Index: clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h
===================================================================
--- clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h
+++ clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h
@@ -87,7 +87,9 @@
 
 /// An immutable map from CallDescriptions to arbitrary data. Provides a unified
 /// way for checkers to react on function calls.
-template <typename T> class CallDescriptionMap {
+template <typename T = void> class CallDescriptionMap {
+  friend class CallDescriptionMap<void>;
+
   // Some call descriptions aren't easily hashable (eg., the ones with qualified
   // names in which some sections are omitted), so let's put them
   // in a simple vector and use linear lookup.
@@ -118,6 +120,25 @@
   }
 };
 
+template <> class CallDescriptionMap<void> {
+  CallDescriptionMap<bool /*unused*/> Impl = {};
+
+public:
+  CallDescriptionMap(std::initializer_list<CallDescription> &&List) {
+    Impl.LinearMap.reserve(List.size());
+    for (const CallDescription &CD : List)
+      Impl.LinearMap.push_back({CD, true});
+  }
+
+  ~CallDescriptionMap() = default;
+  CallDescriptionMap(const CallDescriptionMap &) = delete;
+  CallDescriptionMap &operator=(const CallDescription &) = delete;
+
+  bool lookup(const CallEvent &Call) const {
+    return static_cast<bool>(Impl.lookup(Call));
+  }
+};
+
 } // namespace ento
 } // namespace clang