Remove final in protocol extensions

include/swift/AST/DiagnosticsSema.def

@@ -1988,6 +1988,9 @@ ERROR(override_static,none,
 ERROR(member_cannot_be_final,none,
       "only classes and class members may be marked with 'final'",
       ())
+WARNING(protocol_extension_cannot_be_final,none,
+      "functions in a protocol extension do not need to be marked with 'final'",
+      ())
 
 ERROR(final_not_allowed_here,none,
       "'final' may only be applied to classes, properties, methods, and "

lib/Sema/TypeCheckAttr.cpp

@@ -182,15 +182,20 @@ class AttributeEarlyChecker : public AttributeVisitor<AttributeEarlyChecker> {
     if (isa<ClassDecl>(D))
       return;
 
-    // 'final' only makes sense in the context of a class
-    // declaration or a protocol extension.  Reject it on global functions,
-    // structs, enums, etc.
-    if (D->getDeclContext()->getAsProtocolExtensionContext()) {
-      // Accept and remove the 'final' attribute from members of protocol
-      // extensions.
+    // 'final' only makes sense in the context of a class declaration.
+    // Reject it on global functions, protocols, structs, enums, etc.
+    if (!D->getDeclContext()->getAsClassOrClassExtensionContext()) {
+      if (D->getDeclContext()->getAsProtocolExtensionContext())
+        TC.diagnose(attr->getLocation(), 
+          diag::protocol_extension_cannot_be_final)
+          .fixItRemove(attr->getRange());
+      else
+        TC.diagnose(attr->getLocation(), diag::member_cannot_be_final)
+          .fixItRemove(attr->getRange());
+
+      // Remove the attribute so child declarations are not flagged as final
+      // and duplicate the error message.
       D->getAttrs().removeAttribute(attr);
-    } else if (!D->getDeclContext()->getAsClassOrClassExtensionContext()) {
-      diagnoseAndRemoveAttr(attr, diag::member_cannot_be_final);
       return;
     }
   }
@@ -1008,7 +1013,8 @@ void AttributeChecker::visitFinalAttr(FinalAttr *attr) {
   // We currently only support final on var/let, func and subscript
   // declarations.
   if (!isa<VarDecl>(D) && !isa<FuncDecl>(D) && !isa<SubscriptDecl>(D)) {
-    TC.diagnose(attr->getLocation(), diag::final_not_allowed_here);
+    TC.diagnose(attr->getLocation(), diag::final_not_allowed_here)
+      .fixItRemove(attr->getRange());
     return;
   }
 
@@ -1017,7 +1023,8 @@ void AttributeChecker::visitFinalAttr(FinalAttr *attr) {
       unsigned Kind = 2;
       if (auto *VD = dyn_cast<VarDecl>(FD->getAccessorStorageDecl()))
         Kind = VD->isLet() ? 1 : 0;
-      TC.diagnose(attr->getLocation(), diag::final_not_on_accessors, Kind);
+      TC.diagnose(attr->getLocation(), diag::final_not_on_accessors, Kind)
+        .fixItRemove(attr->getRange());
       return;
     }
   }

stdlib/public/SDK/Foundation/NSError.swift

@@ -380,8 +380,8 @@ extension __BridgedNSError
 
 public extension __BridgedNSError 
     where Self: RawRepresentable, Self.RawValue: SignedInteger {
-  public final var _domain: String { return Self._nsErrorDomain }
-  public final var _code: Int { return Int(rawValue.toIntMax()) }
+  public var _domain: String { return Self._nsErrorDomain }
+  public var _code: Int { return Int(rawValue.toIntMax()) }
 
   public init?(rawValue: RawValue) {
     self = unsafeBitCast(rawValue, to: Self.self)
@@ -395,7 +395,7 @@ public extension __BridgedNSError
     self.init(rawValue: RawValue(IntMax(_bridgedNSError.code)))
   }
 
-  public final var hashValue: Int { return _code }
+  public var hashValue: Int { return _code }
 }
 
