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fatal typing error with local module + functor + polymorphic variant #5057

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vicuna opened this Issue May 20, 2010 · 1 comment

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vicuna commented May 20, 2010

Original bug ID: 5057
Reporter: @ygrek
Status: closed (set by @garrigue on 2010-05-21T01:27:44Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 3.11.2
Fixed in version: 3.12.0+dev
Category: ~DO NOT USE (was: OCaml general)

Bug description

$ cat bug.ml

module TT = struct
module IntSet = Set.Make(struct type t = int let compare = compare end)
end

let () =
let f flag =
let module T = TT in
let _ = match flag with A -> 0 | B r -> r in
let _ = match flag with A -> T.IntSet.mem | B r -> r in
()
in
f ()

$ ocamlc -c bug.ml
Fatal error: exception Ctype.Unify(_, _)

$ ocamlc -version
3.11.2

Additional information

This is a minimized example, originally occurred in real sensible code.
Also reported to fail in 3.12.0+dev17

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vicuna commented May 21, 2010

Comment author: @garrigue

The correct code should be "f `A" :-)

There was a bug in the handling of levels inside polymorphic variant fields.
This is now fixed for 3.12.
Note that your report helped discover a more serious problem, where the following
code was wrongly accepted. Thank you very much.

let f flag =
let module T = Set.Make(struct type t = int let compare = compare end) in
let _ = match flag with A -> 0 | B r -> r in
let _ = match flag with A -> T.mem | B r -> r in
()

@vicuna vicuna closed this May 21, 2010

@vicuna vicuna added the bug label Mar 20, 2019

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