Bug: AST diff around pcd_vars

[alanechang]

The example program:

type _ g = MkG : 'a . 'a g;;

gets formatted into:

type _ g = MkG : 'a g

producing unequal ASTs:

19d18
<                   pcd_vars = 'a

fmt_constructor_arguments_result in Fmt_ast is the relevant function here. Wonder if we should keep 'a . or opt to add some additional normalization logic.

[Julow]

Thanks for the report! This should be fixed by #2518

This is a quick and dirty fix, though. Ideally, we'd separate the code that recognize what form of constructor we're formatting and the code that formats it.
This is usually done in the Sugar module. Contribution welcome :)