Ensure that bridged types are indirectly returned on Windows ARM64

include/swift/AST/ASTBridging.h

@@ -81,6 +81,10 @@ class BridgedDeclBaseName {
   BridgedIdentifier Ident;
 
 public:
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedDeclBaseName() : Ident() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedDeclBaseName(swift::DeclBaseName baseName) : Ident(baseName.Ident) {}
 
@@ -107,6 +111,10 @@ class BridgedDeclNameRef {
   void *_Nonnull opaque;
 
 public:
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedDeclNameRef() : opaque() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedDeclNameRef(swift::DeclNameRef name) : opaque(name.getOpaqueValue()) {}
 
@@ -163,6 +171,10 @@ class BridgedASTContext {
   swift::ASTContext * _Nonnull Ctx;
 
 public:
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedASTContext() : Ctx() {}
+
 #ifdef USED_IN_CPP_SOURCE
   SWIFT_UNAVAILABLE("Use init(raw:) instead")
   BridgedASTContext(swift::ASTContext &ctx) : Ctx(&ctx) {}
@@ -390,6 +402,10 @@ class BridgedDiagnosticArgument {
   int64_t storage[3];
 
 public:
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedDiagnosticArgument() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedDiagnosticArgument(const swift::DiagnosticArgument &arg) {
     *reinterpret_cast<swift::DiagnosticArgument *>(&storage) = arg;
@@ -407,6 +423,10 @@ class BridgedDiagnosticFixIt {
   int64_t storage[7];
 
 public:
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedDiagnosticFixIt() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedDiagnosticFixIt(const swift::DiagnosticInfo::FixIt &fixit){
     *reinterpret_cast<swift::DiagnosticInfo::FixIt *>(&storage) = fixit;
@@ -1406,6 +1426,10 @@ class BridgedStmtConditionElement {
   void *_Nonnull Raw;
 
 public:
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedStmtConditionElement() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedStmtConditionElement(swift::StmtConditionElement elem)
       : Raw(elem.getOpaqueValue()) {}

include/swift/Basic/BasicBridging.h

@@ -23,6 +23,15 @@
 // Pure bridging mode does not permit including any C++/llvm/swift headers.
 // See also the comments for `BRIDGING_MODE` in the top-level CMakeLists.txt file.
 //
+//
+// Note: On Windows ARM64, how a C++ struct/class value type is
+// returned is sensitive to conditions including whether a
+// user-defined constructor exists, etc. See
+// https://learn.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=msvc-170#return-values
+// So, if a C++ struct/class type is returned as a value between Swift
+// and C++, we need to be careful to match the return convention
+// matches between the non-USED_IN_CPP_SOURCE (Swift) side and the
+// USE_IN_CPP_SOURCE (C++) side.
 #include "swift/Basic/BridgedSwiftObject.h"
 #include "swift/Basic/Compiler.h"
 
@@ -227,6 +236,10 @@ class BridgedOwnedString {
   size_t Length;
 
 public:
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedOwnedString() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedOwnedString(const std::string &stringToCopy);
 

include/swift/Parse/ParseBridging.h

@@ -30,6 +30,10 @@ class BridgedLegacyParser {
   swift::Parser *_Nonnull const handle;
 
 public:
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedLegacyParser() : handle(nullptr) {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedLegacyParser(swift::Parser &P) : handle(&P) {}
 

