Re: [Caml-list] Improved type error messages for Ocaml

["Arthur Charguéraud" <arthur.chargueraud@inria.fr>]

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Hi Ivan,

Thanks for your feedback.

# print_int 2+2;;

I don't like the idea of testing whether the term would type-check with 
a different parenthesization. First of all, it might be expensive or 
complex to test. Second, it may lead to suggestions that are even more 
confusing.

One proposal that I would like better to handle your scenario is the 
following: if an infix binary operator (other than ';') has a first 
argument of type unit, then suggest that parentheses might be missing.

I can try to implement that, unless someone argues against this proposal.

Thanks,
+
Arthur

> Impressive!
>
> By the way, one of the most common mistakes is to forget that a 
> function application binds tighter than
> infix operators, e.g.,
>
>
>  # print_int 2+2;;
>
> Although your branch already provides a nice error message:
>
>     Error: The function `+' cannot be applied to the arguments provided.
>
>        | Types of the expected arguments:    | Types of the provided
>     arguments:
>     ---|-------------------------------------|------------------------------------
>      1 | int                     | unit
>      2 | int                     | int
>
>
> that is probably better than the default:
>
>     Error: This expression has type unit but an expression was
>     expected of type
>              int
>
> it is still probably a good idea, to provide an ad-hoc error message 
> here (as you did for missing `()`, `!` and `rec`).
>
> In this case, if an offending expression contains a binary operator 
> which has an application to the left and some simpl_expr
> on the right, and if we can fix it by parenthesizing the expression, 
> then we can suggest adding parentheses around the expression.
>
> Regards,
> Ivan Gotovchits
>
> On Thu, Jan 12, 2017 at 4:37 PM, SP <sp@orbitalfox.com 
> <mailto:sp@orbitalfox.com>> wrote:
>
>     Nice!
>
>     --
>         SP
>
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