Crystal: Can't declare method ==(*args)

[BrucePerens]

This code:

class Foo
  def ==(*args)
    true
  end
end

won't compile, with the error:

crystal build foo.cr
In foo.cr:2:16

 2 | def ==(*args)
                  ^
Error: setter method '==' cannot have more than one argument

First, the error message is odd since == isn't a setter. Also, although *args is a catch-all for positional arguments, it isn't forcing the compiler to provide more than one argument to ==.

The reason I hit this is that I have my own delegate macro that does optional argument and return-value processing. I hacked in a one_argument option so that I could successfully delegate ==. I can't see why Object#delegate doesn't need to do this, unless there is compiler magic going on.

[straight-shoota]

The error message can be improved, but the behaviour seems correct. Equality method requires exactly one argument, so a splat makes really no sense. The compiler should call that out.

Object#delegate handles methods ending in = explicitly:
https://github.com/crystal-lang/crystal/blob/48ebe7b809ebebc6a2360d043b58726a569533f2/src/object.cr#L1247