Vincent Hanquez wrote:

On Wed, May 23, 2007 at 09:16:44AM +1000, skaller wrote:

On Tue, 2007-05-22 at 18:10 -0400, David Teller wrote:

* Error messages of the type system are somewhat obscure. The reflex of
many students is "OCaml wants it to be of type XXX", rather than "there
is a contradiction in what I wrote". It would be nice if there was a way
to ask OCaml to display additional information on type errors.

This is a long standing peeve of mine. Lets face it: Ocaml just lies.
If it has inferred a type, then finds a contradiction, it should
report both the location of the contradication AND all of the source
lines that contributed to the inference.


I agree, this is one of the worst thing about ocaml type inference,
and you sometimes end up to have to put explicit type to functions to
find the offending lines (usually hundreds lines before the actual line
that's printed), defeating the whole thing...

Cheers,

Hundreds of lines? I've seen ten's of lines, but never hundreds.

Of course, I generally type annotate at the level of functions at least (using .mli files is to be encouraged, IMO). So type errors generally don't escape functions. And I keep functions reasonably short- tens of lines long at most...

Brian