Bug #21535: `NoMethodError` becomes `NameError`when using `...` delegation and method call indirection

• Status: Open
• Assignee: -
• Target version: -
• ruby -v: ruby 3.5.0dev (2025-08-08T02:57:23Z master 3ad26d0501) +PRISM [x86_64-linux]
• Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN

[Earlopain (Earlopain _)]

Consider this code:

class Test
  def foo(...)
    nil.foo(...)
  end

  def foo_indirect
    foo
  end
end

begin
  Test.new.foo
rescue => e
  puts e.class
end

begin
  Test.new.foo_indirect
rescue => e
  puts e.class
end

$ ruby -v foo.rb 
ruby 3.3.6 (2024-11-05 revision 75015d4c1f) [x86_64-linux]
NoMethodError
NoMethodError

$ ruby -v foo.rb 
ruby 3.5.0dev (2025-08-08T02:57:23Z master 3ad26d0501) +PRISM [x86_64-linux]
NoMethodError
NameError

On ruby 3.3 it used to always raise a NoMethodError. Starting with Ruby 3.4, it raises a NoMethodError when calling the method directly, and a NameError when the method is called indirectly via a different method.

The context is the delegate method from rails (original issue https://github.com/rails/rails/issues/55463), which rescues the NoMethodError to raise a more specific error class.

The problem is the ... delegation. If the method accepts no arguments, *, **, or something else, it behaves as expected.

[Earlopain (Earlopain _)]

Maybe https://bugs.ruby-lang.org/issues/21196 is of relevance