[interop][SwiftToCxx] add support for passing and returning class values to generic functions

lib/PrintAsClang/ClangSyntaxPrinter.cpp

@@ -12,6 +12,7 @@
 
 #include "ClangSyntaxPrinter.h"
 #include "swift/ABI/MetadataValues.h"
+#include "swift/AST/Decl.h"
 #include "swift/AST/Module.h"
 
 using namespace swift;
@@ -168,3 +169,14 @@ void ClangSyntaxPrinter::printValueWitnessTableAccessSequenceFromTypeMetadata(
   os << "auto *" << vwTableVariable << " = *vwTableAddr;\n";
   os << "#endif\n";
 }
+
+void ClangSyntaxPrinter::printCTypeMetadataTypeFunction(
+    const NominalTypeDecl *typeDecl, StringRef typeMetadataFuncName) {
+  os << "// Type metadata accessor for " << typeDecl->getNameStr() << "\n";
+  os << "SWIFT_EXTERN ";
+  printSwiftImplQualifier();
+  os << "MetadataResponseTy " << typeMetadataFuncName << '(';
+  printSwiftImplQualifier();
+  os << "MetadataRequestTy)";
+  os << " SWIFT_NOEXCEPT SWIFT_CALL;\n\n";
+}

lib/PrintAsClang/ClangSyntaxPrinter.h

@@ -21,6 +21,7 @@
 namespace swift {
 
 class ModuleDecl;
+class NominalTypeDecl;
 
 namespace cxx_synthesis {
 
@@ -95,6 +96,10 @@ public:
   void printValueWitnessTableAccessSequenceFromTypeMetadata(
       StringRef metadataVariable, StringRef vwTableVariable, int indent);
 
+  /// Print the metadata accessor function for the given type declaration.
+  void printCTypeMetadataTypeFunction(const NominalTypeDecl *typeDecl,
+                                      StringRef typeMetadataFuncName);
+
 protected:
   raw_ostream &os;
 };

lib/PrintAsClang/PrintAsClang.cpp

@@ -105,6 +105,7 @@ static void writePrologue(raw_ostream &out, ASTContext &ctx,
                "#include <cstring>\n";
         out << "#include <stdlib.h>\n";
         out << "#include <new>\n";
+        out << "#include <type_traits>\n";
         // FIXME: Look for the header in the SDK.
         out << "// Look for the C++ interop support header relative to clang's resource dir:\n";
         out << "//  '<toolchain>/usr/lib/clang/<version>/include/../../../swift/shims'.\n";

lib/PrintAsClang/PrintClangClassType.cpp

@@ -14,6 +14,7 @@
 #include "ClangSyntaxPrinter.h"
 #include "PrintClangValueType.h"
 #include "swift/AST/Decl.h"
+#include "swift/IRGen/Linking.h"
 
 using namespace swift;
 
@@ -23,12 +24,20 @@ void ClangClassTypePrinter::printClassTypeDecl(
 
   ClangSyntaxPrinter printer(os);
 
+  auto typeMetadataFunc = irgen::LinkEntity::forTypeMetadataAccessFunction(
+      typeDecl->getDeclaredType()->getCanonicalType());
+  std::string typeMetadataFuncName = typeMetadataFunc.mangleAsString();
+
   // Print out a forward declaration of the "hidden" _impl class.
   printer.printNamespace(cxx_synthesis::getCxxImplNamespaceName(),
                          [&](raw_ostream &os) {
                            os << "class ";
                            printCxxImplClassName(os, typeDecl);
                            os << ";\n";
+                           // Print out special functions, like functions that
+                           // access type metadata.
+                           printer.printCTypeMetadataTypeFunction(
+                               typeDecl, typeMetadataFuncName);
                          });
 
