add GetEnumCaseName docstring

Author: kastiglione

lldb/include/lldb/Target/SwiftLanguageRuntime.h

@@ -256,6 +256,8 @@ class SwiftLanguageRuntime : public LanguageRuntime {
   llvm::Optional<unsigned> GetNumChildren(CompilerType type,
                                           ValueObject *valobj);
 
+  /// Determine the enum case name for the \p data value of the enum \p type.
+  /// This is performed using Swift reflection.
   llvm::Optional<std::string> GetEnumCaseName(CompilerType type,
                                               const DataExtractor &data,
                                               ExecutionContext *exe_ctx);