Use conditional conformances to implement Equatable for Optional, Array, and Dictionary

CHANGELOG.md

@@ -22,6 +22,13 @@ CHANGELOG
 Swift 4.1
 ---------
 
+* [SE-0143][] The standard library types `Optional`, `Array`, and
+	`Dictionary` now conform to the `Equatable` protocol when their element types
+	conform to `Equatable`. This allows the `==` operator to compose (e.g., one
+	can compare two values of type `[Int : [Int?]?]` with `==`), as well as use
+  various algorthims defined for `Equatable` element types, such as
+	`index(of:)`.
+
 * [SE-0157][] is implemented. Associated types can now declare "recursive"
 	constraints, which require that the associated type conform to the enclosing
 	protocol. The standard library protocols have been updated to make use of

stdlib/public/core/Arrays.swift.gyb

@@ -2187,7 +2187,7 @@ extension _ArrayBufferProtocol {
 
 % for (Self, a_Self) in arrayTypes:
 
-extension ${Self} where Element : Equatable {
+extension ${Self} : Equatable where Element : Equatable {
   /// Returns `true` if these arrays contain the same elements.
   @_inlineable
   public static func ==(lhs: ${Self}<Element>, rhs: ${Self}<Element>) -> Bool {

stdlib/public/core/HashedCollections.swift.gyb

@@ -2709,7 +2709,7 @@ extension Dictionary {
   }
 }
 
-extension Dictionary where Value : Equatable {
+extension Dictionary : Equatable where Value : Equatable {
   @_inlineable // FIXME(sil-serialize-all)
   public static func == (lhs: [Key : Value], rhs: [Key : Value]) -> Bool {
     switch (lhs._variantBuffer, rhs._variantBuffer) {

stdlib/public/core/Optional.swift

@@ -313,7 +313,7 @@ func _diagnoseUnexpectedNilOptional(_filenameStart: Builtin.RawPointer,
     line: UInt(_line))
 }
 
-extension Optional where Wrapped : Equatable {
+extension Optional : Equatable where Wrapped : Equatable {
   /// Returns a Boolean value indicating whether two optional instances are
   /// equal.
   ///

test/Constraints/bridging.swift

@@ -181,8 +181,10 @@ func dictionaryToNSDictionary() {
 struct NotEquatable {}
 func notEquatableError(_ d: Dictionary<Int, NotEquatable>) -> Bool {
   // FIXME: Another awful diagnostic.
-  return d == d // expected-error{{binary operator '==' cannot be applied to two 'Dictionary<Int, NotEquatable>' operands}}
-  // expected-note @-1 {{overloads for '==' exist with these partially matching parameter lists: }}
+  return d == d // expected-error{{'<Self where Self : Equatable> (Self.Type) -> (Self, Self) -> Bool' requires that 'NotEquatable' conform to 'Equatable'}}
+  // expected-note @-1 {{requirement from conditional conformance of 'Dictionary<Int, NotEquatable>' to 'Equatable'}}
+  // expected-error @-2 {{type 'NotEquatable' does not conform to protocol 'Equatable'}}
+  // expected-note @-3{{requirement specified as 'NotEquatable' : 'Equatable'}}
 }
 
 // NSString -> String

test/Constraints/patterns.swift

@@ -163,9 +163,8 @@ case nil?: break // expected-warning {{case is already handled by previous patte
 default: break
 }
 
-// <rdar://problem/21995744> QoI: Binary operator '~=' cannot be applied to operands of type 'String' and 'String?'
 switch ("foo" as String?) {
-case "what": break // expected-error{{expression pattern of type 'String' cannot match values of type 'String?'}} {{12-12=?}}
+case "what": break
 default: break
 }
 

test/Parse/enum.swift

@@ -144,7 +144,7 @@ enum RawTypeNotFirst : RawTypeNotFirstProtocol, Int { // expected-error {{raw ty
 }
 
