swift-mirror/test/Sema/call_as_function_generic.swift

// RUN: %target-typecheck-verify-swift

protocol P0 {
  func callAsFunction(x: Self)
}

struct ConcreteType {
  func callAsFunction<T, U>(_ x: T, _ y: U) -> (T, U) {
    return (x, y)
  }

  func callAsFunction<T, U>(_ fn: @escaping (T) -> U) -> (T) -> U {
    return fn
  }
}

let concrete = ConcreteType()
_ = concrete(1, 3.0)
_ = concrete(concrete, concrete.callAsFunction as ([Int], Float) -> ([Int], Float))

func generic<T, U>(_ x: T, _ y: U) {
  _ = concrete(x, x)
  _ = concrete(x, y)
}

struct GenericType<T : Collection> {
  let collection: T
  func callAsFunction<U>(_ x: U) -> Bool where U == T.Element, U : Equatable {
    return collection.contains(x)
  }
}

// Test conditional conformance.
extension GenericType where T.Element : Numeric {
  func callAsFunction(initialValue: T.Element) -> T.Element {
    return collection.reduce(initialValue, +)
  }
}

let genericString = GenericType<[String]>(collection: ["Hello", "world", "!"])
_ = genericString("Hello")
let genericInt = GenericType<Set<Int>>(collection: [1, 2, 3])
_ = genericInt(initialValue: 1)

// https://github.com/apple/swift/issues/53787

class C<T> {}
protocol P1 {}
extension C where T : P1 { // expected-note {{where 'T' = 'Int'}}
  func callAsFunction(t: T) {}
}

struct S0 : P1 {}

func testCallAsFunctionWithWhereClause(_ c1: C<Int>, _ c2: C<S0>, _ s0: S0) {
  c1(42) // expected-error {{referencing instance method 'callAsFunction(t:)' on 'C' requires that 'Int' conform to 'P1'}}
  // expected-error@-1 {{missing argument label 't:' in call}}

  c2(t: s0) // Okay.
}