Re: [Caml-list] Option to fully expand types in error messages?

[Gabriel Scherer <gabriel.scherer@gmail.com>]

This does not exist to my knowledge. I think that in a bug report, it
would be interesting if you could include some reproducible code and
an example of the error messages that are not readable. I would expect
that a better solution exists, that expands enough of the paths to
clarify the error, without expanding constraints that are not related
to the type error.

One thing you might try to play with is the -short-paths options, that
tries to print shorter types (but is also possibly less predictable);
it can  expand more if that can result in showing a shorter path, so
for types that are synonyms of existing paths plus constraints it
might result in constraint expansion. (I suspect it will not solve
your problem, but that it may be of interest to other people with
unclear type error messages.)

On Thu, Jun 2, 2016 at 3:18 PM, Carette, Jacques <carette@mcmaster.ca> wrote:
> In writing some code which uses a lot of monads with underlying types which
> use constraints, even simple errors can lead to extremely hard to read error
> messages.  The main reason is that the two types given in errors are
> partially expanded, to different levels.  This frequently means that the
> part where the type checker detects a mismatch is (extremely) opaque to
> human eyes.
>
> In that case, it would actually be preferable to fully expand the types.
> Yes, that will produce wallpaper.  But at least the mismatch should be
> considerably easier to catch.
>
> Does this already exist, or should I submit a feature request?
>
> Jacques