Address review comments.

Author: Gabor Horvath

lib/ClangImporter/ImportDecl.cpp

@@ -3017,6 +3017,10 @@ namespace {
               /*Obsoleted=*/{});
           classDecl->getAttrs().add(AvAttr);
         }
+
+        if (decl->isEffectivelyFinal())
+          classDecl->getAttrs().add(new (Impl.SwiftContext)
+                                    FinalAttr(/*IsImplicit=*/true));
       }
 
       // If this module is declared as a C++ module, try to synthesize

test/Interop/Cxx/foreign-reference/Inputs/inheritance.h

@@ -109,7 +109,7 @@ DerivedFromValueTypeAndAnnotated *returnDerivedFromValueTypeAndAnnotated() { //
     return new DerivedFromValueTypeAndAnnotated();
 }
 
-struct DerivedFromRefType : RefType {};
+struct DerivedFromRefType final : RefType {};
 DerivedFromRefType *returnDerivedFromRefType() {
     return new DerivedFromRefType();
 }
@@ -180,7 +180,7 @@ __attribute__((swift_attr("release:RCRelease"))) RefType {};
 
 RefType *returnRefType() { return new RefType(); }; // expected-warning {{'returnRefType' should be annotated with either SWIFT_RETURNS_RETAINED or SWIFT_RETURNS_UNRETAINED as it is returning a SWIFT_SHARED_REFERENC}}
 
-struct DerivedFromRefType : RefType {};
+struct DerivedFromRefType final : RefType {};
 DerivedFromRefType *returnDerivedFromRefType() { // TODO: rdar://145098078 Missing SWIFT_RETURNS_(UN)RETAINED annotation warning should trigger for inferred foreeign reference types as well
   return new DerivedFromRefType();
 };

test/Interop/Cxx/foreign-reference/Inputs/reference-counted.h

@@ -14,7 +14,7 @@ namespace NS {
 
 struct __attribute__((swift_attr("import_as_ref")))
 __attribute__((swift_attr("retain:LCRetain")))
-__attribute__((swift_attr("release:LCRelease"))) LocalCount {
+__attribute__((swift_attr("release:LCRelease"))) LocalCount final {
   int value = 0;
 
   static LocalCount *create() {

test/Interop/Cxx/foreign-reference/extensions.swift

@@ -3,10 +3,24 @@
 
 import ReferenceCounted
 
+protocol MyProto {
+    func foo() -> Self
+}
+
 extension NS.LocalCount {
     static func g() {}
 
     public func f() {
         Self.g()
     }
 }
+
+extension NS.LocalCount: MyProto {
+    public func foo() -> Self {
+        return self
+    }
+}
+
+let x = NS.LocalCount.create()
+x.f()
+let _ = x.foo()