Feedback

- reduce Semantics section

Author: Daraan

peps/pep-0821.rst

@@ -84,28 +84,21 @@ Additionally, positional parameters may be combined with an unpacked
 Semantics
 ---------
 
-* Each key in the ``TypedDict`` must be accepted as a keyword parameter.
-* TypedDict keys cannot be positional-only; they must be valid keyword
-  parameters.
+For type-checking purposes, ``Callable[Unpack[TD], R]`` behaves as if it were
+specified via a callback protocol whose ``__call__`` method has
+``**kwargs: Unpack[TD]``.
+The semantics of ``Unpack`` itself are exactly those described in the typing
+specification's `Unpack for keyword arguments
+<https://typing.python.org/en/latest/spec/callables.html#unpack-for-keyword-arguments>`_
+section and :pep:`692`, together with :pep:`728` for ``extra_items`` and
+``closed``.
+
+This PEP only adds the following Callable-specific rules:
+
+* ``Unpack[TD]`` may appear inside the parameter list of
+  ``Callable``.
 * Positional parameters may appear in ``Callable`` before ``Unpack[TD]`` and
-  follow normal ``Callable`` semantics.
-* Required keys must be accepted, but may correspond to parameters with a
-  default value.
-* ``NotRequired`` keys must still be accepted, but may be omitted at call sites.
-  This respectively applies to ``TypedDict`` with ``total=False``.
-* Functions with ``**kwargs`` are compatible if the annotation of ``**kwargs``
-  matches or is a supertype of the ``TypedDict`` values.
-* ``extra_items`` from :pep:`728` is respected: functions accepting additional
-  ``**kwargs`` are valid if their annotation is compatible with the declared
-  type.
-* If neither ``extra_items`` nor ``closed`` (:pep:`728`) is specified on the
-  ``TypedDict``, additional keyword arguments are implicitly permitted with
-  type ``object`` (i.e., compatible with ``**kwargs: object``). Setting
-  ``closed=True`` forbids any additional keyword arguments beyond the keys
-  declared in the ``TypedDict``. Setting ``extra_items`` to a specific type
-  requires that any additional keyword arguments match that type.
-* Only a single ``TypedDict`` may be unpacked inside a ``Callable``. Support
-  for multiple unpacks may be considered in the future.
+  follow existing ``Callable`` semantics.
 
 Examples
 --------
@@ -281,9 +274,13 @@ taught that with ::
   ``__call__(self, **kwargs: Unpack[Signature]) -> R``
   or
   ``__call__(self, a: int, b: str = ..., **kwargs: object) -> R``.
+* Teachers might want to introduce the concept of ``TypedDict`` with
+  ``Callable`` first before introducing ``Protocol``.
 * The implicit addition of ``**kwargs: object`` might come surprising to users,
   using ``closed=True`` for definitions will create the more intuitive
   equivalence of ``__call__(self, a: int, b: str = ...) -> R``
+* Users should be made aware of the interaction with ``extra_items`` from
+  :pep:`728`.
 
 
 Reference Implementation
@@ -311,9 +308,6 @@ Open Questions
   how to handle overlapping keys of non-identical types? Which restrictions
   should apply in such a case? Should the order matter?
 * Is there a necessity to differentiate between normal and ``ReadOnly`` keys?
-* Is it necessary to specify generic behavior for ``TypedDict`` and the
-  resulting ``Callable`` when the ``TypedDict`` itself is generic?
-
 
 Acknowledgements
 ================