 enum ExpressibleByRawTypeNotLiteral : Array<Int> { // expected-error {{raw type 'Array<Int>' is not expressible by any literal}}
-  // expected-error@-1{{'ExpressibleByRawTypeNotLiteral' declares raw type 'Array<Int>', but does not conform to RawRepresentable and conformance could not be synthesized}} expected-error@-1 {{RawRepresentable conformance cannot be synthesized because raw type 'Array<Int>' is not Equatable}}
+  // expected-error@-1{{'ExpressibleByRawTypeNotLiteral' declares raw type 'Array<Int>', but does not conform to RawRepresentable and conformance could not be synthesized}}
   case Ladd, Elliott, Sixteenth, Harrison
 }
 

test/Parse/pointer_conversion.swift.gyb

@@ -291,8 +291,10 @@ struct NotEquatable {}
 func arrayComparison(_ x: [NotEquatable], y: [NotEquatable], p: UnsafeMutablePointer<NotEquatable>) {
   var x = x
   // Don't allow implicit array-to-pointer conversions in operators.
-  let a: Bool = x == y // expected-error{{binary operator '==' cannot be applied to two '[NotEquatable]' operands}}
-  // expected-note @-1 {{overloads for '==' exist with these partially matching parameter lists:}}
+  let a: Bool = x == y // expected-error{{'<Self where Self : Equatable> (Self.Type) -> (Self, Self) -> Bool' requires that 'NotEquatable' conform to 'Equatable'}}
+  // expected-error @-1 {{type 'NotEquatable' does not conform to protocol 'Equatable'}}
+  // expected-note @-2 {{requirement from conditional conformance of '[NotEquatable]' to 'Equatable'}}
+  // expected-note @-3 {{requirement specified as 'NotEquatable' : 'Equatable'}}
 
   let _: Bool = p == &x  // Allowed!
 }

test/Sema/enum_equatable_conditional.swift

@@ -1,8 +1,5 @@
 // RUN: %target-typecheck-verify-swift
 
-// FIXME: Should be part of the standard library.
-extension Array: Equatable where Element: Equatable { }
-
 struct NotEquatable { }
 
 enum WithArrayOfNotEquatables : Equatable { // expected-error{{type 'WithArrayOfNotEquatables' does not conform to protocol 'Equatable'}}

test/Sema/enum_equatable_hashable.swift

@@ -35,7 +35,7 @@ enum CustomHashable {
 
   var hashValue: Int { return 0 }
 }
-func ==(x: CustomHashable, y: CustomHashable) -> Bool { // expected-note 3 {{non-matching type}}
+func ==(x: CustomHashable, y: CustomHashable) -> Bool { // expected-note 4 {{non-matching type}}
   return true
 }
 
@@ -50,7 +50,7 @@ enum InvalidCustomHashable {
 
   var hashValue: String { return "" } // expected-note{{previously declared here}}
 }
-func ==(x: InvalidCustomHashable, y: InvalidCustomHashable) -> String { // expected-note 3 {{non-matching type}}
+func ==(x: InvalidCustomHashable, y: InvalidCustomHashable) -> String { // expected-note 4 {{non-matching type}}
   return ""
 }
 if InvalidCustomHashable.A == .B { }
@@ -172,7 +172,7 @@ public enum Medicine {
 
 extension Medicine : Equatable {}
 
-public func ==(lhs: Medicine, rhs: Medicine) -> Bool { // expected-note 2 {{non-matching type}}
+public func ==(lhs: Medicine, rhs: Medicine) -> Bool { // expected-note 3 {{non-matching type}}
   return true
 }
 
@@ -189,7 +189,7 @@ extension NotExplicitlyHashableAndCannotDerive : Hashable {} // expected-error 2
 // Verify that conformance (albeit manually implemented) can still be added to
 // a type in a different file.
 extension OtherFileNonconforming: Hashable {
-  static func ==(lhs: OtherFileNonconforming, rhs: OtherFileNonconforming) -> Bool { // expected-note 2 {{non-matching type}}
+  static func ==(lhs: OtherFileNonconforming, rhs: OtherFileNonconforming) -> Bool { // expected-note 3 {{non-matching type}}
     return true
   }
   var hashValue: Int { return 0 }
@@ -226,6 +226,17 @@ indirect enum TotallyIndirect: Hashable {
   case end(Int)
 }
 
