Different behavior between TruffleRuby and CRuby

[Maumagnaguagno]

The following code has different behavior in TruffleRuby 22.1.0 and CRuby 3.1.2.

a = [1,2,3]
h = {}
until a.empty?
  p a
  h[a.shift] ||= false
end
p h

See outputs below:

# CRuby
[1, 2, 3]
[2, 3]
[3]
{1=>false, 2=>false, 3=>false}

# TruffleRuby
[1, 2, 3]
[3]
{2=>false, nil=>false}

To my surprise, replacing ||= with = makes both Rubies output the same. Forgive me if this is already fixed or if there is a related open issue, my search resulted in nothing similar.

[eregon]

This is because the a.shift is evaluated twice by TruffleRuby, but only once by CRuby. We should fix that.

This variant has no issue:

a = [1,2,3]
h = {}
until a.empty?
  p a
  e = a.shift
  h[e] ||= false
end
p h

[aardvark179]

Our translation of operator assignment nodes seems half correct. We correctly store the receiver as a local variable, but we do not do this correctly with any arguments passed to that receiver.

[aardvark179]

The fix for this has now been merged into master.