[async-iteration] implement Async-from-Sync Iterator

src/ast/ast-types.cc

Index: src/ast/ast-types.cc
diff --git a/src/ast/ast-types.cc b/src/ast/ast-types.cc
index c5cdc8701fce5fc39b90155f18263153a625c7d9..6d2b638d3d6ac074dd9a04ffcf419f9da7c1696c 100644
--- a/src/ast/ast-types.cc
+++ b/src/ast/ast-types.cc
@@ -220,6 +220,7 @@ AstType::bitset AstBitsetType::Lub(i::Map* map) {
     case JS_SET_ITERATOR_TYPE:
     case JS_MAP_ITERATOR_TYPE:
     case JS_STRING_ITERATOR_TYPE:
+    case JS_ASYNC_FROM_SYNC_ITERATOR_TYPE:
 
     case JS_TYPED_ARRAY_KEY_ITERATOR_TYPE:
     case JS_FAST_ARRAY_KEY_ITERATOR_TYPE: