diff --git a/includes/ast/__init__.vp b/includes/ast/__init__.vp
index b87234a..4ea601f 100644
--- a/includes/ast/__init__.vp
+++ b/includes/ast/__init__.vp
@@ -96,7 +96,7 @@ def parse(src: str, pool: memhub.MemManager | t.CPtr) -> AST | t.CPtr:
     return tree
 
 
-def parse_expression(src: str, pool: memhub.MemManager | t.CPtr) -> AST | t.CPtr:
+def parse_expression(src: str, pool: memhub.MemManager | t.CPtr) -> Expression | t.CPtr:
     """Parse a single expression, return the Expression node.
 
     Parameters:
@@ -104,7 +104,7 @@ def parse_expression(src: str, pool: memhub.MemManager | t.CPtr) -> AST | t.CPtr
         pool: memhub.MemManager instance, to allocate AST nodes
 
     Returns:
-        Expression node, or None
+        Expression node (包装节点，body 字段为实际表达式), or None
     """
     if src is None or pool is None:
         return None