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type abbreviation hides constraints #2325

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vicuna opened this Issue Dec 20, 1999 · 2 comments

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vicuna commented Dec 20, 1999

Original bug ID: 3
Reporter: administrator
Status: closed
Resolution: fixed
Priority: normal
Severity: minor
Category: ~DO NOT USE (was: OCaml general)

Bug description

Full_Name: Hendrik Tews
Version: 2.02
OS:
Submission from: estephe.inria.fr (128.93.11.95)
Submitted by: xleroy

Hi,

if I type

# class type ['a] cta = object val a_val : 'a method b : int end;;
# class ['a] ca (a:'a) : ['a] cta =
   object val a_val = a method b = a_val#get + 5 end;; 

into the toplevel, the system derives the type

class ['a] ca : 'a -> ['a] cta 

IMO this is wrong, because there must be a constraint for the type
parameter of class ca (the constraint becomes visible, if the
type annotation ['a] cta is left out). The problem becomes even
more apparent, when the system derives for

# module M = struct class ['a] ca (a:'a) : ['a] cta =
  object val a_val = a method b = a_val#get + 5 end end ;;

the type

  module M : sig class ['a] ca : 'a -> ['a] cta end

because

# module type MT = sig class ['a] ca : 'a -> ['a] cta end;;
# module M : MT = struct class ['a] ca (a:'a) : ['a] cta =
  object val a_val = a method b = a_val#get + 5 end end ;;

produces an error.

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vicuna commented Nov 19, 2001

Comment author: administrator

Hello,

I have finally closed #2325.
The fix was much simpler than what I thought, but it is somehow weak:
all classes whose parameters have constraints will not be abbreviated,
independently of wether the abbreviation is correct or not.

Jacques Garrigue

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vicuna commented Nov 19, 2001

Comment author: administrator

Fixed by Jacques on 2001-11-19.

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