Merge from rustc

Author: The Miri Conjob Bot

alloc/src/boxed/thin.rs

@@ -171,7 +171,6 @@ struct WithHeader<H>(NonNull<u8>, PhantomData<H>);
 /// An opaque representation of `WithHeader<H>` to avoid the
 /// projection invariance of `<T as Pointee>::Metadata`.
 #[repr(transparent)]
-#[allow(dead_code)] // Field only used through `WithHeader` type above.
 struct WithOpaqueHeader(NonNull<u8>);
 
 impl WithOpaqueHeader {

alloc/src/vec/in_place_collect.rs

@@ -9,7 +9,7 @@
 //! or [`BinaryHeap<T>`], the adapters guarantee to consume enough items per step to make room
 //! for the results (represented by [`InPlaceIterable`]), provide transitive access to `source`
 //! (via [`SourceIter`]) and thus the underlying allocation.
-//! And finally there are alignment and size constriants to consider, this is currently ensured via
+//! And finally there are alignment and size constraints to consider, this is currently ensured via
 //! const eval instead of trait bounds in the specialized [`SpecFromIter`] implementation.
 //!
 //! [`BinaryHeap<T>`]: crate::collections::BinaryHeap
@@ -168,7 +168,9 @@ const fn in_place_collectible<DEST, SRC>(
     step_merge: Option<NonZeroUsize>,
     step_expand: Option<NonZeroUsize>,
 ) -> bool {
-    if const { SRC::IS_ZST || DEST::IS_ZST || mem::align_of::<SRC>() < mem::align_of::<DEST>() } {
+    // Require matching alignments because an alignment-changing realloc is inefficient on many
+    // system allocators and better implementations would require the unstable Allocator trait.
+    if const { SRC::IS_ZST || DEST::IS_ZST || mem::align_of::<SRC>() != mem::align_of::<DEST>() } {
         return false;
     }
 
@@ -188,7 +190,8 @@ const fn in_place_collectible<DEST, SRC>(
 
 const fn needs_realloc<SRC, DEST>(src_cap: usize, dst_cap: usize) -> bool {
     if const { mem::align_of::<SRC>() != mem::align_of::<DEST>() } {
-        return src_cap > 0;
+        // FIXME: use unreachable! once that works in const
+        panic!("in_place_collectible() prevents this");
     }
 
     // If src type size is an integer multiple of the destination type size then
@@ -276,8 +279,8 @@ where
         let dst_guard = InPlaceDstBufDrop { ptr: dst_buf, len, cap: dst_cap };
         src.forget_allocation_drop_remaining();
 
-        // Adjust the allocation if the alignment didn't match or the source had a capacity in bytes
-        // that wasn't a multiple of the destination type size.
+        // Adjust the allocation if the source had a capacity in bytes that wasn't a multiple
+        // of the destination type size.
         // Since the discrepancy should generally be small this should only result in some
         // bookkeeping updates and no memmove.
         if needs_realloc::<I::Src, T>(src_cap, dst_cap) {
@@ -290,7 +293,7 @@ where
                 let src_size = mem::size_of::<I::Src>().unchecked_mul(src_cap);
                 let old_layout = Layout::from_size_align_unchecked(src_size, src_align);
 
-                // The must be equal or smaller for in-place iteration to be possible
+                // The allocation must be equal or smaller for in-place iteration to be possible
                 // therefore the new layout must be ≤ the old one and therefore valid.
                 let dst_align = mem::align_of::<T>();
                 let dst_size = mem::size_of::<T>().unchecked_mul(dst_cap);

alloc/src/vec/mod.rs

@@ -358,7 +358,7 @@ mod spec_extend;
 ///
 /// `vec![x; n]`, `vec![a, b, c, d]`, and
 /// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec`
-/// with exactly the requested capacity. If <code>[len] == [capacity]</code>,
+/// with at least the requested capacity. If <code>[len] == [capacity]</code>,
 /// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to
 /// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements.
 ///
@@ -1023,8 +1023,11 @@ impl<T, A: Allocator> Vec<T, A> {
 
     /// Shrinks the capacity of the vector as much as possible.
     ///
-    /// It will drop down as close as possible to the length but the allocator
-    /// may still inform the vector that there is space for a few more elements.
+    /// The behavior of this method depends on the allocator, which may either shrink the vector
+    /// in-place or reallocate. The resulting vector might still have some excess capacity, just as
+    /// is the case for [`with_capacity`]. See [`Allocator::shrink`] for more details.
+    ///
+    /// [`with_capacity`]: Vec::with_capacity
     ///
     /// # Examples
     ///
@@ -1074,10 +1077,10 @@ impl<T, A: Allocator> Vec<T, A> {
 
