Do you remeber what was the problem? I have the same problem now and idk what's wrong.

I don't recall anything having a reference to &str in the details of this, but if we want to discuss the details of the task:

Your task is to write a function that takes a string and return a new string with all vowels removed.

It states that you are taking a string, and returning a new string. So modifying the existing string and returning it is not the same as returning a new string, as described in the assignment. If there is a by reference involved in the solution's template, that may be an update to the kata from the time this, and many other solutions were written. But in any event, the details of the task tell you to return a new string, not the one that was sent to the function.

/shrug

I don't see how the string is being passed by reference, as you need to specify by reference in the function parameters, and would change how we access the data within the string. But regex_replace creates an empty result string, and then populates and returns it based on the regex rules against the original string. It is not modifying the original string.

The tests are fine, read the description again:

Each letter of a word scores points according to its position in the alphabet: a = 1, b = 2, c = 3 etc.