Those are only advice to the compiler, but importantly `safety` is about run-time error checking. Pushing `speed` higher and dropping `safety` to 0 means that r

Those are only advice to the compiler, but importantly `safety` is about run-time error checking. Pushing `speed` higher and dropping `safety` to 0 means that runtime type checks might be removed for certain things, but it's not required to. Like if you've similarly declared that a variable definitely holds a `fixnum`, it'll believe you whether that turns out to be the right thing in the end or not. But again, it's advice. The compiler could leave those runtime checks in place, too.