Issue #18242 has been updated by danh337 (Dan H).


@nobu I built your PR branch and confirmed that this new parsing works great with the `driver.rb` attached.

Will this patch have to wait for the 3.1.0 release? Sorry I'm not sure how the whole patching and backporting processes work. (But I'm pretty sure it can get complicated.) If these were syntax errors in the past, should the patch be safe for stable versions too?

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Feature #18242: Parser makes multiple assignment sad in confusing way
https://bugs.ruby-lang.org/issues/18242#change-94097

* Author: danh337 (Dan H)
* Status: Open
* Priority: Normal
----------------------------------------
Example:
``` ruby
a, b = 2, 1     if 1 < 2     # Works
a, b = [2, 1]   if 1 < 2     # Works
(a, b) = 2, 1   if 1 < 2     # Works
(a, b) = [2, 1] if 1 < 2     # Works
(a, b = [2, 1]) if 1 < 2     # Works
a, b = 2, 1     unless 2 < 1 # Works
a, b = [2, 1]   unless 2 < 1 # Works
(a, b) = 2, 1   unless 2 < 1 # Works
(a, b) = [2, 1] unless 2 < 1 # Works
(a, b = [2, 1]) unless 2 < 1 # Works
1 < 2   and a, b = 2, 1      # SyntaxError
1 < 2   and a, b = [2, 1]    # SyntaxError
1 < 2   and (a, b) = 2, 1    # SyntaxError
1 < 2   and (a, b) = [2, 1]  # SyntaxError
(1 < 2) and a, b = 2, 1      # SyntaxError
(1 < 2) and a, b = [2, 1]    # SyntaxError
(1 < 2) and (a, b) = 2, 1    # SyntaxError
(1 < 2) and (a, b) = [2, 1]  # SyntaxError
1 < 2   and (a, b = 2, 1)    # Works
1 < 2   and (a, b = [2, 1])  # Works
2 < 1   or a, b = 2, 1       # SyntaxError
2 < 1   or a, b = [2, 1]     # SyntaxError
2 < 1   or (a, b) = 2, 1     # SyntaxError
2 < 1   or (a, b) = [2, 1]   # SyntaxError
(2 < 1) or a, b = 2, 1       # SyntaxError
(2 < 1) or a, b = [2, 1]     # SyntaxError
(2 < 1) or (a, b) = 2, 1     # SyntaxError
(2 < 1) or (a, b) = [2, 1]   # SyntaxError
2 < 1   or (a, b = 2, 1)     # Works
2 < 1   or (a, b = [2, 1])   # Works
```
Based on the precedence rules I've been able to find, all of these should work.

Believe it or not, there are cases where using `and` or `or` in a stanza of lines is much more readable.

Should the parser allow all of these? See attached driver script to reproduce this output.

---Files--------------------------------
driver.rb (1.17 KB)
and-or-masgn-18242.diff (963 Bytes)


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