PyPy uses a tracing JIT, so it observes the general matching algorithm for a few iterations and then emits code that implements what the general algorithm actua

PyPy uses a tracing JIT, so it observes the general matching algorithm for a few iterations and then emits code that implements what the general algorithm actually did, i.e. the specific matching steps for that specific regex. JITting a regex isn't really the same thing as your Rust native regexes; for example, if somebody wrote a regex library with a JIT and linked it to a C program, I woudln't count it. However, in PyPy's case regexes are exactly as native as the rest of the codebase rather than being a nested VM, so in that sense they're 'native'.