#![feature(core_intrinsics, rustc_attrs)] use std::intrinsics::rustc_peek; #[rustc_mir(rustc_peek_liveness, stop_after_dataflow)] fn foo() -> Option { let mut x = None; // `x` is live here since it is used in the next statement... rustc_peek(x); dbg!(x); // But not here, since it is overwritten below rustc_peek(x); //~ ERROR rustc_peek: bit not set x = Some(4); x } fn main() {}