global concat op for strings

ostd/string.hh

@@ -908,6 +908,28 @@ String to_string(std::initializer_list<T> init) {
     return to_string(iter(init));
 }
 
+/* TODO: rvalue ref versions for rhs when we have efficient prepend */
+
+inline String operator+(ConstCharRange lhs, ConstCharRange rhs) {
+    String ret(lhs); ret += rhs; return ret;
+}
+
+inline String operator+(String &&lhs, ConstCharRange rhs) {
+    String ret(move(lhs)); ret += rhs; return ret;
+}
+
+inline String operator+(ConstCharRange lhs, char rhs) {
+    String ret(lhs); ret += rhs; return ret;
+}
+
+inline String operator+(String &&lhs, char rhs) {
+    String ret(move(lhs)); ret += rhs; return ret;
+}
+
+inline String operator+(char lhs, ConstCharRange rhs) {
+    String ret(lhs); ret += rhs; return ret;
+}
+
 template<typename R>
 struct TempCString {
 private: