Implement LWG issue 2306: match_results::reference should be value_type&, not const value_type&. This is a general move by the LWG to have the reference type of read-only containers be a non-const reference; however, there are no methods that return a non-const reference to a match_result entry, so there's no worries about getting a non-const reference to a constant object.

llvm-svn: 202214
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 16da3240517366168e9d0618eff2d8ce957024df
diff --git a/include/regex b/include/regex
index e121738..26ade48 100644
--- a/include/regex
+++ b/include/regex
@@ -437,7 +437,7 @@
 public:
     typedef sub_match<BidirectionalIterator>                  value_type;
     typedef const value_type&                                 const_reference;
-    typedef const_reference                                   reference;
+    typedef value_type&                                       reference;
     typedef /implementation-defined/                          const_iterator;
     typedef const_iterator                                    iterator;
     typedef typename iterator_traits<BidirectionalIterator>::difference_type difference_type;
@@ -5263,7 +5263,7 @@
 public:
     _BidirectionalIterator __position_start_;
     typedef const value_type&                                 const_reference;
-    typedef const_reference                                   reference;
+    typedef value_type&                                       reference;
     typedef typename __container_type::const_iterator         const_iterator;
     typedef const_iterator                                    iterator;
     typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;