Auto merge of rust-lang#76678 - jonas-schievink:rollup-vzl9yhx, r=jonas-schievink

Rollup of 12 pull requests

Successful merges:

 - rust-lang#75559 (unions: test move behavior of non-Copy fields)
 - rust-lang#76441 (Note that parallel-compiler = true causes tests to fail)
 - rust-lang#76527 (Remove internal and unstable MaybeUninit::UNINIT.)
 - rust-lang#76629 (Simplify iter zip struct doc)
 - rust-lang#76640 (Simplify SyncOnceCell's `take` and `drop`.)
 - rust-lang#76646 (Add mailmap entry)
 - rust-lang#76651 (Remove Windows details from Unix and VmWorks symlink() docstrings)
 - rust-lang#76663 (Simplify iter chain struct doc)
 - rust-lang#76665 (slice::from_raw_parts: explicitly mention that data must be initialized)
 - rust-lang#76667 (Fix CI LLVM to work on NixOS out of the box)
 - rust-lang#76668 (Add visualization of rustc span in doc)
 - rust-lang#76677 (note that test_stable_pointers does not reflect a stable guarantee)

Failed merges:

r? `@ghost`

Author: bors

.mailmap

@@ -55,6 +55,9 @@ Chris C Cerami <[email protected]> Chris C Cerami <chrisccer
 Chris Pressey <[email protected]>
 Chris Thorn <[email protected]> Chris Thorn <[email protected]>
 Chris Vittal <[email protected]> Christopher Vittal <[email protected]>
+Christiaan Dirkx <[email protected]> <[email protected]>
+Christiaan Dirkx <[email protected]> CDirkx <[email protected]>
+Christiaan Dirkx <[email protected]> CDirkx <[email protected]>
 Christian Poveda <[email protected]> <[email protected]>
 Christian Poveda <[email protected]> <[email protected]>
 Christian Poveda <[email protected]> <[email protected]>

compiler/rustc_span/src/lib.rs

@@ -544,6 +544,12 @@ impl Span {
     }
 
     /// Returns a `Span` that would enclose both `self` and `end`.
+    ///
+    /// ```text
+    ///     ____             ___
+    ///     self lorem ipsum end
+    ///     ^^^^^^^^^^^^^^^^^^^^
+    /// ```
     pub fn to(self, end: Span) -> Span {
         let span_data = self.data();
         let end_data = end.data();
@@ -567,6 +573,12 @@ impl Span {
     }
 
     /// Returns a `Span` between the end of `self` to the beginning of `end`.
+    ///
+    /// ```text
+    ///     ____             ___
+    ///     self lorem ipsum end
+    ///         ^^^^^^^^^^^^^
+    /// ```
     pub fn between(self, end: Span) -> Span {
         let span = self.data();
         let end = end.data();
@@ -577,7 +589,13 @@ impl Span {
         )
     }
 
-    /// Returns a `Span` between the beginning of `self` to the beginning of `end`.
+    /// Returns a `Span` from the beginning of `self` until the beginning of `end`.
+    ///
+    /// ```text
+    ///     ____             ___
+    ///     self lorem ipsum end
+    ///     ^^^^^^^^^^^^^^^^^
+    /// ```
     pub fn until(self, end: Span) -> Span {
         let span = self.data();
         let end = end.data();

config.toml.example

@@ -393,6 +393,7 @@
 #incremental = false
 
 # Build a multi-threaded rustc
+# FIXME(#75760): Some UI tests fail when this option is enabled.
 #parallel-compiler = false
 
 # The default linker that will be hard-coded into the generated compiler for

library/alloc/src/collections/btree/node.rs

@@ -78,8 +78,8 @@ impl<K, V> LeafNode<K, V> {
         LeafNode {
             // As a general policy, we leave fields uninitialized if they can be, as this should
             // be both slightly faster and easier to track in Valgrind.
-            keys: [MaybeUninit::UNINIT; CAPACITY],
-            vals: [MaybeUninit::UNINIT; CAPACITY],
+            keys: MaybeUninit::uninit_array(),
+            vals: MaybeUninit::uninit_array(),
             parent: ptr::null(),
             parent_idx: MaybeUninit::uninit(),
             len: 0,
@@ -111,7 +111,7 @@ impl<K, V> InternalNode<K, V> {
     /// `len` of 0), there must be one initialized and valid edge. This function does not set up
     /// such an edge.
     unsafe fn new() -> Self {
-        InternalNode { data: unsafe { LeafNode::new() }, edges: [MaybeUninit::UNINIT; 2 * B] }
+        InternalNode { data: unsafe { LeafNode::new() }, edges: MaybeUninit::uninit_array() }
     }
 }
 