   std::string baseClassName;
@@ -84,6 +93,48 @@ void ClangClassTypePrinter::printClassTypeDecl(
         os << "(ptr); }\n";
         os << "};\n";
       });
+
+  // FIXME: avoid popping out of the module's namespace here.
+  os << "} // end namespace \n\n";
+  os << "namespace swift {\n";
+
+  os << "#pragma clang diagnostic push\n";
+  os << "#pragma clang diagnostic ignored \"-Wc++17-extensions\"\n";
+  os << "template<>\n";
+  os << "static inline const constexpr bool isUsableInGenericContext<";
+  printer.printBaseName(typeDecl->getModuleContext());
+  os << "::";
+  printer.printBaseName(typeDecl);
+  os << "> = true;\n";
+  os << "#pragma clang diagnostic pop\n";
+
+  os << "template<>\n";
+  os << "inline void * _Nonnull getTypeMetadata<";
+  printer.printBaseName(typeDecl->getModuleContext());
+  os << "::";
+  printer.printBaseName(typeDecl);
+  os << ">() {\n";
+  os << "  return ";
+  printer.printBaseName(typeDecl->getModuleContext());
+  os << "::" << cxx_synthesis::getCxxImplNamespaceName()
+     << "::" << typeMetadataFuncName << "(0)._0;\n";
+  os << "}\n";
+  os << "namespace " << cxx_synthesis::getCxxImplNamespaceName() << "{\n";
+  os << "template<>\n";
+  os << "struct implClassFor<";
+  printer.printBaseName(typeDecl->getModuleContext());
+  os << "::";
+  printer.printBaseName(typeDecl);
+  os << "> { using type = ";
+  printer.printBaseName(typeDecl->getModuleContext());
+  os << "::" << cxx_synthesis::getCxxImplNamespaceName() << "::";
+  printCxxImplClassName(os, typeDecl);
+  os << "; };\n";
+  os << "} // namespace\n";
+  os << "} // namespace swift\n";
+  os << "\nnamespace ";
+  printer.printBaseName(typeDecl->getModuleContext());
+  os << " {\n";
 }
 
 void ClangClassTypePrinter::printClassTypeReturnScaffold(

lib/PrintAsClang/PrintClangFunction.cpp

@@ -574,12 +574,23 @@ void DeclAndTypeClangFunctionPrinter::printCxxThunkBody(
       !hasKnownOptionalNullableCxxMapping(resultTy)) {
     if (isGenericType(resultTy)) {
       // FIXME: Support returning value types.
-      os << "  T returnValue;\n";
       std::string returnAddress;
       llvm::raw_string_ostream ros(returnAddress);
       ros << "reinterpret_cast<void *>(&returnValue)";
+
+      os << "  if constexpr (std::is_base_of<::swift::"
+         << cxx_synthesis::getCxxImplNamespaceName()
+         << "::RefCountedClass, T>::value) {\n";
+      os << "  void *returnValue;\n  ";
+      printCallToCFunc(/*additionalParam=*/StringRef(ros.str()));
+      os << ";\n";
+      os << "  return ::swift::" << cxx_synthesis::getCxxImplNamespaceName()
+         << "::implClassFor<T>::type::makeRetained(returnValue);\n";
+      os << "  } else {\n";
+      os << "  T returnValue;\n";
       printCallToCFunc(/*additionalParam=*/StringRef(ros.str()));
       os << ";\n  return returnValue;\n";
+      os << "  }\n";
       return;
     }
     if (auto *classDecl = resultTy->getClassOrBoundGenericClass()) {

lib/PrintAsClang/PrintClangValueType.cpp

@@ -80,19 +80,6 @@ printCValueTypeStorageStruct(raw_ostream &os, const NominalTypeDecl *typeDecl,
   os << "};\n\n";
 }
 
-void printCTypeMetadataTypeFunction(raw_ostream &os,
-                                    const NominalTypeDecl *typeDecl,
-                                    StringRef typeMetadataFuncName) {
-  os << "// Type metadata accessor for " << typeDecl->getNameStr() << "\n";
-  os << "SWIFT_EXTERN ";
-  ClangSyntaxPrinter printer(os);
-  printer.printSwiftImplQualifier();
-  os << "MetadataResponseTy " << typeMetadataFuncName << '(';
-  printer.printSwiftImplQualifier();
-  os << "MetadataRequestTy)";
-  os << " SWIFT_NOEXCEPT SWIFT_CALL;\n\n";
-}
-
 void ClangValueTypePrinter::printValueTypeDecl(
     const NominalTypeDecl *typeDecl,
     llvm::function_ref<void(void)> bodyPrinter) {
@@ -124,8 +111,8 @@ void ClangValueTypePrinter::printValueTypeDecl(
 
