Bug #19548: Ambiguous and confusing syntax for alias/undef arguments

• Status: Rejected
• Assignee: -
• Target version: -
• Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

[hurricup (Alexandr Evstigneev)]

This was introduced in https://bugs.ruby-lang.org/issues/8851 and looks really confusing at least because of bare /.
Here are 3 semantically similar methods, but feels like first two should not be valid:

def method1
  undef :*,<<,/,[]
  alias :* /
end

def method2
  undef :*,
    <<,
    /,
    []
  alias :*
  /
end

def method3
  undef :*
  undef :<<
  undef :/
  undef :[]
  alias :* :/
end

puts RubyVM::InstructionSequence.of(method :method1).disasm
puts RubyVM::InstructionSequence.of(method :method2).disasm
puts RubyVM::InstructionSequence.of(method :method3).disasm

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Rejected

This isn't a bug, nor does it appear to be introduced by #8851 (that added support for %s symbol literals with alias/undef, other symbol literals were already supported). undef and alias have always accepted symbols and bare words, so alias :* / and undef :*, / work, as do alias * / and undef *, /. Not allowing bare words would break existing code.