On Wed, Aug 30, 2023 at 11:53 AM Xavier Noria <fxn@hashref.com> wrote:
(a, b) does not play the role of an expression, right? Similarly, in your
examples with puts,
puts(...)
is parsed as puts + the argument list of the call. Again, not an
expression. In an argument list, a semicolon does not make sense, it is a syntax error.
My example had a space between puts and '('. The documentation says: "If you put a space between the method name and opening parenthesis, you do not need two sets of parentheses." but 'puts (:ignore; :x)' raises an error.
Oh, the space, right.
p (1 if true), (2 if false)
passes two arguments to p just fine.
The specs for this are here <https://github.com/ruby/ruby/blob/00fdb4e12e1933bdb110aeecc08099b4875c91ce/spec/ruby/language/method_spec.rb#L1178> (an authoritative source when documentation is lacking), and I cannot give you an answer to what you found without guessing. It could even be a bug in the parser, because I don't quite see why is a ternary operator parsed, but not an expression with ;.
I don't know.
I have opened https://github.com/ruby/spec/pull/1063. If it goes in, it is intentional, but it is not related to the syntax for arbitrary expressions. I exchanged impressions with Kevin Newton, and making parantheses optional in that corner of the grammar is special-cased for single statements. Let's see what we find out!