 // Allow two bridged NSError types to be compared.
@@ -408,8 +408,8 @@ extension __BridgedNSError
 
 public extension __BridgedNSError
     where Self: RawRepresentable, Self.RawValue: UnsignedInteger {
-  public final var _domain: String { return Self._nsErrorDomain }
-  public final var _code: Int {
+  public var _domain: String { return Self._nsErrorDomain }
+  public var _code: Int {
     return Int(bitPattern: UInt(rawValue.toUIntMax()))
   }
 
@@ -425,7 +425,7 @@ public extension __BridgedNSError
     self.init(rawValue: RawValue(UIntMax(UInt(_bridgedNSError.code))))
   }
 
-  public final var hashValue: Int { return _code }
+  public var hashValue: Int { return _code }
 }
 
 /// Describes a raw representable type that is bridged to a particular

test/Generics/existential_restrictions.swift

@@ -73,7 +73,7 @@ protocol Mine {}
 class M1: Mine {}
 class M2: Mine {}
 extension Collection where Iterator.Element : Mine {
-    final func takeAll() {}
+    func takeAll() {}
 }
 
 func foo() {

test/IRGen/protocol_extensions.sil

@@ -9,8 +9,8 @@ public protocol P1 {
 }
 
 extension P1 {
-  final func extP1a()
-  public final func extP1b()
+  func extP1a()
+  public func extP1b()
 }
 
 // CHECK-LABEL: define hidden swiftcc void @_TFP19protocol_extensions2P16extP1aUS0___fQPS0_FT_T_

test/IRGen/protocol_extensions_constrain.swift

@@ -27,7 +27,7 @@ public struct C2 : P2 {
 }
 
 extension P2 where Self.Index : P3 {
-  final public var bar: Bool {
+  public var bar: Bool {
 	  let i = startIndex
     return i.foo(i)
   }

test/Interpreter/protocol_extensions.swift

@@ -3,7 +3,7 @@
 
 // Extend a protocol with a property.
 extension Sequence {
-  final var myCount: Int {
+  var myCount: Int {
     var result = 0
     for _ in self {
       result += 1
@@ -17,7 +17,7 @@ print(["a", "b", "c", "d"].myCount)
 
 // Extend a protocol with a function.
 extension Collection {
-  final var myIndices: Range<Index> {
+  var myIndices: Range<Index> {
     return startIndex..<endIndex
   }
 
@@ -30,7 +30,7 @@ extension Collection {
 print(["a", "b", "c", "d"].clone().myCount)
 
 extension Sequence {
-  final public func myEnumerated() -> EnumeratedSequence<Self> {
+  public func myEnumerated() -> EnumeratedSequence<Self> {
     return self.enumerated()
   }
 }
@@ -43,7 +43,7 @@ for (index, element) in ["a", "b", "c"].myEnumerated() {
 }
 
 extension Sequence {
-  final public func myReduce<T>(
+  public func myReduce<T>(
     _ initial: T, combine: (T, Self.Iterator.Element) -> T
   ) -> T { 
     var result = initial
@@ -59,7 +59,7 @@ print([1, 2, 3, 4, 5].myReduce(0, combine: +))
 
 
 extension Sequence {
-  final public func myZip<S : Sequence>(_ s: S) -> Zip2Sequence<Self, S> {
+  public func myZip<S : Sequence>(_ s: S) -> Zip2Sequence<Self, S> {
     return Zip2Sequence(_sequence1: self, _sequence2: s)
   }
 }
@@ -75,14 +75,14 @@ for (a, b) in [1, 2, 3].myZip(["a", "b", "c"]) {
 extension MutableCollection
   where Self: RandomAccessCollection, Self.Iterator.Element : Comparable {
 
