[SwiftToCxx] Implementing the Swift Error representation in C++

Author: Robertorosmaninho

lib/PrintAsClang/PrintSwiftToClangCoreScaffold.cpp

@@ -158,7 +158,7 @@ static void printTypeMetadataResponseType(SwiftToClangInteropContext &ctx,
 
 void printCxxNaiveException(raw_ostream &os) {
   os << "/// Naive exception class that should be thrown\n";
-  os << "class NaiveException {\n";
+  os << "class NaiveException : public swift::Error {\n";
   os << "public:\n";
   os << "  inline NaiveException(const char * _Nonnull msg) noexcept : "
      << "msg_(msg) { }\n";

stdlib/public/SwiftShims/_SwiftCxxInteroperability.h

@@ -32,6 +32,10 @@ extern "C" void *_Nonnull swift_retain(void *_Nonnull) noexcept;
 
 extern "C" void swift_release(void *_Nonnull) noexcept;
 
+extern "C" void *_Nonnull swift_errorRetain(void *_Nonnull swiftError) noexcept;
+
+extern "C" void swift_errorRelease(void *_Nonnull swiftError) noexcept;
+
 inline void *_Nonnull opaqueAlloc(size_t size, size_t align) noexcept {
 #if defined(_WIN32)
   void *r = _aligned_malloc(size, align);
@@ -172,6 +176,29 @@ template <class T> inline void *_Nonnull getOpaquePointer(T &value) {
   return reinterpret_cast<void *>(&value);
 }
 
+namespace swift {
+class Error {
+public:
+  Error() {}
+  ~Error() {
+    if (opaqueValue)
+      swift_errorRelease(opaqueValue);
+  }
+  void* _Nonnull getPointerToOpaquePointer() { return opaqueValue; }
+  Error(Error &&other) : opaqueValue(other.opaqueValue) {
+    other.opaqueValue = nullptr;
+  }
+  Error(const Error &other) {
+    if (other.opaqueValue)
+      swift_errorRetain(other.opaqueValue);
+    opaqueValue = other.opaqueValue;
+  }
+
+private:
+  void * _Nonnull opaqueValue = nullptr;
+};
+}
+
 } // namespace _impl
 
 #pragma clang diagnostic pop

test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx.swift

@@ -99,7 +99,7 @@
 // CHECK-NEXT: #endif
 // CHECK-EMPTY:
 // CHECK-NEXT: /// Naive exception class that should be thrown
-// CHECK-NEXT: class NaiveException {
+// CHECK-NEXT: class NaiveException : public swift::Error {
 // CHECK-NEXT: public:
 // CHECK-NEXT: inline NaiveException(const char * _Nonnull msg) noexcept : msg_(msg) { }
 // CHECK-NEXT: inline NaiveException(NaiveException&& other) noexcept : msg_(other.msg_) { other.msg_ = nullptr; }