[Sema] Adding deprecation warning for protocol inheritance 'class' syntax

include/swift/AST/DiagnosticsSema.def

@@ -2611,6 +2611,9 @@ WARNING(duplicate_anyobject_class_inheritance,none,
   "redundant inheritance from 'AnyObject' and Swift 3 'class' keyword", ())
 ERROR(inheritance_from_protocol_with_superclass,none,
   "inheritance from class-constrained protocol composition type %0", (Type))
+WARNING(anyobject_class_inheritance_deprecated,none,
+  "using 'class' keyword for protocol inheritance is deprecated; "
+  "use 'AnyObject' instead", ())
 ERROR(multiple_inheritance,none,
   "multiple inheritance from classes %0 and %1", (Type, Type))
 ERROR(inheritance_from_non_protocol_or_class,none,

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -179,6 +179,20 @@ static void checkInheritanceClause(
     // GenericSignatureBuilder (for protocol inheritance) or the
     // ConformanceLookupTable (for protocol conformance).
     if (inheritedTy->isAnyObject()) {
+      // Warn inherited AnyObject written as 'class' as deprecated
+      // for Swift >= 5.
+      auto sourceRange = inherited.getSourceRange();
+      bool isWrittenAsClass =
+          (isa<ProtocolDecl>(decl) || isa<AbstractTypeParamDecl>(decl)) &&
+          Lexer::getTokenAtLocation(ctx.SourceMgr, sourceRange.Start)
+              .is(tok::kw_class);
+      if (ctx.LangOpts.isSwiftVersionAtLeast(5) && isWrittenAsClass) {
+        diags
+            .diagnose(sourceRange.Start,
+                      diag::anyobject_class_inheritance_deprecated)
+            .fixItReplace(sourceRange, "AnyObject");
+      }
+
       if (inheritedAnyObject) {
         // If the first occurrence was written as 'class', downgrade the error
         // to a warning in such case for backward compatibility with

stdlib/public/Darwin/CoreFoundation/CoreFoundation.swift

@@ -12,7 +12,7 @@
 
 @_exported import CoreFoundation
 
-public protocol _CFObject: class, Hashable {}
+public protocol _CFObject: AnyObject, Hashable {}
 extension _CFObject {
   public var hashValue: Int {
     return Int(bitPattern: CFHash(self))

stdlib/public/core/BridgeObjectiveC.swift

@@ -681,7 +681,7 @@ public func _conditionallyBridgeFromObjectiveC_bridgeable<T:_ObjectiveCBridgeabl
 }
 
 public // SPI(Foundation)
-protocol _NSSwiftValue: class {
+protocol _NSSwiftValue: AnyObject {
   init(_ value: Any)
   var value: Any { get }
   static var null: AnyObject { get }

stdlib/public/core/ExistentialCollection.swift

@@ -1641,7 +1641,7 @@ extension AnyRandomAccessCollection {
 //===----------------------------------------------------------------------===//
 
 @usableFromInline
-internal protocol _AnyIndexBox: class {
+internal protocol _AnyIndexBox: AnyObject {
   var _typeID: ObjectIdentifier { get }
 
   func _unbox<T: Comparable>() -> T?

test/Parse/try_swift5.swift

@@ -263,7 +263,7 @@ let _: Int??? = try? producer.produceDoubleOptionalInt() // good
 let _: String = try? producer.produceDoubleOptionalInt() // expected-error {{cannot convert value of type 'Int??' to specified type 'String'}}
 