-  public final mutating func myPartition() -> Index {
+  public mutating func myPartition() -> Index {
     let first = self.first
     return self.partition(by: { $0 >= first! })
   }
 }
 
 extension RangeReplaceableCollection {
-  public final func myJoin<S : Sequence where S.Iterator.Element == Self>(
+  public func myJoin<S : Sequence where S.Iterator.Element == Self>(
     _ elements: S
   ) -> Self {
     var result = Self()
@@ -107,7 +107,7 @@ print(
 
 // Constrained extensions for specific types.
 extension Collection where Self.Iterator.Element == String {
-  final var myCommaSeparatedList: String {
+  var myCommaSeparatedList: String {
     if startIndex == endIndex { return "" }
 
     var result = ""
@@ -133,7 +133,7 @@ protocol ExistP1 {
 }
 
 extension ExistP1 {
-  final func runExistP1() {
+  func runExistP1() {
     print("runExistP1")
     self.existP1()
   }
@@ -167,7 +167,7 @@ protocol P {
 }
 
 extension P {
-  final var extValue: Bool {
+  var extValue: Bool {
     get { return getValue() }
     set(newValue) { setValue(newValue) }
   }

test/NameBinding/reference-dependencies.swift

@@ -107,12 +107,12 @@ typealias MyArray = Array<Bool>
 
 // CHECK-DAG: "ExpressibleByArrayLiteral"
 extension ExpressibleByArrayLiteral {
-  final func useless() {}
+  func useless() {}
 }
 
 // CHECK-DAG: OtherFileElementType
 extension ExpressibleByArrayLiteral where Element == OtherFileElementType {
-  final func useless2() {}
+  func useless2() {}
 }
 
 // CHECK-DAG: "IntegerLiteralType"

test/NameBinding/scope_map_lookup.swift

@@ -73,14 +73,14 @@ class Superclass {
 protocol PConstrained4 { }
 
 extension PConstrained4 where Self : Superclass {
-  final func testFoo() -> Foo {
+  func testFoo() -> Foo {
     foo()
     self.foo()
 
     return Foo(5)
   }
 
-  final static func testBar() {
+  static func testBar() {
     bar()
     self.bar()
   }

test/SILGen/boxed_existentials.swift

@@ -98,7 +98,7 @@ func test_property_of_lvalue(_ x: Error) -> String {
 // CHECK:         return [[RESULT]]
 // CHECK:      } // end sil function '_T018boxed_existentials23test_property_of_lvalueSSs5Error_pF'
 extension Error {
-  final func extensionMethod() { }
+  func extensionMethod() { }
 }
 
 // CHECK-LABEL: sil hidden @_T018boxed_existentials21test_extension_methodys5Error_pF

test/SILGen/guaranteed_self.swift

@@ -445,7 +445,7 @@ public protocol SequenceDefaults {
 }
 
 extension SequenceDefaults {
-  public final func _constrainElement(_: FakeGenerator.Element) {}
+  public func _constrainElement(_: FakeGenerator.Element) {}
 }
 
 public protocol Sequence : SequenceDefaults {

test/SILGen/protocol_extensions.swift

@@ -12,7 +12,7 @@ struct Box {
 extension P1 {
   // CHECK-LABEL: sil hidden @_T019protocol_extensions2P1PAAE6extP1a{{[_0-9a-zA-Z]*}}F : $@convention(method) <Self where Self : P1> (@in_guaranteed Self) -> () {
   // CHECK: bb0([[SELF:%[0-9]+]] : $*Self):
-  final func extP1a() {
+  func extP1a() {
     // CHECK: [[WITNESS:%[0-9]+]] = witness_method $Self, #P1.reqP1a!1 : {{.*}} : $@convention(witness_method) <τ_0_0 where τ_0_0 : P1> (@in_guaranteed τ_0_0) -> ()
     // CHECK-NEXT: apply [[WITNESS]]<Self>([[SELF]]) : $@convention(witness_method) <τ_0_0 where τ_0_0 : P1> (@in_guaranteed τ_0_0) -> ()
     reqP1a()
@@ -21,7 +21,7 @@ extension P1 {
 
