Idea: Remove unnecessary parentheses around simple constructs

[lydell]

When refactoring code it is easy to end up with some unnecessary parentheses:

-Workflow.run (makeRequest author) "/invoices"
+Workflow.run (makeRequest) "/invoices"

It would be nice if Fantomas could automatically remove the now unnecessary parentheses above!

I’m thinking that parentheses could be removed in the following cases:

• Around an identifier: (x) → x
• Around a literal: (5) → 5, ("x") → "x"
• Double parens: ((whatever foo)) → (whatever foo)
• Around a “top expression”: let x = (whatever foo) → let x = whatever foo, | Some x -> (Ok x) → | Some x -> Ok x
• Maybe other cases as well that you can think of! For me, it does not have to be comprehensive – it would be helpful if at least a few of the most common cases was supported.

[nojaf]

I'm very skeptical of this proposal. This seems more like a thing for analyzer instead of a code formatter.
I'm not entirely sure Fantomas can make the correct assumptions of removing ( with the guarantee that the code will still compile.

[lydell]

For more context, I’m used to this behavior from Prettier and elm-format 🤷‍♂

[nojaf]

Yes, and to be clear I agree that is is nice behavior. My main concern is that we are introducing something that could break people's code. At first glance it might not be that easy to implement.

I would like to see a proof of concept PR to measure the impact in the code base.