include/swift/SIL/SILBridging.h

@@ -83,6 +83,10 @@ struct BridgedResultInfo {
   swift::TypeBase * _Nonnull type;
   BridgedResultConvention convention;
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedResultInfo() {}
+
 #ifdef USED_IN_CPP_SOURCE
   inline static BridgedResultConvention
   castToResultConvention(swift::ResultConvention convention) {
@@ -100,6 +104,10 @@ struct OptionalBridgedResultInfo {
   swift::TypeBase * _Nullable type = nullptr;
   BridgedResultConvention convention = BridgedResultConvention::Indirect;
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  OptionalBridgedResultInfo() {}
+
 #ifdef USED_IN_CPP_SOURCE
   OptionalBridgedResultInfo(std::optional<swift::SILResultInfo> resultInfo) {
     if (resultInfo) {
@@ -114,6 +122,10 @@ struct OptionalBridgedResultInfo {
 struct BridgedResultInfoArray {
   BridgedArrayRef resultInfoArray;
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedResultInfoArray() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedResultInfoArray(llvm::ArrayRef<swift::SILResultInfo> results)
     : resultInfoArray(results) {}
@@ -217,6 +229,10 @@ struct BridgedParameterInfo {
 struct BridgedParameterInfoArray {
   BridgedArrayRef parameterInfoArray;
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedParameterInfoArray() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedParameterInfoArray(llvm::ArrayRef<swift::SILParameterInfo> parameters)
     : parameterInfoArray(parameters) {}
@@ -235,6 +251,10 @@ struct BridgedParameterInfoArray {
 struct BridgedYieldInfoArray {
   BridgedArrayRef yieldInfoArray;
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedYieldInfoArray() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedYieldInfoArray(llvm::ArrayRef<swift::SILYieldInfo> yields)
     : yieldInfoArray(yields) {}
@@ -255,6 +275,10 @@ struct BridgedLifetimeDependenceInfo {
   SwiftUInt targetIndex;
   bool immortal;
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedLifetimeDependenceInfo() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedLifetimeDependenceInfo(swift::LifetimeDependenceInfo info)
       : inheritLifetimeParamIndices(info.getInheritIndices()),
@@ -273,6 +297,10 @@ struct BridgedLifetimeDependenceInfo {
 struct BridgedLifetimeDependenceInfoArray {
   BridgedArrayRef lifetimeDependenceInfoArray;
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedLifetimeDependenceInfoArray() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedLifetimeDependenceInfoArray(
       llvm::ArrayRef<swift::LifetimeDependenceInfo> lifetimeDependenceInfo)
@@ -373,6 +401,10 @@ struct BridgedType {
   struct EnumElementIterator {
     uint64_t storage[4];
 
+    // Ensure that this struct value type will be indirectly returned on
+    // Windows ARM64
+    EnumElementIterator() {}
+
 #ifdef USED_IN_CPP_SOURCE
     EnumElementIterator(swift::EnumDecl::ElementRange::iterator i) {
       static_assert(sizeof(EnumElementIterator) >= sizeof(swift::EnumDecl::ElementRange::iterator));
@@ -386,6 +418,10 @@ struct BridgedType {
     SWIFT_IMPORT_UNSAFE BRIDGED_INLINE EnumElementIterator getNext() const;
   };
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedType() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedType(swift::SILType t) : opaqueValue(t.getOpaqueValue()) {}
 
@@ -573,6 +609,10 @@ enum class BridgedMemoryBehavior {
 struct BridgedLocation {
   uint64_t storage[3];
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedLocation() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedLocation(const swift::SILDebugLocation &loc) {
     *reinterpret_cast<swift::SILDebugLocation *>(&storage) = loc;
@@ -804,6 +844,10 @@ struct BridgedTypeArray {
 struct BridgedSILTypeArray {
   BridgedArrayRef typeArray;
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  BridgedSILTypeArray() {}
+
 #ifdef USED_IN_CPP_SOURCE
   BridgedSILTypeArray(llvm::ArrayRef<swift::SILType> silTypes)
       : typeArray(silTypes) {}
@@ -826,6 +870,10 @@ struct BridgedGenericSpecializationInformation {
 struct OptionalBridgedSILDebugVariable {
   uint64_t storage[16];
 
+  // Ensure that this struct value type will be indirectly returned on
+  // Windows ARM64
+  OptionalBridgedSILDebugVariable() {}
+
 #ifdef USED_IN_CPP_SOURCE
   using OptionalSILDebugVariable = std::optional<swift::SILDebugVariable>;
 

include/swift/SILOptimizer/OptimizerBridging.h

@@ -94,6 +94,10 @@ struct BridgedCalleeAnalysis {
   struct CalleeList {
     uint64_t storage[3];
 
+    // Ensure that this struct value type will be indirectly returned on
+    // Windows ARM64
+    CalleeList() {}
+
 #ifdef USED_IN_CPP_SOURCE
     CalleeList(swift::CalleeList list) {
       *reinterpret_cast<swift::CalleeList *>(&storage) = list;