Support @new @variadic

[cannorin]

Closes #5363.

This PR allows @new and @variadic to be used simultaneously.

'use strict';
class Foo {
    constructor(...names) {
        this.names = names;
    }
}
let foo = new Foo("bar", "baz");
console.log(foo.names);

type foo
@get external names: foo => array<string> = "names"
@new @variadic external makeFoo : array<string> => foo = "Foo"
let foo = makeFoo(["bar", "baz"])
Js.log(foo->names)

[bobzhang]

Would @raw cover your use case?
We would like to have diffs small for easy review

[cannorin]

Would @raw cover your use case?

%raw can't easily workaround this when the class is imported.

Also, it's kind of unnatural for me (and perhaps for many other users) that @new @variadic does not work. Docs also doesn't mention they don't work when used together.

We would like to have diffs small for easy review

"small diffs" means no changes to jscomp/main/builtin_cm*_datasets.ml and lib/**/*, right?

[bobzhang]

"small diffs" means no changes to jscomp/main/builtin_cm*_datasets.ml and lib/**/*, right?

Yes, ideally no white space changes or in a separate commit.

[cannorin]

@bobzhang done 👍

[cannorin]

No pressure, but it would be great if this gets included in v10.0.

I continue to be available for resolving any reviews and change requests in the foreseeable future.

[cristianoc]

@cannorin happy to take a look, but unsure what aspect should be checked.
Anything that one should focus on? That existing features are not affected? That all cases are covered? Code style? Others?

[cannorin]

@cristianoc thank you!

Since the PR is about modifying @new so that it allows @splice to be used together, the main concerns would be:

• the existing @new codes would not break
• the coding style

[cristianoc]

OK I'll have a go. Might ask some basic question about the codebase.
Meanwhile: CI looks red.

[cristianoc]

Also, the changelog should be updated.

[cannorin]

Thanks! I will work on changelog and CI tomorrow.

[cannorin]

applied the reviews 🚀

[cannorin]

Error: Conflicting attributes: Attribute found that conflicts with %@new

hmm, it seems that the modified compiler is not used during CI run?

I didn't stage the following files. Do I need to check in these files to make CI use the modified compiler?

        modified:   jscomp/main/builtin_cmi_datasets.ml
        modified:   jscomp/main/builtin_cmj_datasets.ml
        modified:   jscomp/test/splice_test.js
        modified:   lib/4.06.1/unstable/js_compiler.ml
        modified:   lib/4.06.1/unstable/js_playground_compiler.ml
        modified:   lib/4.06.1/whole_compiler.ml
        modified:   lib/es6/caml_splice_call.js
        modified:   lib/js/caml_splice_call.js

[cannorin]

I try to stage everything in a separate commit (so that it can be easily reverted) and see what happens

[cannorin]

macos-arm didn't run but everything else is now green 🚀

[cristianoc]

Sometimes macOS-arm needs a bit of encouragement.
Good to go. Ready to merge if there's nothing outstanding.