Adds backward to REPL for better error logging.

repl/main.cpp

@@ -90,6 +90,7 @@ void ParseAndUpdate(const std::vector<std::u8string> lines, WINDOW* diagnosticsW
     wrefresh(parsedWindow);
 
     UpdateScriptWithParseInfo(inputWindow, script, diag, firstToken);
+    delete parsedResult;
 }
 
 int main([[maybe_unused]] int argc, [[maybe_unused]] const char* argv[]) {