     /// Converts the vector into [`Box<[T]>`][owned slice].
     ///
-    /// If the vector has excess capacity, its items will be moved into a
-    /// newly-allocated buffer with exactly the right capacity.
+    /// Before doing the conversion, this method discards excess capacity like [`shrink_to_fit`].
     ///
     /// [owned slice]: Box
+    /// [`shrink_to_fit`]: Vec::shrink_to_fit
     ///
     /// # Examples
     ///
@@ -3290,8 +3293,10 @@ impl<T, A: Allocator> From<Box<[T], A>> for Vec<T, A> {
 impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> {
     /// Convert a vector into a boxed slice.
     ///
-    /// If `v` has excess capacity, its items will be moved into a
-    /// newly-allocated buffer with exactly the right capacity.
+    /// Before doing the conversion, this method discards excess capacity like [`Vec::shrink_to_fit`].
+    ///
+    /// [owned slice]: Box
+    /// [`Vec::shrink_to_fit`]: Vec::shrink_to_fit
     ///
     /// # Examples
     ///

alloc/src/vec/spec_from_iter.rs

@@ -13,13 +13,13 @@ use super::{IntoIter, SpecExtend, SpecFromIterNested, Vec};
 /// +-+-----------+
 ///   |
 ///   v
-/// +-+-------------------------------+  +---------------------+
-/// |SpecFromIter                  +---->+SpecFromIterNested   |
-/// |where I:                      |  |  |where I:             |
-/// |  Iterator (default)----------+  |  |  Iterator (default) |
-/// |  vec::IntoIter               |  |  |  TrustedLen         |
-/// |  SourceIterMarker---fallback-+  |  +---------------------+
-/// +---------------------------------+
+/// +-+---------------------------------+  +---------------------+
+/// |SpecFromIter                    +---->+SpecFromIterNested   |
+/// |where I:                        |  |  |where I:             |
+/// |  Iterator (default)------------+  |  |  Iterator (default) |
+/// |  vec::IntoIter                 |  |  |  TrustedLen         |
+/// |  InPlaceCollect--(fallback to)-+  |  +---------------------+
+/// +-----------------------------------+
 /// ```
 pub(super) trait SpecFromIter<T, I> {
     fn from_iter(iter: I) -> Self;

core/benches/ascii.rs

@@ -63,6 +63,7 @@ macro_rules! benches {
     }
 }
 
+use std::fmt::Write;
 use test::black_box;
 use test::Bencher;
 
