[ruby-core:94450] [Ruby master Bug#10388] Operator precedence problem in multiple assignment (massign)

[merch-redmine@jeremyevans.net]

Issue #10388 has been updated by jeremyevans0 (Jeremy Evans).


I tried working on this a couple weeks ago and I don't believe the current LALR(1) parser can support it.  Attempting to modify the parser to support the behavior you desire leads to many shift/reduce or reduce/reduce conflicts.  It is possible that switching from the default LALR(1) parser to a GLR parser (which bison also supports) may allow for the behavior your desire, but I'm not sure what the ramifications of that are.  It's also possible there is a way to introduce this behavior with the existing LALR(1) parser, and I am just not aware of it, as I do not have much experience in this area.

----------------------------------------
Bug #10388: Operator precedence problem in multiple assignment (massign)
https://bugs.ruby-lang.org/issues/10388#change-80880

* Author: knu (Akinori MUSHA)
* Status: Open
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 
* ruby -v: ruby 2.2.0dev (2014-10-13 trunk 47904) [x86_64-freebsd10]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
----------------------------------------
I understand it wouldn't be easy to fix this, but since I happened to find it here it goes.

- `a, b = c = 1, 2` is currently taken as `a, b = (c = 1), 2`; I'd expect it to be taken as `a, b = (c = 1, 2)`.

- `a, b = *c = 1, 2` is currently taken as `a, b = *(c = 1), 2`; I'd expect it to be taken as `a, b = *(c = 1, 2)` or even `a, b = (*c = 1, 2)`.

- `a, b = c, d = 1, 2` is currently taken as `a, b = (c), (d = 1), 2`; I'd expect it to be taken as `a, b = (c, d = 1, 2)`.

Should they be fixed/changed or not, issuing a warning would be greatly helpful.



-- 
https://bugs.ruby-lang.org/