Allow DenseSet::iterators to be conveted to and compared with const_iterator

Summary:
This seemed to be an oversight seeing as DenseMap has these conversions.

This patch does the following:
- Adds a default constructor to the iterators.
- Allows DenseSet::ConstIterators to be copy constructed from DenseSet::Iterators
- Allows mutual comparison between Iterators and ConstIterators.

All of these are available in the DenseMap implementation, so the implementation here is trivial.

Reviewers: dblaikie, dberris

Reviewed By: dberris

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28999

llvm-svn: 292879

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/DenseSetTest.cpp b/llvm/unittests/ADT/DenseSetTest.cpp
index 4d5a82902f0..4b159744eba 100644
--- a/llvm/unittests/ADT/DenseSetTest.cpp
+++ b/llvm/unittests/ADT/DenseSetTest.cpp
@@ -73,6 +73,15 @@ TYPED_TEST(DenseSetTest, InitializerList) {
   EXPECT_EQ(0u, set.count(3));
 }
 
+TYPED_TEST(DenseSetTest, ConstIteratorComparison){
+  TypeParam set({1});
+  const TypeParam &cset = set;
+  EXPECT_EQ(set.begin(), cset.begin());
+  EXPECT_EQ(set.end(), cset.end());
+  EXPECT_NE(set.end(), cset.begin());
+  EXPECT_NE(set.begin(), cset.end());
+}
+
 TYPED_TEST(DenseSetTest, EmptyInitializerList) {
   TypeParam set({});
   EXPECT_EQ(0u, set.size());