support empty tuple ()

src/common/sstream.c

@@ -98,7 +98,10 @@ void c11_sbuf__write_quoted(c11_sbuf* self, c11_sv sv, char quote) {
             case '\r': c11_sbuf__write_cstrn(self, "\\r", 2); break;
             case '\t': c11_sbuf__write_cstrn(self, "\\t", 2); break;
             case '\b': c11_sbuf__write_cstrn(self, "\\b", 2); break;
-            default:
+            default: {
+                int u8bytes = c11__u8_header(c, true);
+                if(u8bytes <= 1) {
+                    // not a valid utf8 char, or ascii
                     if(!isprint(c)) {
                         unsigned char uc = (unsigned char)c;
                         c11_sbuf__write_cstrn(self, "\\x", 2);
@@ -107,6 +110,14 @@ void c11_sbuf__write_quoted(c11_sbuf* self, c11_sv sv, char quote) {
                     } else {
                         c11_sbuf__write_char(self, c);
                     }
+                } else {
+                    for(int j = 0; j < u8bytes; j++) {
+                        c11_sbuf__write_char(self, sv.data[i + j]);
+                    }
+                    i += u8bytes - 1;
+                }
+                break;
+            }
         }
     }
     c11_sbuf__write_char(self, quote);

src/compiler/compiler.c

@@ -1722,6 +1722,11 @@ static Error* exprUnaryOp(Compiler* self) {
 static Error* exprGroup(Compiler* self) {
     Error* err;
     int line = prev()->line;
+    if(match(TK_RPAREN)) {
+        // empty tuple
+        Ctx__s_push(ctx(), (Expr*)TupleExpr__new(line, 0));
+        return NULL;
+    }
     match_newlines();
     check(EXPR_TUPLE(self));  // () is just for change precedence
     match_newlines();