Improve parser error handling

src/main.zig

@@ -67,8 +67,10 @@ fn run(allocator: std.mem.Allocator, bytes: []u8) !void {
         .allocator = alloc,
     };
 
-    const expression = try parse.expression();
-    // std.debug.print("AST: {}", .{expression.*});
-    expr.AstPrint(expression.*);
+    const expression = parse.parse();
+    if (err.hasError) {
+        return;
+    }
+    expr.AstPrint(expression);
     std.debug.print("\n", .{});
 }