Apply suggestions from code review

Thanks Alex! Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
python · JelleZijlstra · Apr 25, 2022 · Apr 20, 2022 · Apr 21, 2022 · Apr 21, 2022
commit 8d63329dbcb125bb476703e2cb67423870022a4e
@@ -2341,14 +2341,17 @@ Functions and decorators
               case _ as unreachable:
                   assert_never(unreachable)

-   Here, the type annotations allow the type checker to infer that the
+   Here, the annotations allow the type checker to infer that the
   last case can never execute, because ``arg`` is either
   an :class:`int` or a :class:`str`, and both options are covered by
   earlier cases.
   If a type checker finds that a call to ``assert_never()`` is
   reachable, it will emit an error. For example, if the type annotation
   for ``arg`` was instead ``int | str | float``, the type checker would
   emit an error pointing out that ``unreachable`` is of type :class:`float`.
+   For a call to ``assert_never`` to succeed, the inferred type of
+   the argument passed in must be the bottom type, :data:`Never`, and nothing
+   else.

   At runtime, this throws an exception when called.