Issue Description:

Hello,

The Swift 5.5 compiler won't accept the shorthand notation .staticMember for existential values, as described by SE-0299 Extending Static Member Lookup in Generic Contexts, when there exist an overload that accepts another input.

I stumbled upon this issue while trying to enhance an API that provides both a method that accepts a variadic input, as well as an array, as a convenience. The overloads prevents the user from using the shorthand notation, ruining SE-0299 benefits.

See in the sample code below four examples, two successes, and two unexpected compiler errors:

// ======
// SE-0299 setup

protocol P { }
struct S: P { }
extension P where Self == S {
    static var s: Self { S() }
}

// ======
// SE-0299 successes

func f1(_ p: P) { }
f1(.s) // OK

func f2(_ ps: P...) { }
f2(.s) // OK

// ======
// SE-0299 failures

func f3(_ ps: P...) { }
func f3(_ ps: [P]) { }
f3(.s) // error: Type '[P]' has no member 's'

func f4(_ p: P) { }
func f4(_ int: Int) { }
f4(.s) // error: Type 'Int' has no member 's'