PEP 749: Add annotations_to_source, value_to_source (#3998)

Author: JelleZijlstra

peps/pep-0749.rst

@@ -221,6 +221,16 @@ The module will contain the following functionality:
   dictionary. This is intended to be used for evaluating deferred attributes introduced by
   :pep:`695` and :pep:`696`; see below for details. *func* may be ``None``
   for convenience; if ``None`` is passed, the function also returns ``None``.
+* ``annotations_to_source(annotations: dict[str, object]) -> dict[str, str]``: a function that
+  converts each value in an annotations dictionary to a string representation.
+  This is useful for
+  implementing the ``SOURCE`` format in cases where the original source is not available,
+  such as in the functional syntax for :py:class:`typing.TypedDict`.
+* ``value_to_source(value: object) -> str``: a function that converts a single value to a
+  string representation. This is used by ``annotations_to_source``.
+  It uses ``repr()`` for most values, but for types it returns the fully qualified name.
+  It is also useful as a helper for the ``repr()`` of a number of objects in the
+  :py:mod:`typing` and :py:mod:`collections.abc` modules.
 
 A new function is also added to the :py:mod:`!typing` module, ``typing.evaluate_forward_ref``.
 This function is a wrapper around the ``ForwardRef.evaluate`` method, but it performs