Fix decorator typing with _Decorator type alias

CHANGES.rst

@@ -1,5 +1,12 @@
 .. currentmodule:: click
 
+Version 8.1.5
+-------------
+
+Unreleased
+
+- Fix type annotations on the option and argument decorators. :issue:`2558`
+
 Version 8.1.4
 -------------
 

src/click/decorators.py

@@ -21,7 +21,6 @@
 R = t.TypeVar("R")
 T = t.TypeVar("T")
 _AnyCallable = t.Callable[..., t.Any]
-_Decorator: "te.TypeAlias" = t.Callable[[T], T]
 FC = t.TypeVar("FC", bound=t.Union[_AnyCallable, Command])
 
 
@@ -331,7 +330,7 @@ def _param_memo(f: t.Callable[..., t.Any], param: Parameter) -> None:
 
 def argument(
     *param_decls: str, cls: t.Optional[t.Type[Argument]] = None, **attrs: t.Any
-) -> _Decorator[FC]:
+) -> t.Callable[[FC], FC]:
     """Attaches an argument to the command.  All positional arguments are
     passed as parameter declarations to :class:`Argument`; all keyword
     arguments are forwarded unchanged (except ``cls``).
@@ -359,7 +358,7 @@ def decorator(f: FC) -> FC:
 
 def option(
     *param_decls: str, cls: t.Optional[t.Type[Option]] = None, **attrs: t.Any
-) -> _Decorator[FC]:
+) -> t.Callable[[FC], FC]:
     """Attaches an option to the command.  All positional arguments are
     passed as parameter declarations to :class:`Option`; all keyword
     arguments are forwarded unchanged (except ``cls``).
@@ -385,7 +384,7 @@ def decorator(f: FC) -> FC:
     return decorator
 
 
-def confirmation_option(*param_decls: str, **kwargs: t.Any) -> _Decorator[FC]:
+def confirmation_option(*param_decls: str, **kwargs: t.Any) -> t.Callable[[FC], FC]:
     """Add a ``--yes`` option which shows a prompt before continuing if
     not passed. If the prompt is declined, the program will exit.
 
@@ -409,7 +408,7 @@ def callback(ctx: Context, param: Parameter, value: bool) -> None:
     return option(*param_decls, **kwargs)
 
 
-def password_option(*param_decls: str, **kwargs: t.Any) -> _Decorator[FC]:
+def password_option(*param_decls: str, **kwargs: t.Any) -> t.Callable[[FC], FC]:
     """Add a ``--password`` option which prompts for a password, hiding
     input and asking to enter the value again for confirmation.
 
@@ -433,7 +432,7 @@ def version_option(
     prog_name: t.Optional[str] = None,
     message: t.Optional[str] = None,
     **kwargs: t.Any,
-) -> _Decorator[FC]:
+) -> t.Callable[[FC], FC]:
     """Add a ``--version`` option which immediately prints the version
     number and exits the program.
 
@@ -539,7 +538,7 @@ def callback(ctx: Context, param: Parameter, value: bool) -> None:
     return option(*param_decls, **kwargs)
 
 
-def help_option(*param_decls: str, **kwargs: t.Any) -> _Decorator[FC]:
+def help_option(*param_decls: str, **kwargs: t.Any) -> t.Callable[[FC], FC]:
     """Add a ``--help`` option which immediately prints the help page
     and exits the program.