Type erasure definitely does not give the lowest runtime overhead most of the time, although (a) you can always find special cases and (b) it's great for code s

Type erasure definitely does not give the lowest runtime overhead most of the time, although (a) you can always find special cases and (b) it's great for code size, which sometimes is performance-determining at the system level due to caches. The huge thing that type erasure gives up compared to per-type instantiation is the ability to do per-type inlining and the further optimizations that enables.