silence new -Wunused-result warnings in test

No functional changes intended.

After https://github.com/llvm/llvm-project/commit/f156b51aecc676a9051136f6f5cb74e37dd574d1,
new -Wunused-result warnings popped up in this test:
https://buildkite.com/llvm-project/upstream-bazel/builds/28320#bc3ec049-af39-4114-b7b8-4cbc180bc09b

diff --git a/llvm/unittests/Support/ExtensibleRTTITest.cpp b/llvm/unittests/Support/ExtensibleRTTITest.cpp
index 4b7fc43..9715d26 100644 (file)
--- a/llvm/unittests/Support/ExtensibleRTTITest.cpp
+++ b/llvm/unittests/Support/ExtensibleRTTITest.cpp
@@ -66,9 +66,9 @@ TEST(ExtensibleRTTI, cast) {
   MyDerivedType D;
   MyBaseType &BD = D;
 
-  cast<MyBaseType>(D);
-  cast<MyBaseType>(BD);
-  cast<MyDerivedType>(BD);
+  (void)cast<MyBaseType>(D);
+  (void)cast<MyBaseType>(BD);
+  (void)cast<MyDerivedType>(BD);
 }
 
 TEST(ExtensibleRTTI, dyn_cast) {