[swift-evolution] [Discussion] Parentheses

[Anton Zhilin]

> Or maybe I have just forgotten the reasons for why there can be no such
thing as (a nested) single element tuple (type).

In Swift, types have their own (built-in) operators: infix '->', postfix
'?', postfix '!'.
Parentheses are required for grouping (setting priorities). If we allow
single element tuples, ambiguities arise:

(Int -> Int)?  // is that an optional tuple or just optional function?

By the way, in Haskell, which allows user-defined operators on types, there
is no single element tuple for pretty much the same reason.
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