Auto merge of #3363 - RalfJung:rustup, r=RalfJung

Rustup

This should finally work again :)

7 files changed, 59 insertions, 3 deletions

diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs
index 0b142939755..a5d28aa5252 100644
--- a/library/alloc/src/alloc.rs
+++ b/library/alloc/src/alloc.rs
@@ -50,6 +50,8 @@ extern "Rust" {
 #[unstable(feature = "allocator_api", issue = "32838")]
 #[derive(Copy, Clone, Default, Debug)]
 #[cfg(not(test))]
+// the compiler needs to know when a Box uses the global allocator vs a custom one
+#[cfg_attr(not(bootstrap), lang = "global_alloc_ty")]
 pub struct Global;
 
 #[cfg(test)]
@@ -385,6 +387,7 @@ pub const fn handle_alloc_error(layout: Layout) -> ! {
     }
 
     #[cfg(not(feature = "panic_immediate_abort"))]
+    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
     unsafe {
         core::intrinsics::const_eval_select((layout,), ct_error, rt_error)
     }
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index b202d9250d5..2736e5ee6c5 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -2062,6 +2062,9 @@ impl<Args: Tuple, F: AsyncFn<Args> + ?Sized, A: Allocator> AsyncFn<Args> for Box
 #[unstable(feature = "coerce_unsized", issue = "18598")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A> {}
 
+// It is quite crucial that we only allow the `Global` allocator here.
+// Handling arbitrary custom allocators (which can affect the `Box` layout heavily!)
+// would need a lot of codegen and interpreter adjustments.
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U>> for Box<T, Global> {}
 
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index 271ea88fff6..58ffa9710d3 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -180,7 +180,7 @@ pub struct BTreeMap<
     /// `ManuallyDrop` to control drop order (needs to be dropped after all the nodes).
     pub(super) alloc: ManuallyDrop<A>,
     // For dropck; the `Box` avoids making the `Unpin` impl more strict than before
-    _marker: PhantomData<crate::boxed::Box<(K, V)>>,
+    _marker: PhantomData<crate::boxed::Box<(K, V), A>>,
 }
 
