Surround operators with parens when pretty-printing

[brendanzab]

For example:

> { (+) = \x y -> "squiggly squiggle" }
<top>:Line: 1, Column: 1: Expected the following types to be equal
Expected: { +: 1476 -> 1477 -> String }
Found: { ord: std.prelude.Ord 1479, +: 1479 -> 1479 -> 1479, -: 1479 -> 1479 -> 1479, *: 1479 -> 1479 -> 1479, /: 1479 -> 1479 -> 1479, negate: 1479 -> 1479 }
1 errors were found during unification:
Types do not match:
    Expected: { +: 1476 -> 1477 -> String }
    Found: { ord: std.prelude.Ord 1479, +: 1479 -> 1479 -> 1479, -: 1479 -> 1479 -> 1479, *: 1479 -> 1479 -> 1479, /: 1479 -> 1479 -> 1479, negate: 1479 -> 1479 }
{ (+) = \x y -> "squiggly squiggle" }
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[brendanzab]

I'm wondering how we might recover the fact that a function (or type?) should be treated as an operator... should we base it off the characters contained in the identifier, or would it be worth storing a flag somewhere?

[Marwes]

There should be function in the lexer.rs which determines if a character is an operator or not. Should be fine to just use that on the first character.