C++: Add test with missing flow.

cpp/ql/test/library-tests/dataflow/dataflow-tests/TestBase.qll

@@ -151,6 +151,9 @@ module IRTest {
         or
         call.getTarget().getName() = "indirect_sink" and
         sink.asIndirectExpr() = e
+        or
+        call.getTarget().getName() = "indirect_sink_const_ref" and
+        sink.asIndirectExpr() = e
       )
     }
 

cpp/ql/test/library-tests/dataflow/dataflow-tests/test.cpp

@@ -1073,3 +1073,10 @@ void single_object_in_both_cases(bool b, int x, int y) {
   *p = 0;
   sink(*p); // clean
 }
+
+template<typename T>
+void indirect_sink_const_ref(const T&);
+
+void test_temp_with_conversion_from_materialization() {
+  indirect_sink_const_ref(source()); // $ MISSING: ast,ir
+}