do not parse `|` as infix in patterns; parse `|}` as `|` `}`

* use mixfix `(p1 | … | pn)` notation for nested disjunctive patterns,
rather than infix `|`, making pattern syntax consistent with term
syntax.
* disable extending `pattern` grammar with notation incompatible with
the nested disjunctive pattern syntax `(p1 | … | pn)`, such as the `(p
| q)` divisibility notation used by `Numbers`.
* emit a (disabled by default) `disj-pattern-notation` warning when such
`Notation` is attempted.
* update documentation accordingly; document incompatibilities in
`changelog`.
* comment special treatment of `(num)` in grammar.
* update file extensions in `Pcoq` header comment.
* correct the keyword declarations to reflect the contents of the
grammar files; perhaps there should be an option to disable implicit
keyword extension in a `.mlg` file, so that these lists could actually
be checked.
* parse the `|}` manifest record terminator as `|` followed by `}`,
eliminating the `|}` token which conflicts with notations that use `|`
as a terminator (such as, absolute value, norm, or cardinal in
MathComp). Since `|` is now an `operconstr` _and_ `pattern` terminator,
`bar_cbrace` rule checks for contiguous symbols, this change entails no
visible behaviour change.

1 files changed, 4 insertions, 3 deletions

diff --git a/doc/sphinx/addendum/extended-pattern-matching.rst b/doc/sphinx/addendum/extended-pattern-matching.rst
index e882ce6e88..b568160356 100644
--- a/doc/sphinx/addendum/extended-pattern-matching.rst
+++ b/doc/sphinx/addendum/extended-pattern-matching.rst
@@ -21,10 +21,10 @@ type is considered to be a variable. A variable name cannot occur more
 than once in a given pattern. It is recommended to start variable
 names by a lowercase letter.
 
-If a pattern has the form ``(c x)`` where ``c`` is a constructor symbol and x
+If a pattern has the form ``c x`` where ``c`` is a constructor symbol and x
 is a linear vector of (distinct) variables, it is called *simple*: it
 is the kind of pattern recognized by the basic version of match. On
-the opposite, if it is a variable ``x`` or has the form ``(c p)`` with ``p`` not
+the opposite, if it is a variable ``x`` or has the form ``c p`` with ``p`` not
 only made of variables, the pattern is called *nested*.
 
 A variable pattern matches any value, and the identifier is bound to
@@ -216,7 +216,8 @@ Here is an example:
      end.
 
 
-Here is another example using disjunctive subpatterns.
+Nested disjunctive patterns are allowed, inside parentheses, with the
+notation :n:`({+| @pattern})`, as in:
 
 .. coqtop:: in