Generate unsafe Default impl for union only in unsafe model

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -3210,12 +3210,19 @@ void Converter::AddCloneTrait(const clang::CXXRecordDecl *decl) {}
 
 void Converter::AddDropTrait(const clang::CXXRecordDecl *decl) {}
 
+void Converter::AddDefaultTraitForUnion(const clang::RecordDecl *decl) {
+  StrCat(std::format("impl Default for {}", GetRecordName(decl)));
+  PushBrace impl_brace(*this);
+  StrCat("fn default() -> Self");
+  PushBrace fn_brace(*this);
+  StrCat("unsafe");
+  PushBrace unsafe_brace(*this);
+  StrCat("std::mem::zeroed()");
+}
+
 void Converter::AddDefaultTrait(const clang::RecordDecl *decl) {
   if (decl->isUnion()) {
-    StrCat(
-        std::format("impl Default for {} {{ fn default() -> Self {{ unsafe {{ "
-                    "std::mem::zeroed() }} }} }}",
-                    GetRecordName(decl)));
+    AddDefaultTraitForUnion(decl);
     return;
   }
   if (RecordDerivesDefault(decl)) {

cpp2rust/converter/converter.h

@@ -445,6 +445,8 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
 
   virtual void AddDefaultTrait(const clang::RecordDecl *decl);
 
+  virtual void AddDefaultTraitForUnion(const clang::RecordDecl *decl);
+
   virtual void AddByteReprTrait(const clang::RecordDecl *decl);
 
   virtual void

cpp2rust/converter/models/converter_refcount.cpp

@@ -465,6 +465,9 @@ void ConverterRefCount::AddDefaultTrait(const clang::RecordDecl *decl) {
   Converter::AddDefaultTrait(decl);
 }
 
+void ConverterRefCount::AddDefaultTraitForUnion(const clang::RecordDecl *decl) {
+}
+
 void ConverterRefCount::AddDropTrait(const clang::CXXRecordDecl *decl) {
   if (!decl->hasUserDeclaredDestructor()) {
     return;

cpp2rust/converter/models/converter_refcount.h

@@ -41,6 +41,8 @@ class ConverterRefCount final : public Converter {
 
   void AddDefaultTrait(const clang::RecordDecl *decl) override;
 
+  void AddDefaultTraitForUnion(const clang::RecordDecl *decl) override;
+
   std::string GetSelfMaybeWithMut(const clang::CXXMethodDecl *decl) override;
 
   bool VisitCXXConstructorDecl(clang::CXXConstructorDecl *decl) override;