Rollup merge of #111609 - LegionMammal978:internal-unsafe, r=thomcc

Mark internal functions and traits unsafe to reflect preconditions

No semantics are changed in this PR; I only mark some functions and and a trait `unsafe` which already had implicit preconditions. Although it seems somewhat redundant for `numfmt::Part::Copy` to contain a `&[u8]` instead of a `&str`, given that all of its current consumers ultimately expect valid UTF-8. Is the type also intended to work for byte-slice formatting in the future?

1 files changed, 5 insertions, 4 deletions

diff --git a/library/alloc/src/vec/in_place_collect.rs b/library/alloc/src/vec/in_place_collect.rs
index 2f1ee8b0353..5ecd0479971 100644
--- a/library/alloc/src/vec/in_place_collect.rs
+++ b/library/alloc/src/vec/in_place_collect.rs
@@ -178,7 +178,8 @@ where
             )
         };
 
-        let len = SpecInPlaceCollect::collect_in_place(&mut iterator, dst_buf, dst_end);
+        // SAFETY: `dst_buf` and `dst_end` are the start and end of the buffer.
+        let len = unsafe { SpecInPlaceCollect::collect_in_place(&mut iterator, dst_buf, dst_end) };
 
         let src = unsafe { iterator.as_inner().as_into_iter() };
         // check if SourceIter contract was upheld
@@ -239,7 +240,7 @@ trait SpecInPlaceCollect<T, I>: Iterator<Item = T> {
     /// `Iterator::__iterator_get_unchecked` calls with a `TrustedRandomAccessNoCoerce` bound
     /// on `I` which means the caller of this method must take the safety conditions
     /// of that trait into consideration.
-    fn collect_in_place(&mut self, dst: *mut T, end: *const T) -> usize;
+    unsafe fn collect_in_place(&mut self, dst: *mut T, end: *const T) -> usize;
 }
 
 impl<T, I> SpecInPlaceCollect<T, I> for I
@@ -247,7 +248,7 @@ where
     I: Iterator<Item = T>,
 {
     #[inline]
-    default fn collect_in_place(&mut self, dst_buf: *mut T, end: *const T) -> usize {
+    default unsafe fn collect_in_place(&mut self, dst_buf: *mut T, end: *const T) -> usize {
         // use try-fold since
         // - it vectorizes better for some iterator adapters
         // - unlike most internal iteration methods, it only takes a &mut self
@@ -265,7 +266,7 @@ where
     I: Iterator<Item = T> + TrustedRandomAccessNoCoerce,
 {
     #[inline]
-    fn collect_in_place(&mut self, dst_buf: *mut T, end: *const T) -> usize {
+    unsafe fn collect_in_place(&mut self, dst_buf: *mut T, end: *const T) -> usize {
         let len = self.size();
         let mut drop_guard = InPlaceDrop { inner: dst_buf, dst: dst_buf };
         for i in 0..len {