[interop][SwiftToCxx] retain class values when a C++ class reference is copy constructed

Author: hyp

lib/PrintAsClang/PrintClangClassType.cpp

@@ -44,6 +44,14 @@ void ClangClassTypePrinter::printClassTypeDecl(
   os << "() { swift::" << cxx_synthesis::getCxxImplNamespaceName()
      << "::swift_release(_opaquePointer); }\n";
 
+  os << "  inline ";
+  printer.printBaseName(typeDecl);
+  os << "(const ";
+  printer.printBaseName(typeDecl);
+  os << "& other) noexcept : _opaquePointer(other._opaquePointer) { swift::"
+     << cxx_synthesis::getCxxImplNamespaceName()
+     << "::swift_retain(_opaquePointer); }\n";
+
   // FIXME: move semantics should be restricted?
   os << "  inline ";
   printer.printBaseName(typeDecl);

test/Interop/SwiftToCxx/class/swift-class-execution.cpp

@@ -63,6 +63,17 @@ int main() {
 // CHECK-NEXT: init ClassWithIntField
 // CHECK-NEXT: destroy ClassWithIntField
 // CHECK-NEXT: ClassWithIntField: -11;
+// CHECK-NEXT: destroy ClassWithIntField
+
+  {
+    auto x = returnClassWithIntField();
+    {
+      auto x2 = x;
+      assert(getRetainCount(x) == 2);
+    }
+    assert(getRetainCount(x) == 1);
+  }
+// CHECK-NEXT: init ClassWithIntField
 // CHECK-NEXT: destroy ClassWithIntField
   return 0;
 }

test/Interop/SwiftToCxx/class/swift-class-in-cxx.swift

@@ -34,6 +34,7 @@ public final class ClassWithIntField {
 // CHECK-NEXT: class ClassWithIntField final {
 // CHECK-NEXT: public:
 // CHECK-NEXT:   inline ~ClassWithIntField() { swift::_impl::swift_release(_opaquePointer); }
+// CHECK-NEXT:   inline ClassWithIntField(const ClassWithIntField& other) noexcept : _opaquePointer(other._opaquePointer) { swift::_impl::swift_retain(_opaquePointer); } 
 // CHECK-NEXT:   inline ClassWithIntField(ClassWithIntField&&) noexcept = default;
 // CHECK-NEXT: private:
 // CHECK-NEXT:   inline ClassWithIntField(void * _Nonnull ptr) noexcept : _opaquePointer(ptr) {}