Do not return dropped tokens from Lexer.lex_token()

assets/parser.d.erb

@@ -141,6 +141,18 @@ class <%= classname %>
         }
 
         LexedToken lex_token()
+        {
+            for (;;)
+            {
+                LexedToken lt = attempt_lex_token();
+                if (lt.token != TOKEN_DROP)
+                {
+                    return lt;
+                }
+            }
+        }
+
+        private LexedToken attempt_lex_token()
         {
             LexedToken lt = LexedToken(m_input_row, m_input_col, TOKEN_NONE);
             struct LexedTokenState