I am currently working on #3384, with the intent of ensuring that parse (ppr (parse source)) == parse source I have hit the issue where foo :: (Int) has the parens reflected in the original parsed AST, but the types pretty printer goes to a lot of trouble to remove any parens not required to interpret the meaning of the type. So the question is, should the default ppr faithfully reproduce the source that was parsed to generate the given AST, or simplify it?
From a round-tripping perspective I prefer the former, but there are other use cases where the current behaviour is preferred.
If the original is preferred, it can perhaps be enabled via a flag to the pretty printer, but before doing that I want to see if it actually matters. Alan