message: Also disable generating underlying value to symbol conversion declaration when there is an enumerant without explicit value
diff: @@ -211,9 +211,13 @@ static void emitEnumDecl(const Record &enumDef, raw_ostream &os) {
  emitEnumClass(enumDef, enumName, underlyingType, description, enumerants, os);
  // Emit coversion function declarations
  + if (llvm::all_of(enumerants, [](EnumAttrCase enumerant) {
  + return enumerant.getValue() >= 0;
  + })) {
  os << formatv(
  "llvm::Optional<{0}> {1}({2});\n", enumName, underlyingToSymFnName,
  underlyingType.empty() ? std::string("unsigned") : underlyingType);
  + }
  os << formatv("llvm::StringRef {1}({0});\n", enumName, symToStrFnName);
  os << formatv("llvm::Optional<{0}> {1}(llvm::StringRef);\n", enumName,
  strToSymFnName);
  