unwrap (reshape) singleton terminal symbols correctly

src/cfgrammar.c

@@ -37,6 +37,15 @@ static void collect_nts(HCFGrammar *grammar, HCFChoice *symbol);
 static void collect_geneps(HCFGrammar *grammar);
 
 
+static const HParsedToken *h_act_first(const HParseResult *p)
+{
+  assert(p->ast);
+  assert(p->ast->token_type == TT_SEQUENCE);
+  assert(p->ast->seq->used > 0);
+
+  return p->ast->seq->elements[0];
+}
+
 /* Convert 'parser' into CFG representation by desugaring and compiling the set
  * of nonterminals.
  * A NULL return means we are unable to represent the parser as a CFG.
@@ -63,6 +72,7 @@ HCFGrammar *h_cfgrammar(HAllocator* mm__, const HParser *parser)
     nt->seq[0]->items[0] = desugared;
     nt->seq[0]->items[1] = NULL;
     nt->seq[1] = NULL;
+    nt->reshape = h_act_first;
     h_hashset_put(g->nts, nt);
     g->start = nt;
   } else {