2 files changed, 17 insertions, 10 deletions

diff --git a/src/yuescript/yue_compiler.cpp b/src/yuescript/yue_compiler.cpp
index 4072974..f5436d1 100644
--- a/src/yuescript/yue_compiler.cpp
+++ b/src/yuescript/yue_compiler.cpp
@@ -59,7 +59,7 @@ namespace yue {
 
 typedef std::list<std::string> str_list;
 
-const std::string_view version = "0.15.11"sv;
+const std::string_view version = "0.15.12"sv;
 const std::string_view extension = "yue"sv;
 
 class YueCompilerImpl {
@@ -3769,7 +3769,7 @@ private:
                 if (!_enableReturn.top()) {
                         ast_node* target = returnNode->valueList.get();
                         if (!target) target = returnNode;
-                        throw std::logic_error(_info.errorMessage("illegal return statement here"sv, target));
+                        throw std::logic_error(_info.errorMessage("can not mix use of return and export statements in module scope"sv, target));
                 }
                 if (auto valueList = returnNode->valueList.as<ExpListLow_t>()) {
                         if (valueList->exprs.size() == 1) {
@@ -8008,8 +8008,11 @@ private:
 
         void transformChainAssign(ChainAssign_t* chainAssign, str_list& out) {
                 auto x = chainAssign;
-                str_list temp;
                 auto value = chainAssign->assign->values.front();
+                if (chainAssign->assign->values.size() != 1) {
+                        throw std::logic_error(_info.errorMessage("only one right value expected"sv, value));
+                }
+                str_list temp;
                 bool constVal = false;
                 if (auto simpleVal = simpleSingleValueFrom(value)) {
                         constVal = ast_is<const_value_t, Num_t>(simpleVal->value);
diff --git a/src/yuescript/yue_parser.cpp b/src/yuescript/yue_parser.cpp
index b1f29a9..c8b974f 100644
--- a/src/yuescript/yue_parser.cpp
+++ b/src/yuescript/yue_parser.cpp
@@ -532,17 +532,21 @@ YueParser::YueParser() {
                 return true;
         }) >> (pl::user(Space >> export_default >> Exp, [](const item_t& item) {
                 State* st = reinterpret_cast<State*>(item.user_data);
-                bool isValid = !st->exportDefault && st->exportCount == 1;
+                if (st->exportDefault) {
+                        throw ParserError("export default has already been declared", *item.begin, *item.end);
+                }
+                if (st->exportCount > 1) {
+                        throw ParserError("there are items already been exported", *item.begin, *item.end);
+                }
                 st->exportDefault = true;
-                return isValid;
+                return true;
         })
         | (not_(Space >> export_default) >> pl::user(true_(), [](const item_t& item) {
                 State* st = reinterpret_cast<State*>(item.user_data);
                 if (st->exportDefault && st->exportCount > 1) {
-                        return false;
-                } else {
-                        return true;
+                        throw ParserError("can not export more items when export default has been declared", *item.begin, *item.end);
                 }
+                return true;
         }) >> ExpList >> -Assign)
         | Space >> pl::user(Macro, [](const item_t& item) {
                 State* st = reinterpret_cast<State*>(item.user_data);
@@ -631,7 +635,7 @@ YueParser::YueParser() {
                 ) | arg_table_block;
 
         leading_spaces_error = pl::user(+space_one >> expr('(') >> Exp >> +(sym(',') >> Exp) >> sym(')'), [](const item_t& item) {
-                throw ParserError("write invoke arguments in parentheses without leading spaces or leading spaces without parentheses", *item.begin, *item.end);
+                throw ParserError("write invoke arguments in parentheses without leading spaces or just leading spaces without parentheses", *item.begin, *item.end);
                 return false;
         });
 
@@ -707,7 +711,7 @@ ParseInfo YueParser::parse(std::string_view codes, rule& r) {
                 res.codes = std::make_unique<input>();
                 *(res.codes) = _converter.from_bytes(&codes.front(), &codes.back() + 1);
         } catch (const std::range_error&) {
-                res.error = "Invalid text encoding."sv;
+                res.error = "invalid text encoding"sv;
                 return res;
         }
         error_list errors;