Add None-assert operator to deferred ideas

Author: cdce8p

peps/pep-0823.rst

@@ -587,6 +587,19 @@ hierarchies.
 
 A workaround would be to write ``a.foo?.__call__(arguments)``.
 
+``None``-assert operator
+------------------------
+
+Some languages with "``null``-aware" operators also have a "``not-null``
+assertion" operator ``!``, e.g. TypeScript [#ts_non_null]_ and Dart [#dart]_.
+It was proposed to add a "``None``-assert" operator ``!``. This would
+be especially useful in typed Python code where type checkers are not
+able to statically deduce that a variable, with an ``optional`` (can be
+``None``) value, cannot be ``None`` in some contexts.
+
+This PEP focuses on the ``None``-aware access operators and therefore
+this proposal is out of scope.
+
 Add ``list.get(key)``
 ---------------------
 
@@ -1190,6 +1203,8 @@ Footnotes
    (https://discuss.python.org/t/introducing-a-safe-navigation-operator-in-python/35480)
 .. [#ts] TypeScript: Optional Chaining
    (https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#optional-chaining)
+.. [#ts_non_null] TypeScript: Non-null Assertion Operator
+   (https://www.typescriptlang.org/docs/handbook/2/everyday-types.html#non-null-assertion-operator-postfix-)
 .. [#js] JavaScript: Optional chaining (?.)
    (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining)
 .. [#js_short_circuiting] JavaScript: Optional chaining (?.) - Short-circuiting