Still broken, but all desugaring functions stubbed out.

src/parsers/not.c

@@ -10,10 +10,16 @@ static HParseResult* parse_not(void* env, HParseState* state) {
   }
 }
 
+static const HCFChoice* desugar_not(HAllocator *mm__, void *env) {
+  assert_message(0, "Not context-free, can't be desugared");
+  return NULL;
+}
+
 static const HParserVtable not_vt = {
   .parse = parse_not,
   .isValidRegular = h_false,  /* see and.c for why */
   .isValidCF = h_false,       /* also see and.c for why */
+  .desugar = desugar_not,
 };
 
 const HParser* h_not(const HParser* p) {