@@ 84,7 84,15 @@ namespace {
 			subst.strbeg = label; subst.strend = nullptr;
 			subst.children.resize(children.size(), lithe::node(deleted));
 			size_t i(0);
-			for (auto &c : children) std::swap(subst[i++], *c);
+			for (auto& c : children) {
+				if (subst.src_begin == nullptr || subst.src_begin > c->src_begin) {
+					subst.src_begin = c->src_begin;
+				}
+				if (subst.src_end == nullptr || subst.src_end < c->src_end) {
+					subst.src_end = c->src_end;
+				}
+				std::swap(subst[i++], *c);
+			}
 			std::swap(*dest, subst);
 		}
 	};

          
@@ 100,6 108,8 @@ namespace {
 				lithe::node defn;
 				defn.strbeg = tag::defn;
 				defn.strend = nullptr;
+				defn.src_begin = i->src_begin;
+				defn.src_end = next->src_end;
 				defn.children.emplace_back(*i);
 				defn.children.emplace_back(*next);
 				*i = defn;

          
@@ 245,7 255,14 @@ namespace lithe {
 					"docstring", I(T(";") << O(characters("space","\t "))) << (upto_eol | T("\n")), 
 				[](const lithe::node& n) {
 					if (docstrings().size()) {
-						docstrings().top().children.emplace_back(n);
+						auto& t{ docstrings().top() };
+						if (t.src_begin == nullptr || t.src_begin > n.src_begin) {
+							t.src_begin = n.src_begin;
+						}
+						if (t.src_end == nullptr || t.src_end < n.src_end) {
+							t.src_end = n.src_end;
+						}
+						t.children.emplace_back(n);
 					}
 					return n;
 				});

          

@@ 146,13 146,13 @@ namespace lithe {
 			node complex_seq(cursor& current, cursor limit, node result, size_t i) const {
 				for (;i < sequence.size();++i) {
 					node tmp = (*sequence[i])(current, limit);
-					LITHE_EXTENT_END(result,current);
 					if (tmp.is_error()) {
 						if (tmp.is_fatal()) return tmp;
 						else return node::error(this, current, tmp);
 					}
 					flatten_to(result.children, tmp);
 				}
+				LITHE_EXTENT_END(result, current);
 				return result;
 			}
 

          
@@ 279,6 279,7 @@ namespace lithe {
 					std::clog << indent::current() << "% Matched [" << tag << "]!\n";
 				}
 #endif
+				assert(c.is_error() || (c.src_begin && c.src_end));
 				if (!insert) return c;
 				if (c.strbeg) {
 					node tmp;

          
@@ 663,10 664,14 @@ namespace lithe {
 			custom(const char *name, rule r, std::function<node(node)> process):wrapper(r, name),process(process) {
 			}
 
-			node operator()(cursor& begin, cursor end) const override {
-				auto tmp = wrapper::operator()(begin, end);
+			node operator()(cursor& cur, cursor end) const override {
+				auto b = cur;
+				auto tmp = wrapper::operator()(cur, end);
 				if (tmp.is_error()) return tmp;
-				else return process(std::move(tmp));
+				assert(tmp.src_begin && tmp.src_end);
+				auto tmp2 = process(std::move(tmp));
+				assert(tmp2.is_error() || (tmp2.src_begin && tmp2.src_end));
+				return tmp2;
 			}
 		};