Fix lazy removal of unscoped messages also removing still valid msgs

tests/ExtraTests/X06-MixingClearedAndUnclearedMessages.cpp

@@ -0,0 +1,27 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+
+/**\file
+ * Checks that when we use up an unscoped message (e.g. `UNSCOPED_INFO`),
+ * with an assertion, and then add another message later, it will be
+ * properly reported with later failing assertion.
+ *
+ * This needs separate binary to avoid the main test binary's validating
+ * listener, which disables the assertion fast path.
+ */
+
+#include <catch2/catch_test_macros.hpp>
+
+TEST_CASE(
+    "Delayed unscoped message clearing does not catch newly inserted messages",
+    "[messages][unscoped][!shouldfail]" ) {
+    UNSCOPED_INFO( "a" );
+    REQUIRE( true );
+    UNSCOPED_INFO( "b" );
+    REQUIRE( false );
+}