Merge pull request #7704 from KingOfBrian/bugfix/SR-4024

[Diagnostics] Do not report an override warning multiple times

Author: slavapestov

lib/Sema/TypeCheckDecl.cpp

@@ -6135,7 +6135,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     // it is in the same module, update the vtable.
     if (auto *baseDecl = dyn_cast<ClassDecl>(base->getDeclContext())) {
       if (baseDecl->hasKnownSwiftImplementation() && 
-          !base->isDynamic() &&
+          !base->isDynamic() && !isKnownObjC &&
           override->getDeclContext()->isExtensionContext()) {
         // For compatibility, only generate a warning in Swift 3
         TC.diagnose(override, (TC.Context.isSwiftVersion3()

test/decl/inherit/override.swift

@@ -9,6 +9,9 @@ class A {
 
   @objc func f3() { } // expected-note{{overridden declaration is here}}
   @objc func f4() -> ObjCClassA { } // expected-note{{overridden declaration is here}}
+  @objc var v1: Int { return 0 } // expected-note{{overridden declaration is here}}
+  @objc var v2: Int { return 0 } // expected-note{{overridden declaration is here}}
+  @objc var v3: Int = 0 // expected-note{{overridden declaration is here}}
 
   dynamic func f3D() { }
   dynamic func f4D() -> ObjCClassA { }
@@ -30,6 +33,15 @@ extension B {
 
   override func f3() { } // expected-error{{cannot override a non-dynamic class declaration from an extension}}
   override func f4() -> ObjCClassB { } // expected-error{{cannot override a non-dynamic class declaration from an extension}}
+  override var v1: Int { return 1 } // expected-error{{cannot override a non-dynamic class declaration from an extension}}
+  override var v2: Int { // expected-error{{cannot override a non-dynamic class declaration from an extension}}
+    get { return 1 }
+    set { }
+  }
+  override var v3: Int { // expected-error{{cannot override a non-dynamic class declaration from an extension}}
+    willSet { }
+    didSet { }
+  }
 
   override func f3D() { }
   override func f4D() -> ObjCClassB { }