1 files changed, 17 insertions, 10 deletions

diff --git a/src/resp.hpp b/src/resp.hpp
index 02d2746..5eb9ef0 100644
--- a/src/resp.hpp
+++ b/src/resp.hpp
@@ -243,6 +243,7 @@ struct ATuple : public AST {
 		return NULL;
 	}
 
+	void set_fst(const AST* ast) { _fst = ast; }
 	void last(ATuple* ast) { _rst = ast; }
 
 	struct const_iterator {
@@ -336,13 +337,16 @@ list_equals(const ATuple* lhs, const ATuple* rhs)
 	
 	ATuple::const_iterator l = lhs->begin();
 	for (const auto& r : *rhs)
-		if (!(*(*l++) == *r))
+		if (l == lhs->end() || !(*(*l++) == *r))
 			return false;
 	return true;
 }
 
 inline void
 list_append(ATuple* head, const AST* child) {
+	if (!head->fst()) {
+		head->set_fst(child);
+	}
 	for (ATuple* i = head; i; i = const_cast<ATuple*>(i->rst())) {
 		if (!i->rst()) {
 			i->last(new ATuple(child, NULL, child->loc));
@@ -593,26 +597,29 @@ struct Subst : public list<Constraint> {
 		return end();
 	}
 	const AST* apply(const AST* in) const {
-		if (AType::is_expr(in)) {
-			if (in->as_tuple()->empty())
-				return in;
+		if (AType::is_expr(in) && !in->as_tuple()->empty()) {
+			const ATuple* tup = in->as_tuple();
 			List out;
-			const AST* prev = NULL;
-			for (const auto& i : *in->as_tuple()) {
-				if (is_dots(i)) {
-					const_iterator o = find_ellipsis(prev);
+			ATuple::const_iterator next = tup->begin();
+			++next;
+			for (auto i : *tup) {
+				if (next != tup->end() && is_dots(*next)) {
+					const_iterator o = find_ellipsis(i);
 					if (o != end()) {
 						for (auto j : *o->second->as_tuple()) {
 							out.push_back(apply(j));
 						}
 					}
-				} else {
+				} else if (!is_dots(i)) {
 					out.push_back(apply(i));
 				}
-				prev = i;
+				if (next != tup->end())
+					++next;
 			}
 			if (out.head)
 				out.head->loc = in->loc;
+			else
+				out.head = new ATuple(NULL, NULL, in->loc);
 			return out.head;
 		} else {
 			const_iterator i = find(in);