Fix imports

Author: Fedor Ryabinin

library/core/src/hint.rs

@@ -4,11 +4,9 @@
 //!
 //! Hints may be compile time or runtime.
 
-use safety::{ensures,requires};
+use safety::requires;
 #[cfg(kani)]
 use crate::kani;
-#[allow(unused_imports)]
-use crate::ub_checks::*;
 
 use crate::mem::MaybeUninit;
 use crate::{intrinsics, ub_checks};

library/core/src/iter/adapters/step_by.rs

@@ -1,8 +1,6 @@
-use safety::{ensures,requires};
+use safety::requires;
 #[cfg(kani)]
 use crate::kani;
-#[allow(unused_imports)]
-use crate::ub_checks::*;
 
 use crate::intrinsics;
 use crate::iter::{TrustedLen, TrustedRandomAccess, from_fn};

library/core/src/ops/index_range.rs

@@ -1,8 +1,6 @@
-use safety::{ensures,requires};
+use safety::requires;
 #[cfg(kani)]
 use crate::kani;
-#[allow(unused_imports)]
-use crate::ub_checks::*;
 
 use crate::iter::{FusedIterator, TrustedLen};
 use crate::num::NonZero;

library/std/src/sync/mpmc/context.rs

@@ -1,13 +1,9 @@
 //! Thread-local channel context.
 
-#![feature(ub_checks)]
-use safety::{ensures,requires};
 #[cfg(kani)]
 #[unstable(feature="kani", issue="none")]
 use core::kani;
-#[allow(unused_imports)]
-#[unstable(feature = "ub_checks", issue = "none")]
-use core::ub_checks::*;
+use safety::requires;
 
 use super::select::Selected;
 use super::waker::current_thread_id;