From: recursive.madman@...
Date: 2014-12-18T12:10:47+00:00
Subject: [ruby-core:66947] [ruby-trunk - Bug #10450] multiple assignment in	conditional

Issue #10450 has been updated by Recursive Madman.


Actually, thinking about it again I'm not sure anymore if the warning is warranted. The warning for singular assignment is there to warn about the possibility of a typo (`a = b` vs `a == b`). Multiple assignment is unambiguous in this respect though (`a, b = c` makes sense, `a, b == c` doesn't).

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Bug #10450: multiple assignment in conditional
https://bugs.ruby-lang.org/issues/10450#change-50490

* Author: bug hit
* Status: Rejected
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: ruby 2.1.4p265 (2014-10-27 revision 48166) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
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multiple assignment is an expression whose value can be truthy (array) or falsy (nil, false), so why is there a restriction on its use in conditionals?  A warning perhaps is justified, but a syntax error, why?


irb(main):001:0> if a, b = nil then 1 else 0 end
SyntaxError: (irb):1: syntax error, unexpected ',', expecting keyword_then or ';' or '\n'
if a, b = nil then 1 else 0 end
     ^
(irb):1: syntax error, unexpected keyword_then, expecting end-of-input
if a, b = nil then 1 else 0 end
                  ^
	from /home/alex/.rbenv/versions/2.1.4/bin/irb:11:in `<main>'
irb(main):002:0> if (a, b = nil) then 1 else 0 end
SyntaxError: (irb):2: multiple assignment in conditional
	from /home/alex/.rbenv/versions/2.1.4/bin/irb:11:in `<main>'
irb(main):003:0> (a, b = nil) ? 1 : 0
SyntaxError: (irb):3: multiple assignment in conditional
	from /home/alex/.rbenv/versions/2.1.4/bin/irb:11:in `<main>'
irb(main):004:0> (a, b = nil)
=> nil




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