[swift-evolution] [pitch] Eliminate the "T1 -> T2" syntax, require "(T1) -> T2"

[Антон Жилин]

>
> Therefore the impermissible:
> (()) -> () Is identical to:
> (Void) -> () So to follow these rules, it must instead be:
> Void -> () … and we’re back to T1 -> T2 :* )*


Wrong! If we enforce parentheses in function types, we won't be able to write

Void -> ()

Parentheses will be required on the grammar level. The correct way to
write this will be:

() -> ()  or  () -> Void

The following will be legal:

(Void) -> ()  and  (()) -> ()

It is a function that takes a single parameter () and returns ().

I additionally propose that the following should be illegal, because
additional parentheses aren't needed there:

((())) -> ()  and  () -> (())  and just (Int) and (())

Hope it cleared up things a little bit.

- Anton
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