Identify parser functions as conditional
diff --git a/src/expr.rs b/src/expr.rs
index 4ccc14d..809463a 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -2428,6 +2428,9 @@
         /// Parse the body of a block as zero or more statements, possibly
         /// including one trailing expression.
         ///
+        /// *This function is available if Syn is built with the `"parsing"`
+        /// feature.*
+        ///
         /// # Example
         ///
         /// ```