swift-mirror/test/Constraints/subscript.swift

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

// Simple subscript of arrays:
func simpleSubscript(_ array: [Float], x: Int) -> Float {
  _ = array[x]
  return array[x]
}

// Subscript of archetype.
protocol IntToStringSubscript {
  subscript (i : Int) -> String { get }
}

class FauxDictionary {
  subscript (i : Int) -> String {
    get {
      return String(i)
    }
  }
}

func archetypeSubscript<T : IntToStringSubscript, U : FauxDictionary>(_ t: T, u: U)
       -> String {
  // Subscript an archetype.
  if false { return t[17] }

  // Subscript an archetype for which the subscript operator is in a base class.
  return u[17]
}

// Subscript of existential type.
func existentialSubscript(_ a: IntToStringSubscript) -> String {
  return a[17]
}

// Static of above:

// Subscript of archetype.
protocol IntToStringStaticSubscript {
  static subscript (i : Int) -> String { get }
}

class FauxStaticDictionary {
  static subscript (i : Int) -> String {
    get {
      return String(i)
    }
  }
}

func archetypeStaticSubscript<
  T : IntToStringStaticSubscript, U : FauxStaticDictionary
>(_ t: T.Type, u: U.Type) -> String {
  // Subscript an archetype.
  if false { return t[17] }
  
  // Subscript an archetype for which the subscript operator is in a base class.
  return u[17]
}

// Subscript of existential type.
func existentialStaticSubscript(
  _ a: IntToStringStaticSubscript.Type
) -> String {
  return a[17]
}


class MyDictionary<Key, Value> {
  subscript (key : Key) -> Value {
    get {}
  }
}

class MyStringToInt<T> : MyDictionary<String, Int> { }

// Subscript of generic type.
func genericSubscript<T>(_ t: T,
                         array: Array<Int>,
                         i2i: MyDictionary<Int, Int>,
                         t2i: MyDictionary<T, Int>,
                         s2i: MyStringToInt<()>) -> Int {
  if true { return array[5] }
  if true { return i2i[5] }
  if true { return t2i[t] }
  return s2i["hello"]
}



// <rdar://problem/21364448> QoI: Poor error message for ambiguous subscript call
extension String {
  func number() -> Int {  }     // expected-note {{found candidate with type '() -> Int'}}
  func number() -> Double {  }  // expected-note {{found candidate with type '() -> Double'}}
}

let _ = "a".number  // expected-error {{ambiguous use of 'number()'}}

extension Int {
  subscript(key: String) -> Int { get {} }      // expected-note {{found candidate with type '(String) -> Int'}}
  subscript(key: String) -> Double {  get {} }   // expected-note {{found candidate with type '(String) -> Double'}}
}

let _ = 1["1"]  // expected-error {{ambiguous use of 'subscript(_:)'}}

let squares = [ 1, 2, 3 ].reduce([:]) { (dict, n) in
  var dict = dict
  dict[n] = n * n
  return dict
}

// <rdar://problem/23670252> QoI: Misleading error message when assigning a value from [String : AnyObject]
func r23670252(_ dictionary: [String : AnyObject], someObject: AnyObject) {
  let color : String?
  color = dictionary["color"]  // expected-error {{cannot assign value of type 'AnyObject?' to type 'String?'}}
  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('AnyObject' and 'String') are expected to be equal}}
  _ = color
}


// https://github.com/apple/swift/issues/43333
// Type mismatch reported as extraneous parameter
do {
  struct S {
    subscript(b : Int) -> Int
      { return 0 }
    subscript(a a : UInt) -> Int { return 0 }
  }

  S()[a: Int()] // expected-error {{cannot convert value of type 'Int' to expected argument type 'UInt'}}
}

// rdar://problem/25601561 - Qol: Bad diagnostic for failed assignment from Any to more specific type

struct S_r25601561 {
  func value() -> Any? { return "hi" }
}

class C_r25601561 {
  var a: [S_r25601561?] = []
  func test(i: Int) -> String {
    let s: String = a[i]!.value()! // expected-error {{cannot convert value of type 'Any' to specified type 'String'}}
    return s
  }
}

// rdar://problem/31977679 - Misleading diagnostics when using subscript with incorrect argument

func r31977679_1(_ properties: [String: String]) -> Any? {
  return properties[0] // expected-error {{cannot convert value of type 'Int' to expected argument type 'String'}}
}

func r31977679_2(_ properties: [String: String]) -> Any? {
  return properties["foo"] // Ok
}

// rdar://problem/45819956 - inout-to-pointer in a subscript arg could use a better diagnostic
func rdar_45819956() {
  struct S {
    subscript(takesPtr ptr: UnsafeMutablePointer<Int>) -> Int {
      get { return 0 }
    }
  }

  let s = S()
  var i = 0

  // TODO: It should be possible to suggest `withUnsafe[Mutable]Pointer` as a fix-it
  _ = s[takesPtr: &i]
  // expected-error@-1 {{cannot pass an inout argument to a subscript; use 'withUnsafeMutablePointer' to explicitly convert argument to a pointer}}
}

// rdar://problem/45825806
// https://github.com/apple/swift/issues/49738
// Array-to-pointer in subscript arg crashes compiler
do {
  struct S {
    subscript(takesPtr ptr: UnsafePointer<Int>) -> Int {
      get { return 0 }
    }
  }

  let s = S()
  _ = s[takesPtr: [1, 2, 3]] // Ok
}

func test_generic_subscript_requirements_mismatch_diagnostics() {
  struct S {
    subscript<T: StringProtocol>(_: T) -> T { // expected-note {{where 'T' = 'Int'}}
      fatalError()
    }

    subscript<T, U: Collection>(v v: [T]) -> U where U.Element == T {
      fatalError()
    }

    subscript<T: Collection>(number num: T) -> Int where T.Element: BinaryInteger {
      // expected-note@-1 {{'T.Element' = 'String'}}
      return 42
    }
  }

  var s = S()
  _ = s[42] // expected-error {{subscript 'subscript(_:)' requires that 'Int' conform to 'StringProtocol'}}

  var arr: [Int] = []
  let _: [String] = s[v: arr] // expected-error {{cannot convert value of type '[Int]' to expected argument type '[String]'}}
  // expected-note@-1 {{arguments to generic parameter 'Element' ('Int' and 'String') are expected to be equal}}

  s[number: ["hello"]] // expected-error {{subscript 'subscript(number:)' requires that 'String' conform to 'BinaryInteger'}}
}

// rdar://61084565 - infinite recursion in dynamic member lookup
func rdar61084565() {
  @dynamicMemberLookup
  struct Foo {
    subscript(dynamicMember _: KeyPath<Foo, Int>) -> Int {
      return 42
    }
  }

  let a = Foo()
  a[] // expected-error {{value of type 'Foo' has no subscripts}}
}

// Note: In Swift >= 6 mode this would become an error.
func test_subscript_accepts_type_name_argument() {
  struct A {
    subscript(a: A.Type) -> Int { get { 42 } }
  }

  func test(a: A, optA: A?) {
    let _ = a[A] // expected-warning {{expected member name or initializer call after type name; this will be an error in Swift 6}}
    // expected-note@-1 {{add arguments after the type to construct a value of the type}} {{16-16=()}}
    // expected-note@-2 {{use '.self' to reference the type object}} {{16-16=.self}}

    let _ = optA?[A] // expected-warning {{expected member name or initializer call after type name; this will be an error in Swift 6}}
    // expected-note@-1 {{add arguments after the type to construct a value of the type}} {{20-20=()}}
    // expected-note@-2 {{use '.self' to reference the type object}} {{20-20=.self}}
  }
}