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Private constraints accepted by toplevel but not by compiler #4623

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vicuna opened this Issue Oct 15, 2008 · 2 comments

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commented Oct 15, 2008

Original bug ID: 4623
Reporter: dario
Assigned to: @garrigue
Status: closed (set by @garrigue on 2010-04-27T07:16:51Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 3.11+dev
Fixed in version: 3.11+dev
Category: ~DO NOT USE (was: OCaml general)
Related to: #4580

Bug description

Using the just released 3.11 Beta1, the following code is accepted by the top-level:

module Foobar:
sig
type foo_t = [ A ] type bar_t = [ B ]
type foobar_t = [ foo_t | bar_t ]
type 'a t = private 'a constraint 'a = [< foobar_t ]

    val make_a: unit -> foo_t t
    val make_b: unit -> bar_t t

end =
struct
type foo_t = [ A ] type bar_t = [ B ]
type foobar_t = [ foo_t | bar_t ]
type 'a t = 'a constraint 'a = [< foobar_t ]

    let make_a () = `A
    let make_b () = `B

end

But is rejected by both the byte and native code compilers:

File "constraint.ml", line 1, characters 0-1:
Error: The implementation constraint.ml
does not match the interface (inferred signature):
Modules do not match:
sig
type foo_t = [ A ] type bar_t = [ B ]
type foobar_t = [ A | B ]
type 'a t = 'a Foobar.t constraint 'a = [< foobar_t ]
val make_a : unit -> foo_t t
val make_b : unit -> bar_t t
end
is not included in
sig
type foo_t = [ A ] type bar_t = [ B ]
type foobar_t = [ A | B ]
type 'a t = private 'a constraint 'a = [< foobar_t ]
val make_a : unit -> foo_t t
val make_b : unit -> bar_t t
end
Type declarations do not match:
type 'a t = 'a Foobar.t constraint 'a = [< foobar_t ]
is not included in
type 'a t = private 'a constraint 'a = [< foobar_t ]

@vicuna

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commented Oct 16, 2008

Comment author: @garrigue

Actually the problem was not unrelated to constraints.
A minimal reproduction case follows:

module Foobar : sig type t = private int end =
struct type t = int end

This is now fixed in CVS/release311, by allowing head-expansion of private
abbreviations when defining a private type.

@vicuna

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commented Apr 27, 2010

Comment author: @garrigue

safe to close

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