From 4e86e5eedc684453fe0af6eca2ebdbff33db012c Mon Sep 17 00:00:00 2001
From: Eli Friedman <efriedma@quicinc.com>
Date: Sat, 11 Apr 2020 14:53:09 -0700
Subject: [PATCH] [DenseMap] Add assertion that end() iterator isn't
 derefenced.

This would have saved me some time this morning.
---
 llvm/include/llvm/ADT/DenseMap.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/llvm/include/llvm/ADT/DenseMap.h b/llvm/include/llvm/ADT/DenseMap.h
index b73afae..8d83f7e 100644
--- a/llvm/include/llvm/ADT/DenseMap.h
+++ b/llvm/include/llvm/ADT/DenseMap.h
@@ -1201,12 +1201,14 @@ public:
 
   reference operator*() const {
     assert(isHandleInSync() && "invalid iterator access!");
+    assert(Ptr != End && "dereferencing end() iterator");
     if (shouldReverseIterate<KeyT>())
       return Ptr[-1];
     return *Ptr;
   }
   pointer operator->() const {
     assert(isHandleInSync() && "invalid iterator access!");
+    assert(Ptr != End && "dereferencing end() iterator");
     if (shouldReverseIterate<KeyT>())
       return &(Ptr[-1]);
     return Ptr;
@@ -1229,6 +1231,7 @@ public:
 
   inline DenseMapIterator& operator++() {  // Preincrement
     assert(isHandleInSync() && "invalid iterator access!");
+    assert(Ptr != End && "incrementing end() iterator");
     if (shouldReverseIterate<KeyT>()) {
       --Ptr;
       RetreatPastEmptyBuckets();
-- 
2.7.4