Feature #1141

assignment of variable in "right" if statement fails

Added by hagus (Luke Burton) about 8 years ago. Updated almost 6 years ago.

Target version:


In Ruby 1.8

p(x) if x=42
(irb):1: warning: found = in conditional, should be ==
NameError: undefined local variable or method `x' for main:Object
from (irb):1

In Ruby 1.9

$ irb19
irb(main):001:0> p (x) if (x=42)
NameError: undefined local variable or method x' for main:Object
from (irb):1
from /usr/local/bin/irb19:12:in

However, if you move the if statement to the line before, naturally everything works.

Should variable assignment in "right" if clauses be permitted? I think so, since it allows you to be fairly concise and not have to do:

if x = 42

"Right" if clauses are permitted because they read naturally, I assume. I'm not sure whether people regard variable assignment in this case as reading very "naturally", but there is at the very least a lack of consistency between this type of if clause, and the more regular type of if clause.

Related issues

Duplicated by Ruby trunk - Feature #4965: The problem of "print line if line = DATA.gets" Rejected 07/03/2011
Duplicated by Ruby trunk - Feature #6224: Make variables in if/unless conditions available to conditional statements Rejected 03/29/2012
Duplicated by Ruby trunk - Feature #8600: Recognize variables declared in if modifier at end of line Rejected 07/04/2013


#1 Updated by matz (Yukihiro Matsumoto) about 8 years ago

  • Status changed from Open to Rejected

local variable scope determined up to down, left to right. So a local variable first assigned in the condition of if modifier is not effective in the left side if body. It's a spec.


Also available in: Atom PDF