use placement new so we don't destory an enum twice

Author: WANGJIEKE

lib/PrintAsClang/DeclAndTypePrinter.cpp

@@ -466,9 +466,16 @@ class DeclAndTypePrinter::Implementation
             owningPrinter.outputLang);
         os << " get" << name << "() const {\n";
         os << "    if (!is" << name << "()) abort();\n";
-        os << "    auto thisCopy = *this;\n";
+        os << "    alignas(";
+        syntaxPrinter.printBaseName(ED);
+        os << ") unsigned char buffer[sizeof(";
+        syntaxPrinter.printBaseName(ED);
+        os << ")];\n";
+        os << "    auto *thisCopy = new(buffer) ";
+        syntaxPrinter.printBaseName(ED);
+        os << "(*this);\n";
         os << "    char * _Nonnull payloadFromDestruction = "
-              "thisCopy._destructiveProjectEnumData();\n";
+              "thisCopy->_destructiveProjectEnumData();\n";
         if (auto knownCxxType =
                 owningPrinter.typeMapping.getKnownCxxTypeInfo(firstTypeDecl)) {
           os << "    ";
@@ -480,7 +487,10 @@ class DeclAndTypePrinter::Implementation
                 "memcpy(&result, payloadFromDestruction, sizeof(result));\n";
           os << "    return result;\n";
         } else {
-          os << "    return " << cxx_synthesis::getCxxImplNamespaceName();
+          os << "    return ";
+          syntaxPrinter.printModuleNamespaceQualifiersIfNeeded(
+              firstTypeDecl->getModuleContext(), ED->getModuleContext());
+          os << cxx_synthesis::getCxxImplNamespaceName();
           os << "::";
           ClangValueTypePrinter::printCxxImplClassName(os, firstTypeDecl);
           os << "::returnNewValue([&](char * _Nonnull result) {\n";

lib/PrintAsClang/PrintAsClang.cpp

@@ -102,7 +102,8 @@ static void writePrologue(raw_ostream &out, ASTContext &ctx,
         out << "#include <cstdint>\n"
                "#include <cstddef>\n"
                "#include <cstdbool>\n"
-               "#include <cstring>\n";
+               "#include <cstring>\n"
+               "#include <new>\n";
         out << "#include <stdlib.h>\n";
         out << "#if defined(_WIN32)\n#include <malloc.h>\n#endif\n";
       },

test/Interop/SwiftToCxx/enums/swift-enum-extract-payload.swift

@@ -111,24 +111,27 @@ public func makeUvw(_ x: Int) -> Uvw {
 // CHECK: class PrimitivePayload final {
 // CHECK:      inline int64_t getX() const {
 // CHECK-NEXT:   if (!isX()) abort();
-// CHECK-NEXT:   auto thisCopy = *this;
-// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy._destructiveProjectEnumData();
+// CHECK-NEXT:   alignas(PrimitivePayload) unsigned char buffer[sizeof(PrimitivePayload)];
+// CHECK-NEXT:   auto *thisCopy = new(buffer) PrimitivePayload(*this);
+// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy->_destructiveProjectEnumData();
 // CHECK-NEXT:   int64_t result;
 // CHECK-NEXT:   memcpy(&result, payloadFromDestruction, sizeof(result));
 // CHECK-NEXT:   return result;
 // CHECK-NEXT: }
 // CHECK:      inline double getY() const {
 // CHECK-NEXT:   if (!isY()) abort();
-// CHECK-NEXT:   auto thisCopy = *this;
-// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy._destructiveProjectEnumData();
+// CHECK-NEXT:   alignas(PrimitivePayload) unsigned char buffer[sizeof(PrimitivePayload)];
+// CHECK-NEXT:   auto *thisCopy = new(buffer) PrimitivePayload(*this);
+// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy->_destructiveProjectEnumData();
 // CHECK-NEXT:   double result;
 // CHECK-NEXT:   memcpy(&result, payloadFromDestruction, sizeof(result));
 // CHECK-NEXT:   return result;
 // CHECK-NEXT: }
 // CHECK:      inline bool getZ() const {
 // CHECK-NEXT:   if (!isZ()) abort();
-// CHECK-NEXT:   auto thisCopy = *this;
-// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy._destructiveProjectEnumData();
+// CHECK-NEXT:   alignas(PrimitivePayload) unsigned char buffer[sizeof(PrimitivePayload)];
+// CHECK-NEXT:   auto *thisCopy = new(buffer) PrimitivePayload(*this);
+// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy->_destructiveProjectEnumData();
 // CHECK-NEXT:   bool result;
 // CHECK-NEXT:   memcpy(&result, payloadFromDestruction, sizeof(result));
 // CHECK-NEXT:   return result;
@@ -173,16 +176,18 @@ public func makeUvw(_ x: Int) -> Uvw {
 // CHECK: class Xyz final {
 // CHECK:      inline Foo getFirst() const {
 // CHECK-NEXT:   if (!isFirst()) abort();
-// CHECK-NEXT:   auto thisCopy = *this;
-// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy._destructiveProjectEnumData();
+// CHECK-NEXT:   alignas(Xyz) unsigned char buffer[sizeof(Xyz)];
+// CHECK-NEXT:   auto *thisCopy = new(buffer) Xyz(*this);
+// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy->_destructiveProjectEnumData();
 // CHECK-NEXT:   return _impl::_impl_Foo::returnNewValue([&](char * _Nonnull result) {
 // CHECK-NEXT:     _impl::_impl_Foo::initializeWithTake(result, payloadFromDestruction);
 // CHECK-NEXT:   });
 // CHECK-NEXT: }
 // CHECK:      inline Bar getThird() const {
 // CHECK-NEXT:   if (!isThird()) abort();
-// CHECK-NEXT:   auto thisCopy = *this;
-// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy._destructiveProjectEnumData();
+// CHECK-NEXT:   alignas(Xyz) unsigned char buffer[sizeof(Xyz)];
+// CHECK-NEXT:   auto *thisCopy = new(buffer) Xyz(*this);
+// CHECK-NEXT:   char * _Nonnull payloadFromDestruction = thisCopy->_destructiveProjectEnumData();
 // CHECK-NEXT:   return _impl::_impl_Bar::returnNewValue([&](char * _Nonnull result) {
 // CHECK-NEXT:     _impl::_impl_Bar::initializeWithTake(result, payloadFromDestruction);
 // CHECK-NEXT:   });