Original bug ID: 1274
Reporter: administrator
Status: closed
Resolution: fixed
Priority: normal
Severity: minor
Category: ~DO NOT USE (was: OCaml general)

Bug description

Full_Name: John Prevost
Version: 3.05
OS: Windows
Submission from: 208.167.88.80 (208.167.88.80)

I've discovered a fairly serious typechecking bug in 3.05. I'm
also mentioning it on the mailing list so that people are aware.

You can do the following:

type bad = { x : 'a . 'a option ref };;

type bad = { x : 'a. 'a option ref; }

let bv = { x = ref None };;

val bv : bad = {x = {contents = None}}

bv.x := Some 5;;

• : unit = ()

let extra_bad = !(bv.x);;

val extra_bad : '_a option = Some

f extra_bad;;

CRASH

It looks like mutable fields are handled correctly and catch that the
value is not, in fact, general enough. But when the mutable field is
part of the value (in this case, part of the ref), the check is not
done.