Added an assert.

Author: zahiraam

clang/lib/Parse/ParseOpenMP.cpp

@@ -2886,6 +2886,8 @@ StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective(
     // OMP5.2 Chapter 7.4: If no otherwise clause is specified the effect is as
     // if one was specified without an associated directive variant.
     if (BestIdx == -1 && Idx == 1) {
+      assert(Tok.is(tok::annot_pragma_openmp_end) &&
+             "Expecting the end of the pragma here");
       ConsumeAnnotationToken();
       return StmtEmpty();
     }