Prefer <S>::default instead of default struct literal

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -4048,11 +4048,6 @@ std::string Converter::GetDefaultAsStringFallback(clang::QualType qual_type) {
     return getTypedLiteral("0.0", ToString(qual_type));
   }
 
-  if (auto literal = GetDefaultStructLiteralAsString(qual_type);
-      !literal.empty()) {
-    return literal;
-  }
-
   if (auto record = qual_type->getAsRecordDecl()) {
     if (ctx_.getSourceManager().isInSystemHeader(record->getLocation()) &&
         qual_type.isPODType(ctx_)) {
@@ -4072,21 +4067,6 @@ std::string Converter::GetDefaultAsStringFallback(clang::QualType qual_type) {
   return std::format("<{}>::default()", ToString(qual_type));
 }
 
-std::string
-Converter::GetDefaultStructLiteralAsString(clang::QualType qual_type) {
-  auto *record = qual_type->getAsRecordDecl();
-  if (record == nullptr || record->isUnion()) {
-    return {};
-  }
-  if (auto *cxx = clang::dyn_cast<clang::CXXRecordDecl>(record);
-      cxx && GetUserDefinedDefaultConstructor(cxx)) {
-    return {};
-  }
-  Buffer buf(*this);
-  EmitDefaultStructLiteral(record);
-  return std::move(buf).str();
-}
-
 std::string Converter::ConvertVarDefaultInit(clang::QualType qual_type) {
   return GetDefaultAsString(qual_type);
 }

cpp2rust/converter/converter.h

@@ -552,9 +552,6 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
 
   virtual std::string GetDefaultAsStringFallback(clang::QualType qual_type);
 
-  virtual std::string
-  GetDefaultStructLiteralAsString(clang::QualType qual_type);
-
   virtual std::string ConvertVarDefaultInit(clang::QualType qual_type);
 
   virtual std::string

cpp2rust/converter/models/converter_refcount.cpp

@@ -2187,22 +2187,19 @@ std::string ConverterRefCount::GetDefaultAsString(clang::QualType qual_type) {
 
 std::string
 ConverterRefCount::GetDefaultAsStringFallback(clang::QualType qual_type) {
-  if (qual_type->isReferenceType()) {
-    return Converter::GetDefaultAsStringFallback(qual_type);
-  }
-
-  std::string unboxed;
-  {
-    PushConversionKind push(*this, ConversionKind::Unboxed);
-    unboxed = Converter::GetDefaultAsStringFallback(qual_type);
+  auto canonical = qual_type.getUnqualifiedType().getCanonicalType();
+  if (canonical->isBooleanType() ||
+      (canonical->isIntegerType() && !canonical->isEnumeralType()) ||
+      canonical->isFloatingType()) {
+    std::string unboxed;
+    {
+      PushConversionKind push(*this, ConversionKind::Unboxed);
+      unboxed = Converter::GetDefaultAsStringFallback(qual_type);
+    }
+    return BoxValue(std::move(unboxed));
   }
-  return BoxValue(std::move(unboxed));
-}
 
-std::string
-ConverterRefCount::GetDefaultStructLiteralAsString(clang::QualType qual_type) {
-  PushConversionKind push(*this, ConversionKind::FullRefCount);
-  return Converter::GetDefaultStructLiteralAsString(qual_type);
+  return std::format("<{}>::default()", ToString(qual_type));
 }
 
 std::string

cpp2rust/converter/models/converter_refcount.h

@@ -182,9 +182,6 @@ class ConverterRefCount final : public Converter {
 
   std::string GetDefaultAsStringFallback(clang::QualType qual_type) override;
 
-  std::string
-  GetDefaultStructLiteralAsString(clang::QualType qual_type) override;
-
   std::string ConvertVarDefaultInit(clang::QualType qual_type) override;
 
   std::vector<const char *>