[llvm] [llvm-remarkutil] Make invalid states un-representable in the count tool (PR #140829)

[Tobias Stadler via llvm-commits]

================
@@ -250,27 +237,42 @@ Error RemarkCounter::print(StringRef OutputFileName) {
 Expected<Filters> getRemarkFilter() {
   // Create Filter properties.
   std::optional<FilterMatcher> RemarkNameFilter;
+  if (!RemarkNameOpt.empty())
+    RemarkNameFilter = FilterMatcher::createExact(RemarkNameOpt);
+  else if (!RemarkNameOptRE.empty()) {
+    auto FM = FilterMatcher::createRE(RemarkNameOptRE);
+    if (!FM)
+      return FM.takeError();
+    RemarkNameFilter = std::move(*FM);
+  }
+
----------------
tobias-stadler wrote:

We do this a lot, would it be worth adding a `FilterMatcher::createExactOrRE(RemarkNameOpt, RemarkNameOptRE)`? 

https://github.com/llvm/llvm-project/pull/140829