Re: [Caml-list] Odd type error reporting

[Leo White <leo@lpw25.net>]

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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