Unexported values can cause non-generalisable variables error

[vicuna]

Original bug ID: 7070
Reporter: @lpw25
Assigned to: @lpw25
Status: resolved (set by @Octachron on 2017-07-27T20:43:42Z)
Resolution: fixed
Priority: low
Severity: feature
Target version: undecided
Fixed in version: 4.06.0 +dev/beta1/beta2/rc1
Category: typing
Monitored by: @hcarty

Bug description

The following .ml file:

let r = ref []

let r = 0

gives the error message:

File "foo.ml", line 2, characters 8-14:
Error: The type of this expression, '_a list ref,
contains type variables that cannot be generalized

even though the offending value has been shadowed and so cannot cause any problems.

I think that check_nongen_scheme should probably be run on the simplified signature rather than the original signature.

[vicuna]

Comment author: @alainfrisch

Are there cases where the error you suggest to avoid is not actually related to a defect in the code (in your case, an unused declaration)?

[vicuna]

Comment author: @alainfrisch

Not sure this qualifies as a bug, so downgrading to "feature".

[vicuna]

Comment author: @lpw25

Pull request:

#1139

[vicuna]

Comment author: @Octachron

Fixed by merging the above PR.