Bug #19166: Module#remove_method can change frozen modules when there is a prepended module

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: 2.7, 3.0, 3.1, dev
• Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN

[alanwu (Alan Wu)]

module A
  prepend Module.new # remove this line and you'd get FrozenError as expected
  def foo; end
  freeze
  remove_method :foo # remove works even though module is frozen!
  p instance_methods(false) # => []
end

Old bug, reproduces in 2.7 through 3.1 and on master. Found while investigating #19164.

[Eregon (Benoit Daloze)]

• Related to Bug #19164: [3.2.0dev] Freezing an object can prevent removing methods on its class added

• Status changed from Open to Closed

Applied in changeset git|3d272b0fc822f5c2e9c716377b7fcecf15426b27.

---

Module#remove_method: Check frozen on the right object

Previously, the frozen check happened on RCLASS_ORIGIN(self), which
can return an iclass. The frozen check is supposed to respond to objects
that users can call methods on while iclasses are hidden from users.
Other mutation methods like Module#{define_method,alias_method,public}
don't do this. Check frozen status on the module itself.

Fixes [Bug #19164] and [Bug #19166].

Co-authored-by: Alan Wu [e-mail]