The Nim compiler used ropes internally for years, until recently[0] because removing them reduced memory consumption and decreased compile times, so ymmv
This is a big tell that maybe we don't want to know exactly the type, but to have way to let the compiler/benchmarks to pick the best performing data structure for the task at hand, but I think that on most programming languages neither the language nor the tooling help you too much here.*
*Saying this mostly with the intent of being proved wrong ;) kxcd://386
[0]https://github.com/nim-lang/Nim/pull/20433