncodeError | UnicodeDecodeError | UnicodeTranslateError
+_Handler: TypeAlias = Callable[[_CodecError], tuple[str | bytes, int]]
 _SearchFunction: TypeAlias = Callable[[str], codecs.CodecInfo | None]
 
 def register(search_function: _SearchFunction, /) -> None: ...