+// Check the use of conditional conformances.
+enum ArrayOfEquatables : Equatable {
+case only([Int])
+}
+
+struct NotEquatable { }
+
+enum ArrayOfNotEquatables : Equatable { // expected-error{{type 'ArrayOfNotEquatables' does not conform to protocol 'Equatable'}}
+case only([NotEquatable])
+}
+
 // FIXME: Remove -verify-ignore-unknown.
 // <unknown>:0: error: unexpected error produced: invalid redeclaration of 'hashValue'
 // <unknown>:0: error: unexpected note produced: candidate has non-matching type '(Foo, Foo) -> Bool'

test/Sema/enum_raw_representable.swift

@@ -78,8 +78,6 @@ class Outer {
   let a: Int = E.a // expected-error {{cannot convert value of type 'Outer.E' to specified type 'Int'}}
 
   enum E : Array<Int> { // expected-error {{raw type 'Array<Int>' is not expressible by any literal}}
-  // expected-error@-1 {{'Outer.E' declares raw type 'Array<Int>', but does not conform to RawRepresentable and conformance could not be synthesized}}
-  // expected-error@-2 {{RawRepresentable conformance cannot be synthesized because raw type 'Array<Int>' is not Equatable}}
     case a
   }
 }
@@ -146,3 +144,11 @@ func rdar32432253(_ condition: Bool = false) {
   let _ = choice == "bar"
   // expected-error@-1 {{cannot convert value of type 'E_32431165' to expected argument type 'String'}} {{11-11=}} {{17-17=.rawValue}}
 }
+
+
+struct NotEquatable { }
+
+enum ArrayOfNewEquatable : Array<NotEquatable> { }
+// expected-error@-1{{raw type 'Array<NotEquatable>' is not expressible by any literal}}
+// expected-error@-2{{'ArrayOfNewEquatable' declares raw type 'Array<NotEquatable>', but does not conform to RawRepresentable and conformance could not be synthesized}}
+// expected-error@-3{{RawRepresentable conformance cannot be synthesized because raw type 'Array<NotEquatable>' is not Equatable}}

test/expr/unary/keypath/salvage-with-other-type-errors.swift

@@ -51,7 +51,8 @@ protocol Bindable: class { }
 
 extension Bindable {
   func test<Value>(to targetKeyPath: ReferenceWritableKeyPath<Self, Value>, change: Value?) {
-    if self[keyPath:targetKeyPath] != change { // expected-error{{cannot convert value of type 'Value' to expected argument type '_OptionalNilComparisonType'}}
+    if self[keyPath:targetKeyPath] != change {  // expected-error{{}}
+      // expected-note@-1{{overloads for '!=' exist with these partially matching parameter lists: (Self, Self), (_OptionalNilComparisonType, Wrapped?)}}
       self[keyPath: targetKeyPath] = change!
     }
   }

test/expr/unary/selector/selector.swift

@@ -134,7 +134,7 @@ default:
 }
 
 switch optionalSel {
-case #selector(SR1827.bar): // expected-error{{expression pattern of type 'Selector' cannot match values of type 'Selector?'}} {{27-27=?}}
+case #selector(SR1827.bar):
   break
 case #selector(SR1827.bar)!: // expected-error{{cannot force unwrap value of non-optional type 'Selector'}}
   break

test/stdlib/ArrayDiagnostics.swift

@@ -5,7 +5,9 @@ class NotEquatable {}
 func test_ArrayOfNotEquatableIsNotEquatable() {
   var a = [ NotEquatable(), NotEquatable() ]
   // FIXME: This is an awful error.
-  if a == a {} // expected-error {{binary operator '==' cannot be applied to two '[NotEquatable]' operands}}
-  // expected-note @-1 {{overloads for '==' exist with these partially matching parameter lists: }}
+  if a == a {} // expected-error {{'<Self where Self : Equatable> (Self.Type) -> (Self, Self) -> Bool' requires that 'NotEquatable' conform to 'Equatable'}}
+  // expected-error@-1{{type 'NotEquatable' does not conform to protocol 'Equatable'}}
+  // expected-note @-2 {{requirement specified as 'NotEquatable' : 'Equatable'}}
+  // expected-note@-3{{requirement from conditional conformance of '[NotEquatable]' to 'Equatable'}}
 }