[Syntax] Convert poly variant from using ` to #

[chenglou]

This is a stepping stone to turning interpolated string from {|bla|} to
bla. Which is more familiar to JS devs and frees the weird syntax
error of switch bla {|lol => 1}

Test plan: make test

[yunxing]

Looks good to me, feel free to merge.

[jordwalke]

I'm pretty sure this breaks something somewhere.

obj #x

Is that an obj function that you're passing the #x variant to, or is obj an object?

[jordwalke]

Aside from getting this to work with objects, there's a couple of other things:
0. Objects (as I mentioned). We could use this syntax for method calls instead (myObject.myMethod:: arg)

1. There's a bunch of rules around precedence for sharp. We need to ensure we didn't cause bugs there.
2. Sharp is used other places (one place that might cause issues.).

[SanderSpies]

Has there been any consensus yet on how the # will be used? @chenglou asked me to look into this, but I want to make sure it's still on the table to be implemented.

Also if we do want to have this, where can I best start with writing tests?

[hhugo]

How does the following convert to Reason ?

type t = [ `a | `b ]
type u = [ t | `c ]
let f = function
  | #t -> 1
  | `c -> 2

[SanderSpies]

On my machine it converts to:

type t = [ | `a | `b];
type u = [ t | `c];

let f =
  fun
  | #t => 1
  | `c => 2;

I don't think we have tests for this yet - at least a quick search for # within formatTests didn't show this scenario.

[hhugo]

@SanderSpies, this doesn't reflect this very PR (which is marked as merged).

[SanderSpies]

@hhugo It was reverted.

[hhugo]

got it.

[braibant]

Regarding switch bla {|lol => 1}, how do you plan to support the identifiers part of quoted/interpolated strings in reason? http://caml.inria.fr/pub/docs/manual-ocaml/extn.html#sec249

This makes it possible to have an arbitrary number of string litteral delimiters (which is nice when nesting those interpolated strings), and there was plans to use those identifiers in PPX rewriters IIRC.

[chenglou]

JS has the syntax blastuff. Maybe we can use that

[braibant]

Can you give an example of how this works?

[braibant]

Note that int_of_string"1" works in OCaml, and I do not see how this would go with the backtick proposal.

[hcarty]

How would

{foo|foo`|foo}

translate, as a concrete example?