[ruby-core:104649] [Ruby master Feature#18040] Why should `foo(1 if true)` be an error?
From:
merch-redmine@...
Date:
2021-07-19 20:41:54 UTC
List:
ruby-core #104649
Issue #18040 has been updated by jeremyevans0 (Jeremy Evans). bughit (bug hit) wrote in #note-5: > jeremyevans0 (Jeremy Evans) wrote in #note-4: > > You may want to read the definition of `stmt` in parse.y, particularly this part: https://github.com/ruby/ruby/blob/eed5e8f796ab18e2e0a436dab83e35504ae3ded0/parse.y#L1481 > > You can call it a statement all you want but if it produces a value, its an expression. And it does produce a value. The reason that `foo(1 if false)` is a syntax error is due to a parsing failure. The parser considers it a statement (`stmt`) and not an expression. What the parser considers statements can still return values in Ruby. In any case, the reason for the issue remains the same. The parser doesn't allow a statement (`stmt`) to be used directly as a method argument. You have to wrap it in parentheses to use it as a method argument. Trying to support a `stmt` used directly as a method argument (`arg`), results in 132 shift/reduce conflicts and 2056 reduce/reduce conflicts in the parser. I doubt there is any way to support it as a general method argument. As I mentioned it may be possible to get it to work in only the single argument case by special casing it. However, I couldn't get that to work without shift/reduce conflicts. Maybe @nobu would have more luck. Even then, we would have to decide if we want to support that, because it would result in inconsistent syntax, since `foo(1 if false)` would be allowed, but `foo(1 if false, 2)` (the multiple argument case) would not. ---------------------------------------- Feature #18040: Why should `foo(1 if true)` be an error? https://bugs.ruby-lang.org/issues/18040#change-92958 * Author: bughit (bug hit) * Status: Open * Priority: Normal ---------------------------------------- There's no ambiguity here that should require another set of parens `foo((1 if true))` -- https://bugs.ruby-lang.org/ Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe> <http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>