   // CHECK-LABEL: sil @_T019protocol_extensions2P1PAAE6extP1b{{[_0-9a-zA-Z]*}}F : $@convention(method) <Self where Self : P1> (@in_guaranteed Self) -> () {
   // CHECK: bb0([[SELF:%[0-9]+]] : $*Self):
-  public final func extP1b() {
+  public func extP1b() {
     // CHECK: [[FN:%[0-9]+]] = function_ref @_T019protocol_extensions2P1PAAE6extP1a{{[_0-9a-zA-Z]*}}F : $@convention(method) <τ_0_0 where τ_0_0 : P1> (@in_guaranteed τ_0_0) -> ()
     // CHECK-NEXT: apply [[FN]]<Self>([[SELF]]) : $@convention(method) <τ_0_0 where τ_0_0 : P1> (@in_guaranteed τ_0_0) -> ()
     extP1a()
@@ -36,7 +36,7 @@ extension P1 {
     set {}
   }
 
-  final func callSubscript() -> Int {
+  func callSubscript() -> Int {
     // But here we have to do a witness method call:
 
     // CHECK-LABEL: sil hidden @_T019protocol_extensions2P1PAAE13callSubscript{{[_0-9a-zA-Z]*}}F
@@ -474,24 +474,24 @@ func testG<T>(_ m: GenericMetaHolder<T>, gg: G<T>.Type) {
 // Using protocol extension members with existentials
 // ----------------------------------------------------------------------------
 extension P1 {
-  final func f1() { }
+  func f1() { }
 
-  final subscript (i: Int64) -> Bool {
+  subscript (i: Int64) -> Bool {
     get { return true }
   }
 
-  final var prop: Bool {
+  var prop: Bool {
     get { return true }
   }
 
-  final func returnsSelf() -> Self { return self }
+  func returnsSelf() -> Self { return self }
 
-  final var prop2: Bool {
+  var prop2: Bool {
     get { return true }
     set { }
   }
 
-  final subscript (b: Bool) -> Bool {
+  subscript (b: Bool) -> Bool {
     get { return b }
     set { }
   }
@@ -641,7 +641,7 @@ func test_open_existential_semantics_opaque(_ guaranteed: P1,
 protocol CP1: class {}
 
 extension CP1 {
-  final func f1() { }
+  func f1() { }
 }
 
 func plusOneCP1() -> CP1 {}

test/SILGen/witnesses_canonical.swift

@@ -14,7 +14,7 @@ struct _S<T : _CDT> : CT {
 }
 
 extension _CDT {
-  final subscript(b: Int) -> _S<Self> {
+  subscript(b: Int) -> _S<Self> {
     return _S(a: self, b: b)
   }
 }

test/SILOptimizer/devirt_extension.swift

@@ -3,7 +3,7 @@
 protocol DrawingElementDispatch {}
 
 extension DrawingElementDispatch {
-  final var boundingBox: Int32 {
+  var boundingBox: Int32 {
     return 0
   }
 }

test/Serialization/Inputs/def_class.swift

@@ -52,7 +52,7 @@ public protocol Resettable {
 }
 
 public extension Resettable {
-  final func doReset() { self.reset() }
+  func doReset() { self.reset() }
 }
 
 open class ResettableIntWrapper : Resettable {
@@ -80,7 +80,7 @@ public protocol PairLike {
 }
 
 public extension PairLike where FirstType : Cacheable {
-  final func cacheFirst() { }
+  func cacheFirst() { }
 }
 
 public protocol ClassProto : class {}

test/SourceKit/DocSupport/Inputs/cake.swift

@@ -17,7 +17,7 @@ public class C1 : Prot {
 public func genfoo<T1 : Prot, T2 : C1>(x ix: T1, y iy: T2) where T1.Element == Int, T2.Element == T1.Element {}
 
 public extension Prot where Self.Element == Int {
-  final func extfoo() {}
+  func extfoo() {}
 }
 
 public enum MyEnum : Int {