| //@ revisions: allow not_allow | 
 | //@ compile-flags: --crate-type=lib -Cinstrument-coverage  -Zno-profiler-runtime | 
 | //@[allow] check-pass | 
 |  | 
 | #![feature(staged_api, rustc_allow_const_fn_unstable)] | 
 | #![stable(feature = "rust_test", since = "1.0.0")] | 
 |  | 
 | #[stable(feature = "rust_test", since = "1.0.0")] | 
 | #[rustc_const_stable(feature = "rust_test", since = "1.0.0")] | 
 | #[cfg_attr(allow, rustc_allow_const_fn_unstable(const_precise_live_drops))] | 
 | pub const fn unwrap<T>(this: Option<T>) -> T { | 
 | //[not_allow]~^ ERROR: cannot be evaluated | 
 |     match this { | 
 |         Some(x) => x, | 
 |         None => panic!(), | 
 |     } | 
 | } |