[ruby-core:66877] [ruby-trunk - Bug #10450] multiple assignment in conditional

Issue #10450 has been updated by Recursive Madman.


It is indeed weird, that this isn't allowed.

A few lines below where the parse error is thrown, there is

```
parser_warn(node->nd_value, "found = in conditional, should be ==");
```

for regular conditionals.

It seems weird to me, that one is a warning and the other is an error, when the parser has at that point already recognized the multiple assignment correctly.

The warning suggests that assignment in conditionals is discouraged. That doesn't explain though, why one is an error and the other is not.

----------------------------------------
Bug #10450: multiple assignment in conditional
https://bugs.ruby-lang.org/issues/10450#change-50430

* 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
----------------------------------------
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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