Open Radar

 
Summary:
Dear Swift team,
I hope this radar finds you well ❤️


See rdar://19235463 for context re: tuple types. All of that applies to function arguments, quite directly, but also to returns, in two senses:

1. When returning a tuple type—again, this is basically the tuple case so I won’t address it in this radar.
2. When using curried functions, e.g. T -> U -> V

You can see this by writing curry/uncurry functions. Curry can’t be defined over an arbitrary number of arguments, and uncurry can’t be defined over a arbitrary number of returns. So you get to write binary curry; ternary curry; quaternary curry; etc.

The splat syntax might apply nicely for curried function types:

	T -> *U // “*U” meaning “splat the returns of U”

But that might also be ambiguous (whether to the compiler or to the reader/writer) with T -> (*U) which has a definition under the previous radar. I used up all of my reserves of creativity in the last radar so I’m afraid you’re on your own here :)

I could see this being a more marginal use case, but it would be helpful in my framework Prelude[1] where I have implemented curry/uncurry for binary and ternary functions[2] and will probably implement them for quaternary functions sooner or later because that’s just the sort of thing I do.


Steps to Reproduce:
N/A

Expected Results:
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Actual Results:
N/A

Regression:
N/A

Notes:
1: https://github.com/robrix/Prelude
2: https://github.com/robrix/Prelude/blob/master/Prelude/Curry.swift