wrong error message in uncurried mode

[tsnobip]

I've noticed a bug in the error message that is provided when you are in uncurried mode and you provide a curried function to an uncurried signature:

module Foo: {
  let get: (Js.Dict.t<'a>, Js.Dict.key) => option<'a>
} = {
  let get = Js.Dict.get
}

this yields the following error:

[E] Line 3, column 4:

Signature mismatch:
  ...
  Values do not match:
    let get: (Js.Dict.t<'a>, Js.Dict.key) => option<'a>
  is not included in
    let get: (Js.Dict.t<'a>, Js.Dict.key) => option<'a>
  playground.res:2:3-53: Expected declaration
  playground.res:4:7-9: Actual declaration

Tested in v11.0.0-rc.3 (playground link).

Interestingly enough, it shows the correct error message when inlining the signature:

let get: (Js.Dict.t<'a>, Js.Dict.key) => option<'a> = Js.Dict.get

This function is a curried function where an uncurried function is expected

Originally got suspicious about this bug from this post on the forum.

[youngkidwarrior]

Here is another case of this issue

Compiler Error:

This function is a curried function where an uncurried function is expected

[tsnobip]

This function is a curried function where an uncurried function is expected

Hmm in this case the error message is correct, isn't it?

[youngkidwarrior]

Yeah I guess for this specific case it'd better to raise an issue in rescript relay for generating an uncurried use function

[tsnobip]

Yeah I guess for this specific case it'd better to raise an issue in rescript relay for generating an uncurried use function

it's also unclear to me why Js.Dict.get is curried, there might be another related bug.

[cristianoc]

Yeah I guess for this specific case it'd better to raise an issue in rescript relay for generating an uncurried use function

it's also unclear to me why Js.Dict.get is curried, there might be another related bug.

The compiler provides curried and uncurried versions of pervasives.
It does not do that with every library in the compiler.
The idea is to migrate to ReScript Core, which is built in uncurried mode when the project is compiled as uncurried.

[DZakh]

Related to this #6147

[DZakh]

I think that we should use the @rescript/std as an automatic dependency for rescript projects instead of getting Js_dict and etc from compiler. This way the uncurried/curried problem will be automatically solved.

Also, it'll be an improvement for packages targeting both rescript and ts only users (eg like rescript-struct). For example, now I have two options to make it work:

1. Add rescript as a peerDependency. It's fine, but in this case ts only users will need to install the whole rescript compiler, why they need a few runtime modules. It's 153mb which is not the best DX.
2. Build ts only library version with inlined rescript runtime modules. It'll be duplicated code in the bundle in case of a mixed ts/ReScript codebase.

So it can be solved by making rescript use @rescript/std. So if there's no compiler needed, only @rescript/std can be required as a peerDependency.