library/alloc/src/lib.rs

@@ -100,7 +100,6 @@
 #![feature(fn_traits)]
 #![feature(fundamental)]
 #![feature(inplace_iteration)]
-#![feature(internal_uninit_const)]
 #![feature(lang_items)]
 #![feature(layout_for_ptr)]
 #![feature(libc)]
@@ -135,7 +134,7 @@
 #![feature(unsized_locals)]
 #![feature(allocator_internals)]
 #![feature(slice_partition_dedup)]
-#![feature(maybe_uninit_extra, maybe_uninit_slice)]
+#![feature(maybe_uninit_extra, maybe_uninit_slice, maybe_uninit_uninit_array)]
 #![feature(alloc_layout_extra)]
 #![feature(trusted_random_access)]
 #![feature(try_trait)]

library/alloc/tests/vec.rs

@@ -1511,6 +1511,9 @@ fn test_stable_pointers() {
     // Test that, if we reserved enough space, adding and removing elements does not
     // invalidate references into the vector (such as `v0`).  This test also
     // runs in Miri, which would detect such problems.
+    // Note that this test does *not* constitute a stable guarantee that all these functions do not
+    // reallocate! Only what is explicitly documented at
+    // <https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#guarantees> is stably guaranteed.
     let mut v = Vec::with_capacity(128);
     v.push(13);
 

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

@@ -4,11 +4,8 @@ use crate::usize;
 
 /// An iterator that links two iterators together, in a chain.
 ///
-/// This `struct` is created by the [`chain`] method on [`Iterator`]. See its
-/// documentation for more.
-///
-/// [`chain`]: trait.Iterator.html#method.chain
-/// [`Iterator`]: trait.Iterator.html
+/// This `struct` is created by [`Iterator::chain`]. See its documentation
+/// for more.
 #[derive(Clone, Debug)]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]

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

@@ -8,11 +8,8 @@ use super::super::{
 
 /// An iterator that iterates two other iterators simultaneously.
 ///
-/// This `struct` is created by the [`zip`] method on [`Iterator`]. See its
-/// documentation for more.
-///
-/// [`zip`]: trait.Iterator.html#method.zip
-/// [`Iterator`]: trait.Iterator.html
+/// This `struct` is created by [`Iterator::zip`]. See its documentation
+/// for more.
 #[derive(Clone)]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]

library/core/src/mem/maybe_uninit.rs

@@ -306,14 +306,6 @@ impl<T> MaybeUninit<T> {
         unsafe { MaybeUninit::<[MaybeUninit<T>; LEN]>::uninit().assume_init() }
     }
 
-    /// A promotable constant, equivalent to `uninit()`.
-    #[unstable(
-        feature = "internal_uninit_const",
-        issue = "none",
-        reason = "hack to work around promotability"
-    )]
-    pub const UNINIT: Self = Self::uninit();
-
     /// Creates a new `MaybeUninit<T>` in an uninitialized state, with the memory being
     /// filled with `0` bytes. It depends on `T` whether that already makes for
     /// proper initialization. For example, `MaybeUninit<usize>::zeroed()` is initialized,

library/core/src/slice/mod.rs

@@ -6680,6 +6680,8 @@ unsafe impl<'a, T> TrustedRandomAccess for RChunksExactMut<'a, T> {
 ///       them from other data. You can obtain a pointer that is usable as `data`
 ///       for zero-length slices using [`NonNull::dangling()`].
 ///
+/// * `data` must point to `len` consecutive properly initialized values of type `T`.
+///
 /// * The memory referenced by the returned slice must not be mutated for the duration
 ///   of lifetime `'a`, except inside an `UnsafeCell`.
 ///
@@ -6767,6 +6769,8 @@ pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
 ///       them from other data. You can obtain a pointer that is usable as `data`
 ///       for zero-length slices using [`NonNull::dangling()`].
 ///
+/// * `data` must point to `len` consecutive properly initialized values of type `T`.
+///
 /// * The memory referenced by the returned slice must not be accessed through any other pointer
 ///   (not derived from the return value) for the duration of lifetime `'a`.
 ///   Both read and write accesses are forbidden.