From 88c48aa1ea44c514ab6e0fe739968055a1a85f85 Mon Sep 17 00:00:00 2001
From: Sergey Pepyakin <sergei@parity.io>
Date: Tue, 16 Apr 2019 16:35:16 +0200
Subject: [PATCH] Add comment about top_label safety

---
 validation/src/func.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/validation/src/func.rs b/validation/src/func.rs
index a161df0..f157954 100644
--- a/validation/src/func.rs
+++ b/validation/src/func.rs
@@ -1212,8 +1212,14 @@ fn pop_label(
     Ok(())
 }
 
+/// Returns the top most frame from the frame stack.
+///
+/// # Panics
+///
+/// Can be called only when the frame stack is not empty: that is, it is ok to call this function
+/// after initialization of the validation and until the validation reached the latest `End`
+/// operator.
 pub fn top_label(frame_stack: &StackWithLimit<BlockFrame>) -> &BlockFrame {
-    // TODO: This actually isn't safe.
     frame_stack
         .top()
         .expect("this function can't be called with empty frame stack")