 // rdar://problem/46742002
-protocol Dummy : class {}
+protocol Dummy : AnyObject {}
 
 class F<T> {
   func wait() throws -> T { fatalError() }

test/decl/func/dynamic_self.swift

@@ -44,7 +44,7 @@ extension P0 {
   }
 }
 
-protocol P1: class {
+protocol P1: AnyObject {
   func f() -> Self // okay
 
   func g(_ ds: Self) // okay

test/decl/inherit/inherit_anyobject_protocol.swift

@@ -0,0 +1,7 @@
+// RUN: %target-typecheck-verify-swift 
+
+protocol P: class {}
+protocol P1: AnyObject {}
+protocol P2 {}
+protocol P3: class, P2 {} 
+protocol P4: P2, class {} // expected-error {{'class' must come first in the requirement list}}

test/decl/inherit/inherit_anyobject_protocol_swift5.swift

@@ -0,0 +1,10 @@
+// RUN: %target-typecheck-verify-swift -swift-version 5
+
+protocol P: class {}
+// expected-warning@-1 {{using 'class' keyword for protocol inheritance is deprecated; use 'AnyObject' instead}} {{13-18=AnyObject}} 
+protocol P1: AnyObject {}
+protocol P2 {}
+protocol P3: class, P2 {} 
+// expected-warning@-1 {{using 'class' keyword for protocol inheritance is deprecated; use 'AnyObject' instead}} {{14-19=AnyObject}}
+protocol P4: P2, class {} // expected-error {{'class' must come first in the requirement list}}
+// expected-warning@-1 {{using 'class' keyword for protocol inheritance is deprecated; use 'AnyObject' instead}} {{18-23=AnyObject}}

test/stdlib/Builtins.swift

@@ -165,7 +165,7 @@ tests.test("array value witnesses") {
   expectEqual(NoisyLifeCount, NoisyDeathCount)
 }
 
-protocol Classy : class {}
+protocol Classy : AnyObject {}
 class A : Classy {}
 class B : A {}
 class C : B {}

test/stdlib/Error.swift

@@ -15,7 +15,7 @@ protocol OtherProtocol {
   var otherProperty: String { get }
 }
 
-protocol OtherClassProtocol : class {
+protocol OtherClassProtocol : AnyObject {
   var otherClassProperty: String { get }
 }
 

test/stdlib/ErrorBridged.swift

@@ -22,7 +22,7 @@ protocol OtherProtocol {
   var otherProperty: String { get }
 }
 
-protocol OtherClassProtocol : class {
+protocol OtherClassProtocol : AnyObject {
   var otherClassProperty: String { get }
 }
 

test/stdlib/Mirror.swift

@@ -514,7 +514,7 @@ mirrors.test("struct/WrapNSArray") {
 // Check that Mirror correctly reflects weak/unowned refs to both
 // Swift and ObjC objects from Swift structs and classes.
 
-protocol WeakUnownedTestsP1: class {
+protocol WeakUnownedTestsP1: AnyObject {
   func f1() -> Int
 }
 

test/stdlib/Reflection.swift

@@ -118,7 +118,7 @@ print("Fooable double:")
 fooable = 2.5
 dump(fooable)
 
-protocol Barrable : class {}
+protocol Barrable : AnyObject {}
 extension Best: Barrable {}
 
 // CHECK-LABEL: Barrable class:

test/stdlib/Runtime.swift.gyb

@@ -534,7 +534,7 @@ Runtime.test("abstraction barrier on casting generic param bound to existential"
 class Malkovich: Malkovichable {
   var malkovich: String { return "malkovich" }
 }
-protocol Malkovichable: class {
+protocol Malkovichable: AnyObject {
   var malkovich: String { get }
 }
 

test/stdlib/WeakMirror.swift

@@ -35,7 +35,7 @@ class NativeSwiftClass : NativeClassBoundExistential {
   }
 }
 
-protocol NativeClassBoundExistential : class {
+protocol NativeClassBoundExistential : AnyObject {
   var x: Int { get }
 }
 class NativeSwiftClassHasWeak {
@@ -123,7 +123,7 @@ mirrors.test("class/NativeSwiftClassHasNativeWeakReferenceNoLeak") {
 
 import Foundation
 
-@objc protocol ObjCClassExistential : class {
+@objc protocol ObjCClassExistential : AnyObject {
   var weakProperty: AnyObject? { get set }
   var x: Int { get }
 }