                            // Print out special functions, like functions that
                            // access type metadata.
-                           printCTypeMetadataTypeFunction(os, typeDecl,
-                                                          typeMetadataFuncName);
+                           printer.printCTypeMetadataTypeFunction(
+                               typeDecl, typeMetadataFuncName);
                          });
 
   auto printEnumVWTableVariable = [&](StringRef metadataName = "metadata",

stdlib/public/SwiftShims/_SwiftCxxInteroperability.h

@@ -109,6 +109,16 @@ static inline const constexpr bool isUsableInGenericContext = false;
 /// Returns the type metadat for the given Swift type T.
 template <class T> inline void *_Nonnull getTypeMetadata();
 
+namespace _impl {
+
+/// Type trait that returns the `_impl::_impl_<T>` class type for the given
+/// class T.
+template <class T> struct implClassFor {
+  // using type = ...;
+};
+
+} // namespace _impl
+
 } // namespace swift
 #endif
 

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

@@ -28,6 +28,9 @@ public final class ClassWithIntField {
 // CHECK: namespace _impl {
 // CHECK-EMPTY:
 // CHECK-NEXT: class _impl_ClassWithIntField;
+// CHECK-NEXT: // Type metadata accessor for ClassWithIntField
+// CHECK-NEXT: SWIFT_EXTERN swift::_impl::MetadataResponseTy $s5Class0A12WithIntFieldCMa(swift::_impl::MetadataRequestTy) SWIFT_NOEXCEPT SWIFT_CALL;
+// CHECK-EMPTY:
 // CHECK-EMPTY:
 // CHECK-NEXT: } // namespace _impl
 // CHECK-EMPTY:
@@ -49,6 +52,26 @@ public final class ClassWithIntField {
 // CHECK-NEXT:};
 // CHECK-EMPTY:
 // CHECK-NEXT:} // namespace _impl
+// CHECK-EMPTY:
+// CHECK-NEXT: } // end namespace
+// CHECK-EMPTY:
+// CHECK-NEXT: namespace swift {
+// CHECK-NEXT: #pragma clang diagnostic push
+// CHECK-NEXT: #pragma clang diagnostic ignored "-Wc++17-extensions"
+// CHECK-NEXT: template<>
+// CHECK-NEXT: static inline const constexpr bool isUsableInGenericContext<Class::ClassWithIntField> = true;
+// CHECK-NEXT: #pragma clang diagnostic pop
+// CHECK-NEXT: template<>
+// CHECK-NEXT: inline void * _Nonnull getTypeMetadata<Class::ClassWithIntField>() {
+// CHECK-NEXT:   return Class::_impl::$s5Class0A12WithIntFieldCMa(0)._0;
+// CHECK-NEXT: }
+// CHECK-NEXT: namespace _impl{
+// CHECK-NEXT: template<>
+// CHECK-NEXT: struct implClassFor<Class::ClassWithIntField> { using type = Class::_impl::_impl_ClassWithIntField; };
+// CHECK-NEXT: } // namespace
+// CHECK-NEXT: } // namespace swift
+// CHECK-EMPTY:
+// CHECK-NEXT: namespace Class {
 
 // CHECK: inline ClassWithIntField passThroughClassWithIntField(const ClassWithIntField& x) noexcept SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT:  return _impl::_impl_ClassWithIntField::makeRetained(_impl::$s5Class011passThroughA12WithIntFieldyAA0adeF0CADF(::swift::_impl::_impl_RefCountedClass::getOpaquePointer(x)));

