Reduce code duplication in the email module

stdlib/email/__init__.pyi

@@ -1,6 +1,11 @@
 from email.message import Message
 from email.policy import Policy
-from typing import IO, Callable
+from typing import IO, Callable, TypeVar, Union
+
+# Definitions imported by multiple submodules in typeshed
+_MessageT = TypeVar("_MessageT", bound=Message)  # noqa: Y018
+_ParamType = Union[str, tuple[str | None, str | None, str]]
+_ParamsType = Union[str, None, tuple[str, str | None, str]]
 
 def message_from_string(s: str, _class: Callable[[], Message] = ..., *, policy: Policy = ...) -> Message: ...
 def message_from_bytes(s: bytes, _class: Callable[[], Message] = ..., *, policy: Policy = ...) -> Message: ...

stdlib/email/feedparser.pyi

@@ -1,23 +1,22 @@
+from email import _MessageT
 from email.message import Message
 from email.policy import Policy
-from typing import Callable, Generic, TypeVar, overload
+from typing import Callable, Generic, overload
 
 __all__ = ["FeedParser", "BytesFeedParser"]
 
-_M = TypeVar("_M", bound=Message)
-
-class FeedParser(Generic[_M]):
+class FeedParser(Generic[_MessageT]):
     @overload
     def __init__(self: FeedParser[Message], _factory: None = ..., *, policy: Policy = ...) -> None: ...
     @overload
-    def __init__(self, _factory: Callable[[], _M], *, policy: Policy = ...) -> None: ...
+    def __init__(self, _factory: Callable[[], _MessageT], *, policy: Policy = ...) -> None: ...
     def feed(self, data: str) -> None: ...
-    def close(self) -> _M: ...
+    def close(self) -> _MessageT: ...
 
-class BytesFeedParser(Generic[_M]):
+class BytesFeedParser(Generic[_MessageT]):
     @overload
     def __init__(self: BytesFeedParser[Message], _factory: None = ..., *, policy: Policy = ...) -> None: ...
     @overload
-    def __init__(self, _factory: Callable[[], _M], *, policy: Policy = ...) -> None: ...
+    def __init__(self, _factory: Callable[[], _MessageT], *, policy: Policy = ...) -> None: ...
     def feed(self, data: bytes) -> None: ...
-    def close(self) -> _M: ...
+    def close(self) -> _MessageT: ...

stdlib/email/message.pyi

@@ -1,17 +1,16 @@
+from email import _ParamsType, _ParamType
 from email.charset import Charset
 from email.contentmanager import ContentManager
 from email.errors import MessageDefect
 from email.policy import Policy
-from typing import Any, Generator, Iterator, Sequence, TypeVar, Union
+from typing import Any, Generator, Iterator, Sequence, TypeVar
 
 __all__ = ["Message", "EmailMessage"]
 
 _T = TypeVar("_T")
 
 _PayloadType = list[Message] | str | bytes
 _CharsetType = Charset | str | None
-_ParamsType = Union[str, None, tuple[str, str | None, str]]
-_ParamType = Union[str, tuple[str | None, str | None, str]]
 _HeaderType = Any
 
 class Message:

stdlib/email/mime/application.pyi

@@ -1,11 +1,10 @@
+from collections.abc import Callable
+from email import _ParamsType
 from email.mime.nonmultipart import MIMENonMultipart
 from email.policy import Policy
-from typing import Callable, Union
 
 __all__ = ["MIMEApplication"]
 
-_ParamsType = Union[str, None, tuple[str, str | None, str]]
-
 class MIMEApplication(MIMENonMultipart):
     def __init__(
         self,

stdlib/email/mime/audio.pyi

@@ -1,11 +1,10 @@
+from collections.abc import Callable
+from email import _ParamsType
 from email.mime.nonmultipart import MIMENonMultipart
 from email.policy import Policy
-from typing import Callable, Union
 
 __all__ = ["MIMEAudio"]
 
-_ParamsType = Union[str, None, tuple[str, str | None, str]]
-
 class MIMEAudio(MIMENonMultipart):
     def __init__(
         self,

stdlib/email/mime/base.pyi

@@ -1,10 +1,8 @@
 import email.message
+from email import _ParamsType
 from email.policy import Policy
-from typing import Union
 
 __all__ = ["MIMEBase"]
 
-_ParamsType = Union[str, None, tuple[str, str | None, str]]
-
 class MIMEBase(email.message.Message):
     def __init__(self, _maintype: str, _subtype: str, *, policy: Policy | None = ..., **_params: _ParamsType) -> None: ...

stdlib/email/mime/image.pyi

@@ -1,11 +1,10 @@
+from collections.abc import Callable
+from email import _ParamsType
 from email.mime.nonmultipart import MIMENonMultipart
 from email.policy import Policy
-from typing import Callable, Union
 
 __all__ = ["MIMEImage"]
 
-_ParamsType = Union[str, None, tuple[str, str | None, str]]
-
 class MIMEImage(MIMENonMultipart):
     def __init__(
         self,

stdlib/email/mime/multipart.pyi

@@ -1,12 +1,11 @@
+from collections.abc import Sequence
+from email import _ParamsType
 from email.message import Message
 from email.mime.base import MIMEBase
 from email.policy import Policy
-from typing import Sequence, Union
 
 __all__ = ["MIMEMultipart"]
 
-_ParamsType = Union[str, None, tuple[str, str | None, str]]
-
 class MIMEMultipart(MIMEBase):
     def __init__(
         self,

stdlib/email/parser.pyi

@@ -1,14 +1,13 @@
 import email.feedparser
+from email import _MessageT
 from email.message import Message
 from email.policy import Policy
-from typing import BinaryIO, Callable, TextIO, TypeVar
+from typing import BinaryIO, Callable, TextIO
 
 __all__ = ["Parser", "HeaderParser", "BytesParser", "BytesHeaderParser", "FeedParser", "BytesFeedParser"]
 
-_M = TypeVar("_M", bound=Message)
-
-FeedParser = email.feedparser.FeedParser[_M]
-BytesFeedParser = email.feedparser.BytesFeedParser[_M]
+FeedParser = email.feedparser.FeedParser[_MessageT]
+BytesFeedParser = email.feedparser.BytesFeedParser[_MessageT]
 
 class Parser:
     def __init__(self, _class: Callable[[], Message] | None = ..., *, policy: Policy = ...) -> None: ...

stdlib/email/utils.pyi

@@ -1,7 +1,8 @@
 import datetime
 import sys
+from email import _ParamType
 from email.charset import Charset
-from typing import Union, overload
+from typing import overload
 
 __all__ = [
     "collapse_rfc2231_value",
@@ -21,7 +22,6 @@ __all__ = [
     "unquote",
 ]
 
-_ParamType = Union[str, tuple[str | None, str | None, str]]
 _PDTZ = tuple[int, int, int, int, int, int, int, int, int, int | None]
 
 def quote(str: str) -> str: ...