I'd really like to see a careful compiler like Rust have a "fast and loose" mode for the development loop, whereby I swear on my mother's grave that I won't bre

I'd really like to see a careful compiler like Rust have a "fast and loose" mode for the development loop, whereby I swear on my mother's grave that I won't break any rules, and the compiler in turn stops making expensive checks. This would of course be for development only, not for releasing.