I already get fast feedback on my code inlined in my editor, and for most languages it only takes 1-2 seconds after I finish typing to update (much longer for Rust, of course). I've never personally found that those 1-2 seconds are a barrier, since I type way faster than I can think anyway.

By the time I've finished typing and am ready to evaluate what I've written, the error highlighting has already popped up letting me know what's wrong.