Bug #19540: Undefined variable error when combining modifier if with one-line pattern matching

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 3.2.1 (2023-02-08 revision 31819e82c8) [x86_64-linux]
• Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

[mehanoid (Oleg Grigorev)]

If I try to use modifier if with a one-line pattern matching, the variable assigned by the pattern cannot be used inside the expression to the left of the "if":

x if [1] in [x]
(irb):1:in `<main>': undefined local variable or method `x' for main:Object (NameError)

This is very unexpected behavior, because the code looks equivalent to the following:

if [1] in [x]
  x
end
=> 1

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Rejected

This isn't a bug, this is how Ruby works. It is unrelated to pattern matching, you get the same behavior for x if x = foo and x unless x = foo. It may be unexpected if you are not used to it, though.