Add key-only projections to immutable C++ maps (#1166)

* Add a simple range adapter.
* Add SortedMap::keys
* Add SortedMap::keys_from
* Add SortedMap::keys_in

1 files changed, 2 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/util/comparator_holder.h b/Firestore/core/src/firebase/firestore/util/comparator_holder.h
index c7f6144..3147117 100644
--- a/Firestore/core/src/firebase/firestore/util/comparator_holder.h
+++ b/Firestore/core/src/firebase/firestore/util/comparator_holder.h
@@ -35,6 +35,7 @@ class ComparatorHolder {
       : comparator_(comparator) {
   }
 
+ public:
   const C& comparator() const noexcept {
     return comparator_;
   }
@@ -50,6 +51,7 @@ class ComparatorHolder<C, true> : private C {
   explicit ComparatorHolder(const C& /* comparator */) noexcept {
   }
 
+ public:
   const C& comparator() const noexcept {
     return *this;
   }