Re: [Caml-list] Odd type error reporting

[octachron <octa@polychoron.fr>]

The mantis ticket might be this one:

http://caml.inria.fr/mantis/view.php?id=6931

Regards,
octachron.

Le 06/15/16 à 10:52, Leo White a écrit :
> This bug was fixed in 4.03.0:
>
>    Characters 29-32:
>    let () = { f = fun bar -> { bar } };;
>                                ^^^
> Error: This record expression is expected to have type foo
>         The field bar does not belong to type foo
>
> I vaguely remember a mantis about this (or a similar issue) and that
> it was resolved, but I don't have its PR number to hand.
>
> Regards,
>
> Leo
>
> On Wed, 15 Jun 2016, at 03:37 AM, Christoph Höger wrote:
>> Dear all,
>>
>> It just took me 30min to figure out a rather simple type-error in my
>> code. It was complicated by ocamlc's strange error reporting. Consider
>> this example:
>>
>> % cat error.ml
>> type foo = { foo : int }
>> type bar = { bar : int }
>> type baz = { f : int -> foo }
>>
>> let () = { f = fun bar -> { bar } }
>> % ocamlc error.ml
>> File "error.ml", line 5, characters 28-31:
>> Error: This record expression is expected to have type baz
>>         The field bar does not belong to type foo
>>
>>
>>
>> ocamlc correctly spots the "bar" in the last line as the source of the
>> error. However, it says, it is expected to have type "baz", but that is
>> the surrounding constructor.
>>
>> In fact, the "correct" error is:
>>
>> File "error.ml", line 5, characters 26-33:
>> Error: This record expression is expected to have type foo
>>         The field bar does not belong to type foo
>>
>>
>>
>> Obviously, in a perfect world, the wrongly labeled field should be
>> pointed out as well (kind of a sub-error). However, it seems problematic
>> that the outermost record-mismatch is reported.
>>
>> Is this a known bug/feature? Does it change in later versions (I am on
>> 4.02.3 now)?
>>
>> thanks,
>>
>> Christoph
>> -- 
>> Christoph Höger
>>
>> Technische Universität Berlin
>> Fakultät IV - Elektrotechnik und Informatik
>> Übersetzerbau und Programmiersprachen
>>
>> Sekr. TEL12-2, Ernst-Reuter-Platz 7, 10587 Berlin
>>
>> Tel.: +49 (30) 314-24890
>> E-Mail: christoph.hoeger@tu-berlin.de
>>
>> -- 
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