[SR-3550] Compound name syntax for functions with no params

Previous ID	SR-3550
Radar	None
Original Reporter	@jtbandes
Type	Improvement

Votes	0
Component/s	Compiler
Labels	Improvement, StarterProposal
Assignee	None
Priority	Medium

md5: 9e54c0bcc3910a9a4c3dc549a118933b

relates to:

• SR-1408 NSArray indexesOfObjectsPassingTest cannot be called in Swift 3

Issue Description:

The "compound name" of a function can be used to resolve ambiguities with argument labels, e.g. foo(x:) or foo(_:). However, there's no such shortcut to specify an overload that has no arguments. A workaround is to use its type with as:

import Foundation
class C: NSObject {
    func foo() {}
    func foo(x: Int) {}
}

#selector(C.foo)  // error: ambiguous use of 'foo'
#selector(C.foo(x:))  // resolve ambiguity with compound name
#selector(C.foo as (C) -> () -> ())  // resolve ambiguity by specifying type

But it'd be nice to have some way of doing this without specifying the type. Perhaps foo(_) (for symmetry with foo(_:))?