test/Interop/SwiftToCxx/generics/generic-function-execution.cpp

@@ -126,5 +126,35 @@ int main() {
     double x = -19.75;
     assert(genericRet(x) == -19.75);
   }
+
+  {
+    auto tc = createTestClass();
+    genericPrintFunction(tc);
+  }
+// CHECK-NEXT: TestClass value=Functions.TestClass
+// CHECK-NEXT: deinit TestClass
+
+  {
+    auto tc = createTestClass();
+    auto tc2 = genericRet(tc);
+    assert(swift::_impl::_impl_RefCountedClass::getOpaquePointer(tc) ==
+           swift::_impl::_impl_RefCountedClass::getOpaquePointer(tc2));
+    genericPrintFunction(tc2);
+  }
+// CHECK-NEXT: TestClass value=Functions.TestClass
+// CHECK-NEXT: deinit TestClass
+
+  {
+    auto tc = createTestClass();
+    auto tc2 = createTestClass();
+    const auto p1 = swift::_impl::_impl_RefCountedClass::getOpaquePointer(tc);
+    const auto p2 = swift::_impl::_impl_RefCountedClass::getOpaquePointer(tc2);
+    assert(p1 != p2);
+    genericSwap(tc, tc2);
+    assert(p2 == swift::_impl::_impl_RefCountedClass::getOpaquePointer(tc));
+    assert(p1 == swift::_impl::_impl_RefCountedClass::getOpaquePointer(tc2));
+  }
+// CHECK-NEXT: deinit TestClass
+// CHECK-NEXT: deinit TestClass
   return 0;
 }

test/Interop/SwiftToCxx/generics/generic-function-in-cxx.swift

@@ -31,6 +31,15 @@ public func genericRet<T>(_ x: T) -> T {
     return x
 }
 
+public class TestClass {
+    let field: Int
+
+    init() { field = 0 }
+    deinit { print("deinit TestClass") }
+}
+
+public func createTestClass() -> TestClass { return TestClass() }
+
 // CHECK: SWIFT_EXTERN void $s9Functions20genericPrintFunctionyyxlF(const void * _Nonnull x, void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericPrintFunction(_:)
 // CHECK-NEXT: SWIFT_EXTERN void $s9Functions32genericPrintFunctionMultiGenericyySi_xxSiq_tr0_lF(ptrdiff_t x, const void * _Nonnull t1, const void * _Nonnull t1p, ptrdiff_t y, const void * _Nonnull t2, void * _Nonnull , void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericPrintFunctionMultiGeneric(_:_:_:_:_:)
 // CHECK-NEXT: SWIFT_EXTERN void $s9Functions26genericPrintFunctionTwoArgyyx_SitlF(const void * _Nonnull x, ptrdiff_t y, void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericPrintFunctionTwoArg(_:_:)
@@ -60,10 +69,16 @@ public func genericRet<T>(_ x: T) -> T {
 // CHECK:      template<class T>
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T>
 // CHECK-NEXT: inline T genericRet(const T & x) noexcept SWIFT_WARN_UNUSED_RESULT {
-// CHECK-NEXT:   T returnValue;
-// CHECK-NEXT: _impl::$s9Functions10genericRetyxxlF(reinterpret_cast<void *>(&returnValue), reinterpret_cast<const void *>(&x), swift::getTypeMetadata<T>());
-// CHECK-NEXT:   return returnValue;
-// CHECK-NEXT: }
+// CHECK-NEXT:    if constexpr (std::is_base_of<::swift::_impl::RefCountedClass, T>::value) {
+// CHECK-NEXT:    void *returnValue;
+// CHECK-NEXT:    _impl::$s9Functions10genericRetyxxlF(reinterpret_cast<void *>(&returnValue), reinterpret_cast<const void *>(&x), swift::getTypeMetadata<T>());
+// CHECK-NEXT:    return ::swift::_impl::implClassFor<T>::type::makeRetained(returnValue);
+// CHECK-NEXT:    } else {
+// CHECK-NEXT:    T returnValue;
+// CHECK-NEXT:    _impl::$s9Functions10genericRetyxxlF(reinterpret_cast<void *>(&returnValue), reinterpret_cast<const void *>(&x), swift::getTypeMetadata<T>());
+// CHECK-NEXT:    return returnValue;
+// CHECK-NEXT:    }
+// CHECK-NEXT:  }
 
 // CHECK:      template<class T>
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T>

test/PrintAsCxx/empty.swift

@@ -31,6 +31,7 @@
 // CHECK-NEXT:  #include <cstring>
 // CHECK-NEXT:  #include <stdlib.h>
 // CHECK-NEXT:  #include <new>
+// CHECK-NEXT:  #include <type_traits>
 // CHECK-NEXT:  // Look for the C++ interop support header relative to clang's resource dir:
 // CHECK-NEXT:  // '<toolchain>/usr/lib/clang/<version>/include/../../../swift/shims'.
 // CHECK-NEXT:  #if __has_include(<../../../swift/shims/_SwiftCxxInteroperability.h>)