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OCaml declare type as weak. It is not. #7782

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vicuna opened this Issue Apr 20, 2018 · 1 comment

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vicuna commented Apr 20, 2018

Original bug ID: 7782
Reporter: sagotch
Assigned to: @Octachron
Status: resolved (set by @Octachron on 2018-04-20T08:51:32Z)
Resolution: not a bug
Priority: normal
Severity: minor
Platform: Mac
OS: Mac OS
OS Version: 10.13.4
Version: 4.06.1
Category: typing

Bug description

let for_all =
let module IntSet =
Set.Make (struct type t = int let compare = Pervasives.compare end)
in
fun fn data ->
let maybe_update acc i v = if fn v then acc else IntSet.add i acc in
let init =
let rec fold i acc = function
| v :: tl -> fold (i + 1) (maybe_update acc i v) tl
| [] -> acc
in
fold 0 IntSet.empty
in
let update_idx_after i f acc =
IntSet.map (fun i' -> if i' >= i then f i' 1 else i') acc
in
let f = fun acc -> function
| Set x -> init x
| Patch updates ->
List.fold_left
(fun acc -> function
| X (i, i') ->
if IntSet.mem i acc = IntSet.mem i' acc
then acc
else if IntSet.mem i acc
then IntSet.add i' (IntSet.remove i acc)
else IntSet.add i (IntSet.remove i' acc)
| R i ->
let acc = update_idx_after i (-) acc in
IntSet.remove i acc
| I (i, v) ->
let acc = update_idx_after i (+) acc in
maybe_update acc i v
| U (i, v) ->
maybe_update (IntSet.remove i acc) i v)
acc
updates
in
React.S.fold f (init (value data)) (event data)
|> React.S.map IntSet.is_empty

Error: The implementation src/reactiveData.ml
does not match the interface src/reactiveData.cmi:
...
In module RList:
Values do not match:
val for_all : ('_weak1 -> bool) -> '_weak1 t -> bool React.signal
is not included in
val for_all : ('a -> bool) -> 'a t -> bool React.signal
File "src/reactiveData.mli", line 194, characters 2-54:
Expected declaration
File "src/reactiveData.ml", line 476, characters 6-13:
Actual declaration

Steps to reproduce

Try to compile ocsigen/reactiveData#23 but with

let for_all =
let module IntSet =
Set.Make (struct type t = int let compare = Pervasives.compare end)
in
fun fn data ->

instead of

let for_all fn data =

Additional information

Delaring the IntSet module at toplevel solved the issue.

Declaring it inside the function works as well.

i.e.:
let for_all fn data =
let module IntSet =
Set.Make (struct type t = int let compare = Pervasives.compare end)
in

@vicuna

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vicuna commented Apr 20, 2018

Comment author: @Octachron

This is the intended behavior. "Set.Make(...)" is a functor application, therefore "let module M = Set.make() in fun ... -> ... " is not a value and the value restriction applies.

@vicuna vicuna closed this Apr 20, 2018

@vicuna vicuna added the typing label Mar 14, 2019

@vicuna vicuna added the bug label Mar 20, 2019

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