Add separate doc/syntax/pattern_matching.rdoc, add
link to control_expressions.rdoc.
The documentation is "reverse-engineered" from Ruby 2.7
behavior and early preview presentations, and corrected
by pattern-matching feature author @k-tsj.
In the grammar, all expressions are statements, but not all
statements are expressions. Some parts of the grammar accept
expressions and not other types of statements, which causes
similar looking code to parse differently due to operator
precedence.
Mostly from Dan0042 (Daniel DeLorme).
Fixes [Bug #16092]
unless expressions. Improved description of "a if a = 0.zero?"
NameError. Note that "do" for for loop is optional.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38844 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
