add comment re WouldEvenConsiderFormatting

Author: kastiglione

lldb/source/Plugins/Language/Swift/SwiftOptionSet.cpp

@@ -168,6 +168,8 @@ bool lldb_private::formatters::swift::SwiftOptionSetSummaryProvider::
     for (auto val_name : *m_cases) {
       llvm::APInt case_value = val_name.first;
       // Print single valued sets without using enclosing brackets.
+      // `WouldEvenConsiderFormatting` can't opt out early because it
+      // has only the type, but needs the value for this case.
       if (case_value == value) {
         ss << '.' << val_name.second;
         dest.assign(ss.GetData());