Reason: refmt produces untypable output for exception match cases

[jberdine]

refmt on

switch (f ()) {
| x => Some x
| exception (Sys_error _ as exc) => raise exc
};

yields

switch (f ()) {
| x => Some x
| exception Sys_error _ as exc => raise exc
};

which does not type-check with Error: Unbound value exc. Warning 11 (unused match case) is also triggered.

It seems that the parens in the exception match case are required for correct parsing, but refmt removes them anyway.

[jordwalke]

Thanks, I'll get to this next.

[IwanKaramazow]

Made a pr with a fix above.

[chenglou]

Pretty good response rate we're getting =D