[ruby-core:76395] [Ruby trunk Feature#12593] Allow compound assignements to work when destructuring arrays

Issue #12593 has been reported by Naja Melan.

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Feature #12593: Allow compound assignements to work when destructuring arrays
https://bugs.ruby-lang.org/issues/12593

* Author: Naja Melan
* Status: Open
* Priority: Normal
* Assignee: 
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~~~ ruby
a = [ 'a', 'b' ]
b = [ 'c', 'd' ]

def c

    return [ 'A', 'B' ], [ 'C', 'D' ]

end

a, b += c # -> would be awesome, but gives syntax error

a, b = a + c.first, b + c.last # clunky and will call method twice...

# current realistic use:
t, tt = c
a += t
b += tt

# desired result
#
p a == [ 'a', 'c', 'A', 'B' ] #-> true
p b == [ 'b', 'd', 'C', 'D' ] #-> true
~~~

I would propose that as 

~~~ ruby
a, b = [ c, d ] # is equivalent to:
a = c 
b = d

a, b += [ c, d ] # would be equivalent to:
a += c
b += d
~~~

This not working surprised me. It could work with all compound assignment operators I think. Maybe even with some other operators.




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