Ligature from rust unit type () to empty set ∅

[lgarczyn]

Ideally should only happen after a comma, open parenthesis or space, or never after an alphanumerical character:

foo();
foo(∅);
foo(bar, ∅);
∅

Other rust ligatures could be

&[
r#" foobar "

[cblp]

1. Unit is not an empty set, it is a 1-element set.
2. Conflict with Data.Monoid.Unicode.∅

[cblp]

3. This is not a ligature, () can't be drawn as ∅, (/) may be, but not ()

[alexlucas309]

This seems like it would just look confusing. Plus, it's not an accurate representation of the type.

[yvvt0379]

@lgarczyn I don't think so. Imho, this will only add to confusion.