Cloning breaks constant resolution

[XrXr]

class Foo
  def test
    TEST
  end
end

Bar1 = Foo.clone
Bar1::TEST = 1
p Bar1.new.test # 1 on MRI 2.4.x ~ 3.0.0, NameError on TruffleRuby 21.0.0

[chrisseaton]

Thanks very much for reporting that. I'd never considered cloned classes, myself!

[bjfish]

I suspect we are missing updating the lexical scope during the copy:
https://github.com/ruby/ruby/blob/7332b3f367ce61089bf571fa1c458fde06a11eab/class.c#L253
https://github.com/ruby/ruby/blob/7332b3f367ce61089bf571fa1c458fde06a11eab/vm_insnhelper.c#L801

[eregon]

Right, I guessed that as well.
The issue is we capture the LexicalScope in the AST so:

• it's hard to change it (e.g., it's stored as part of ReadConstantWithLexicalScopeNode)
• it would mean copying the AST and a new CallTarget, which seems fairly expensive

We might need to change how we pass the lexical scope for AST Sharing (#1835), so maybe that change will make it easier to fix this.

Is there real-world code depending on this? (I'm trying to judge how important it is to fix soon)

[XrXr]

I don't know any real-world code that depend on this.