 #[stable(feature = "btree_drop", since = "1.7.0")]
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index 084157b97ab..facfc9d208e 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -944,6 +944,21 @@ impl<T, A: Allocator> Rc<T, A> {
     /// is in fact equivalent to <code>[Rc::try_unwrap]\(this).[ok][Result::ok]()</code>.
     /// (Note that the same kind of equivalence does **not** hold true for
     /// [`Arc`](crate::sync::Arc), due to race conditions that do not apply to `Rc`!)
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::rc::Rc;
+    ///
+    /// let x = Rc::new(3);
+    /// assert_eq!(Rc::into_inner(x), Some(3));
+    ///
+    /// let x = Rc::new(4);
+    /// let y = Rc::clone(&x);
+    ///
+    /// assert_eq!(Rc::into_inner(y), None);
+    /// assert_eq!(Rc::into_inner(x), Some(4));
+    /// ```
     #[inline]
     #[stable(feature = "rc_into_inner", since = "1.70.0")]
     pub fn into_inner(this: Self) -> Option<T> {
@@ -1329,6 +1344,7 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
     /// let x_ptr = Rc::into_raw(x);
     /// assert_eq!(unsafe { &*x_ptr }, "hello");
     /// ```
+    #[must_use = "losing the pointer will leak memory"]
     #[stable(feature = "rc_raw", since = "1.17.0")]
     #[rustc_never_returns_null_ptr]
     pub fn into_raw(this: Self) -> *const T {
@@ -2970,7 +2986,7 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
     ///
     /// [`from_raw`]: Weak::from_raw
     /// [`as_ptr`]: Weak::as_ptr
-    #[must_use = "`self` will be dropped if the result is not used"]
+    #[must_use = "losing the pointer will leak memory"]
     #[stable(feature = "weak_into_raw", since = "1.45.0")]
     pub fn into_raw(self) -> *const T {
         let result = self.as_ptr();
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 00f47f5c6e0..80f0f2acc99 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -2719,7 +2719,7 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
     ///
     /// [`from_raw`]: Weak::from_raw
     /// [`as_ptr`]: Weak::as_ptr
-    #[must_use = "`self` will be dropped if the result is not used"]
+    #[must_use = "losing the pointer will leak memory"]
     #[stable(feature = "weak_into_raw", since = "1.45.0")]
     pub fn into_raw(self) -> *const T {
         let result = self.as_ptr();
diff --git a/library/alloc/src/task.rs b/library/alloc/src/task.rs
index b214f4946b1..b40768a52b6 100644
--- a/library/alloc/src/task.rs
+++ b/library/alloc/src/task.rs
@@ -136,6 +136,15 @@ impl<W: Wake + Send + Sync + 'static> From<Arc<W>> for RawWaker {
 #[inline(always)]
 fn raw_waker<W: Wake + Send + Sync + 'static>(waker: Arc<W>) -> RawWaker {
     // Increment the reference count of the arc to clone it.
+    //
+    // The #[inline(always)] is to ensure that raw_waker and clone_waker are
+    // always generated in the same code generation unit as one another, and
+    // therefore that the structurally identical const-promoted RawWakerVTable
+    // within both functions is deduplicated at LLVM IR code generation time.
+    // This allows optimizing Waker::will_wake to a single pointer comparison of
+    // the vtable pointers, rather than comparing all four function pointers
+    // within the vtables.
+    #[inline(always)]
     unsafe fn clone_waker<W: Wake + Send + Sync + 'static>(waker: *const ()) -> RawWaker {
         unsafe { Arc::increment_strong_count(waker as *const W) };
         RawWaker::new(
@@ -304,6 +313,10 @@ impl<W: LocalWake + 'static> From<Rc<W>> for RawWaker {
 #[inline(always)]
 fn local_raw_waker<W: LocalWake + 'static>(waker: Rc<W>) -> RawWaker {
     // Increment the reference count of the Rc to clone it.
+    //
+    // Refer to the comment on raw_waker's clone_waker regarding why this is
+    // always inline.
+    #[inline(always)]
     unsafe fn clone_waker<W: LocalWake + 'static>(waker: *const ()) -> RawWaker {
         unsafe { Rc::increment_strong_count(waker as *const W) };
         RawWaker::new(
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 7bd19875584..c0e934b3b1f 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -1490,6 +1490,12 @@ impl<T, A: Allocator> Vec<T, A> {
     /// vec.insert(4, 5);
     /// assert_eq!(vec, [1, 4, 2, 3, 5]);
     /// ```
+    ///
+    /// # Time complexity
+    ///
+    /// Takes *O*([`Vec::len`]) time. All items after the insertion index must be
+    /// shifted to the right. In the worst case, all elements are shifted when
+    /// the insertion index is 0.
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn insert(&mut self, index: usize, element: T) {
@@ -1913,6 +1919,13 @@ impl<T, A: Allocator> Vec<T, A> {
     /// vec.push(3);
     /// assert_eq!(vec, [1, 2, 3]);
     /// ```
+    ///
+    /// # Time complexity
+    ///
+    /// Takes amortized *O*(1) time. If the vector's length would exceed its
+    /// capacity after the push, *O*(*capacity*) time is taken to copy the
+    /// vector's elements to a larger allocation. This expensive operation is
+    /// offset by the *capacity* *O*(1) insertions it allows.
     #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -1961,6 +1974,10 @@ impl<T, A: Allocator> Vec<T, A> {
     /// }
     /// assert_eq!(from_iter_fallible(0..100), Ok(Vec::from_iter(0..100)));
     /// ```
+    ///
+    /// # Time complexity
+    ///
+    /// Takes *O*(1) time.
     #[inline]
     #[unstable(feature = "vec_push_within_capacity", issue = "100486")]
     pub fn push_within_capacity(&mut self, value: T) -> Result<(), T> {
@@ -1990,6 +2007,10 @@ impl<T, A: Allocator> Vec<T, A> {
     /// assert_eq!(vec.pop(), Some(3));
     /// assert_eq!(vec, [1, 2]);
     /// ```
+    ///
+    /// # Time complexity
+    ///
+    /// Takes *O*(1) time.
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn pop(&mut self) -> Option<T> {