From 1b66a799c7ef707d2cd4b325b654e69bf536c30f Mon Sep 17 00:00:00 2001
From: Frank Steffahn <frank.steffahn@stu.uni-kiel.de>
Date: Tue, 1 Jun 2021 02:21:26 +0200
Subject: Remove unsound TrustedRandomAccess implementations

Removes the implementations that depend on the user-definable trait `Copy`.

Only fix regressions to ensure merge in 1.55: Does not modify `vec::IntoIter`.
---
 .../alloc/src/collections/vec_deque/into_iter.rs   | 30 +---------------------
 1 file changed, 1 insertion(+), 29 deletions(-)

(limited to 'library/alloc/src')

diff --git a/library/alloc/src/collections/vec_deque/into_iter.rs b/library/alloc/src/collections/vec_deque/into_iter.rs
index 46a769a722a..612f7e6eb4d 100644
--- a/library/alloc/src/collections/vec_deque/into_iter.rs
+++ b/library/alloc/src/collections/vec_deque/into_iter.rs
@@ -1,5 +1,5 @@
 use core::fmt;
-use core::iter::{FusedIterator, TrustedLen, TrustedRandomAccess};
+use core::iter::{FusedIterator, TrustedLen};
 
 use super::VecDeque;
 
@@ -36,23 +36,6 @@ impl<T> Iterator for IntoIter<T> {
         let len = self.inner.len();
         (len, Some(len))
     }
-
-    #[inline]
-    #[doc(hidden)]
-    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item
-    where
-        Self: TrustedRandomAccess,
-    {
-        // Safety: The TrustedRandomAccess contract requires that callers only pass an index
-        // that is in bounds.
-        // Additionally Self: TrustedRandomAccess is only implemented for T: Copy which means even
-        // multiple repeated reads of the same index would be safe and the
-        // values are !Drop, thus won't suffer from double drops.
-        unsafe {
-            let idx = self.inner.wrap_add(self.inner.tail, idx);
-            self.inner.buffer_read(idx)
-        }
-    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -75,14 +58,3 @@ impl<T> FusedIterator for IntoIter<T> {}
 
 #[unstable(feature = "trusted_len", issue = "37572")]
 unsafe impl<T> TrustedLen for IntoIter<T> {}
-
-#[doc(hidden)]
-#[unstable(feature = "trusted_random_access", issue = "none")]
-// T: Copy as approximation for !Drop since get_unchecked does not update the pointers
-// and thus we can't implement drop-handling
-unsafe impl<T> TrustedRandomAccess for IntoIter<T>
-where
-    T: Copy,
-{
-    const MAY_HAVE_SIDE_EFFECT: bool = false;
-}
-- 
cgit 1.4.1-3-g733a5