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GADT constructors can be re-exposed with an incompatible type => segfault #7378

vicuna opened this issue Sep 28, 2016 · 1 comment


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commented Sep 28, 2016

Original bug ID: 7378
Reporter: @alainfrisch
Assigned to: @garrigue
Status: resolved (set by @garrigue on 2016-09-28T10:42:12Z)
Resolution: fixed
Priority: high
Severity: major
Target version: 4.04.0 +dev / +beta1 / +beta2
Fixed in version: 4.04.0 +dev / +beta1 / +beta2
Category: typing
Child of: #5998

Bug description

module X = struct
  type t =
    | A : 'a * 'b * ('a -> unit) -> t

module Y = struct
  type t = X.t =
    | A : 'a * 'b * ('b -> unit) -> t

let () =
  match Y.A (1, "", print_string) with
  | X.A (x, y, f) -> f x

The definition for Y.t should be rejected, but it's not, leading to a segfault further down.


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commented Sep 28, 2016

Comment author: @garrigue

Fixed in 4.04 by commit 10301ac

In presence of existential type variables in the definition, it is essential that Ctype.equal be called on all argument types simultaneously.
I kind of recall fixing that once before, so I left a comment about it in

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