> repeated tests of compiling various software packages reveal that the borrow checker is within the noise performance wise.
Out of curiosity, do you have a source for this? The stuff I remember reading on the topic is from back in 2018 where they managed to get the NLL borrow checker to be not much slower than the old borrow checker (https://blog.mozilla.org/nnethercote/2018/11/06/how-to-speed...) -- but that took a concerted effort, and the borrow checker was overall a large enough contributor to compilation time that it was worth spending a bunch of effort optimizing it.
Out of curiosity, do you have a source for this? The stuff I remember reading on the topic is from back in 2018 where they managed to get the NLL borrow checker to be not much slower than the old borrow checker (https://blog.mozilla.org/nnethercote/2018/11/06/how-to-speed...) -- but that took a concerted effort, and the borrow checker was overall a large enough contributor to compilation time that it was worth spending a bunch of effort optimizing it.