PEP 622: Clarifications that came up on python-dev

- State that `case` is also a soft keyword
- Triple-quoted strings are supported
- Clarify that `__match__` must be a static or class method returning an object or None
- Add two TODOs
- Fix line of dashes

pep-0622.rst

@@ -157,9 +157,10 @@ many languages it is an expression, being a statement better suits the general
 logic of Python syntax. See `rejected ideas`_ for more discussion. The list of
 allowed patterns is specified below in the `patterns`_ subsection.
 
-The ``match`` word is proposed to be a soft keyword, so that it is recognized
-as a keyword at the beginning of a match statement, but is allowed to be used in
-other places as a variable or argument name.
+The ``match`` and ``case`` keywords are proposed to be soft keywords,
+so that they are recognized as keywords at the beginning of a match
+statement or case block respectively, but are allowed to be used in
+other places as variable or argument names.
 
 The proposed indentation structure is as following::
 
@@ -236,7 +237,7 @@ literals for the purpose of pattern matching. Unary plus is not allowed.
 Binary plus and minus are allowed only to join a real number and an imaginary
 number to form a complex number, such as ``1+1j``.
 
-Raw strings and byte strings
+Triple-quoted strings are supported.  Raw strings and byte strings
 are supported. F-strings are not allowed (since in general they are not
 really literals).
 
@@ -544,9 +545,15 @@ Runtime specification
 The ``__match__()`` protocol
 ----------------------------
 
-The ``__match__()`` method is used to decide whether an object matches a given
-class pattern and to extract the corresponding attributes. The procedure is as
-following:
+TODO: Show equivalent pseudo code.
+
+The ``__match__()`` method is used to decide whether an object matches
+a given class pattern and to extract the corresponding attributes.  It
+must be a class method or a static method returning an object
+(typically the same as the argument), or ``None`` to indicate that no
+match is possible.  (More about the return value in the next section.)
+
+The procedure is as following:
 
 * The class object for ``Class`` in ``Class(<sub-patterns>)`` is looked up and
   ``Class.__match__(obj)`` is called where ``obj`` is the value being matched.
@@ -684,7 +691,7 @@ required.
 
 
 The standard library
-------------------------------------
+--------------------
 
 To facilitate the use of pattern matching, several changes will be made to
 the standard library:
@@ -1157,6 +1164,8 @@ In sample programs using `match`, written as part of the development of this
 PEP, a noticeable improvement in code brevity is observed, more than making up
 for the additional indentation level.
 
+TODO: flat indentation with "match: expression" at the top.
+
 
 Alternatives for constant value pattern
 ---------------------------------------