Reason: [refmt] Add newline before each type alternative

[kassens]

I think the formatter should add newlines before the | in type definitions.

/* input and desired(?) output */
type binTree 'x =
  | Node of (binTree 'x) (binTree 'x)
  | Leaf of 'x;

/* current refmt output */
type binTree 'x = | Node of (binTree 'x) (binTree 'x) | Leaf of 'x;

[chenglou]

It will add the newlines once it sees that the variant exceeds the width limit.

[jordwalke]

Jan, do you think it should always break lines? This would be super easy to do (see reason_pprint_ast.ml). Feel free to take a stab at it (tagging as good first task).

[chenglou]

Btw I'm totally fine with it being on a single line; But if we keep that, removing the first | would be nice

[kassens]

I think for multiple alternatives(?) it seems like they're more readable on multiple lines, see the example on top. For really simple types you could make a case to put them on one line, like:

type decision = Yes | No | Maybe;

I might be more on the side of using more lines even if they technically fit on one line.

[jordwalke]

We cannot easily include a leading bar only if it breaks into multiple lines. You could send a pull request so that it always breaks when there is more than one variant leaf and only if needed when there is exactly one variant leaf.

[yunxing]

I think it is ok to always break lines like:

type decision = 
   | Yes 
   | No
   | Maybe;

[kassens]

I'll give it a shot.

[jberdine]

Another position on this: if the type definition is short enough to fit on one line and not self-evident enough, add comments, then it won't fit on one line anymore. :-)

[kassens]

Is there a difference between

type x = A;

and

type X = | A;