Re: [Caml-list] polymorphic methods

[Leo White <leo@lpw25.net>]

Hi,

This probably constitutes a bug, seeing as the problem only occurs when using a type alias:

# class foo = object
    method f : 'a 'b. (< x: 'b; ..> as 'a) -> 'b = assert false
  end;;
    class foo : object method f : < x : 'b; .. > -> 'b end

# type ('a, 'b) f_arg = < x : 'b; .. > as 'a;;
type ('a, 'b) f_arg = 'a constraint 'a = < x : 'b; .. >

# class foo = object
    method f : 'a 'b. ('a, 'b) f_arg -> 'b = assert false
  end;;
    Characters 30-76:
      method f : 'a 'b. ('a, 'b) f_arg -> 'b = assert false
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: This expression has type 'a 'b. (< x : 'b; .. > as 'a, 'b) f_arg -> 'b
       but an expression was expected of type
         'c 'b. (< x : 'b; .. > as 'c, 'b) f_arg -> 'b
       The type variable 'd occurs inside 'd

Regards,

Leo