@@ -351,3 +352,30 @@ static ASCII_CHARACTER_CLASS: [AsciiCharacterClass; 256] = [
     N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N,
     N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N,
 ];
+
+const ASCII_PATH: &[u8] = b"home/kyubey/rust/build/x86_64-unknown-linux-gnu/stage0/lib:/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0-tools/release/deps";
+const RUST_INCANTATION: &[u8] = br#"AR_x86_64_unknown_linux_gnu="ar" CARGO_INCREMENTAL="0" CARGO_PROFILE_RELEASE_DEBUG="1" CARGO_PROFILE_RELEASE_DEBUG_ASSERTIONS="false" CARGO_PROFILE_RELEASE_OVERFLOW_CHECKS="false" CARGO_TARGET_DIR="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0-std" CC_x86_64_unknown_linux_gnu="cc" CFG_COMPILER_HOST_TRIPLE="x86_64-unknown-linux-gnu" CFG_RELEASE_CHANNEL="dev" CFLAGS_x86_64_unknown_linux_gnu="-ffunction-sections -fdata-sections -fPIC -m64" CXXFLAGS_x86_64_unknown_linux_gnu="-ffunction-sections -fdata-sections -fPIC -m64" CXX_x86_64_unknown_linux_gnu="c++" LD_LIBRARY_PATH="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0-sysroot/lib/rustlib/x86_64-unknown-linux-gnu/lib" LIBC_CHECK_CFG="1" RANLIB_x86_64_unknown_linux_gnu="ar s" REAL_LIBRARY_PATH_VAR="LD_LIBRARY_PATH" RUSTBUILD_NATIVE_DIR="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/native" RUSTC="/home/kyubey/workspace/rust/build/bootstrap/debug/rustc" RUSTC_BOOTSTRAP="1" RUSTC_BREAK_ON_ICE="1" RUSTC_ERROR_METADATA_DST="/home/kyubey/workspace/rust/build/tmp/extended-error-metadata" RUSTC_FORCE_UNSTABLE="1" RUSTC_HOST_FUSE_LD_LLD="1" RUSTC_INSTALL_BINDIR="bin" RUSTC_LIBDIR="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0/lib" RUSTC_LINT_FLAGS="-Wrust_2018_idioms -Wunused_lifetimes -Wsemicolon_in_expressions_from_macros" RUSTC_REAL="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0/bin/rustc" RUSTC_SNAPSHOT="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0/bin/rustc" RUSTC_SNAPSHOT_LIBDIR="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0/lib" RUSTC_STAGE="0" RUSTC_SYSROOT="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0-sysroot" RUSTC_VERBOSE="0" RUSTDOC="/home/kyubey/workspace/rust/build/bootstrap/debug/rustdoc" RUSTDOCFLAGS="-C target-cpu=native --cfg=bootstrap -Csymbol-mangling-version=legacy -Zunstable-options -Zunstable-options --check-cfg=values(bootstrap) --check-cfg=values(stdarch_intel_sde) --check-cfg=values(no_fp_fmt_parse) --check-cfg=values(no_global_oom_handling) --check-cfg=values(no_rc) --check-cfg=values(no_sync) --check-cfg=values(freebsd12) --check-cfg=values(freebsd13) --check-cfg=values(backtrace_in_libstd) --check-cfg=values(target_env,\"libnx\") --check-cfg=values(target_arch,\"asmjs\",\"spirv\",\"nvptx\",\"xtensa\") -Clink-arg=-fuse-ld=lld -Clink-arg=-Wl,--threads=1 -Wrustdoc::invalid_codeblock_attributes --crate-version 1.72.0-dev -Zcrate-attr=doc(html_root_url=\"https://doc.rust-lang.org/nightly/\") -Zcrate-attr=warn(rust_2018_idioms)" RUSTDOC_FUSE_LD_LLD="1" RUSTDOC_LIBDIR="/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0/lib" RUSTDOC_REAL="/path/to/nowhere/rustdoc/not/required" RUSTFLAGS="-C target-cpu=native --cfg=bootstrap -Csymbol-mangling-version=legacy -Zunstable-options -Zunstable-options --check-cfg=values(bootstrap) --check-cfg=values(stdarch_intel_sde) --check-cfg=values(no_fp_fmt_parse) --check-cfg=values(no_global_oom_handling) --check-cfg=values(no_rc) --check-cfg=values(no_sync) --check-cfg=values(freebsd12) --check-cfg=values(freebsd13) --check-cfg=values(backtrace_in_libstd) --check-cfg=values(target_env,\"libnx\") --check-cfg=values(target_arch,\"asmjs\",\"spirv\",\"nvptx\",\"xtensa\") -Zmacro-backtrace -Clink-args=-Wl,-z,origin -Clink-args=-Wl,-rpath,$ORIGIN/../lib -Clink-args=-fuse-ld=lld -Csplit-debuginfo=off -Cprefer-dynamic -Zinline-mir -Clto=off -Zcrate-attr=doc(html_root_url=\"https://doc.rust-lang.org/nightly/\")" RUST_COMPILER_RT_ROOT="/home/kyubey/workspace/rust/src/llvm-project/compiler-rt" RUST_TEST_THREADS="48" WINAPI_NO_BUNDLED_LIBRARIES="1" __CARGO_DEFAULT_LIB_METADATA="bootstrapstd" "/home/kyubey/workspace/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "bench" "--target" "x86_64-unknown-linux-gnu" "-Zcheck-cfg=names,values,output" "-Zbinary-dep-depinfo" "-j" "48" "--features" " panic-unwind backtrace compiler-builtins-c" "--manifest-path" "/home/kyubey/workspace/rust/library/sysroot/Cargo.toml" "-p" "core" "--" "bench_ascii_escape_display" "--quiet" "-Z" "unstable-options" "--format" "json""#;
+
+#[bench]
+fn bench_ascii_escape_display_no_escape(b: &mut Bencher) {
+    let mut writer = String::with_capacity(8 * 1024);
+
+    b.iter(move || {
+        writer.clear();
+        let iter = ASCII_PATH.escape_ascii();
+        write!(writer, "{}", iter).unwrap();
+        writer.len()
+    })
+}
+
+#[bench]
+fn bench_ascii_escape_display_mixed(b: &mut Bencher) {
+    let mut writer = String::with_capacity(8 * 1024);
+
+    b.iter(move || {
+        writer.clear();
+        let iter = RUST_INCANTATION.escape_ascii();
+        write!(writer, "{}", iter).unwrap();
+        writer.len()
+    })
+}

core/src/array/mod.rs

@@ -647,7 +647,7 @@ impl<T, const N: usize> [T; N] {
     )]
     #[inline]
     pub fn split_array_ref<const M: usize>(&self) -> (&[T; M], &[T]) {
-        (&self[..]).split_array_ref::<M>()
+        (&self[..]).split_first_chunk::<M>().unwrap()
     }
 
     /// Divides one mutable array reference into two at an index.
@@ -680,7 +680,7 @@ impl<T, const N: usize> [T; N] {
     )]
     #[inline]
     pub fn split_array_mut<const M: usize>(&mut self) -> (&mut [T; M], &mut [T]) {
-        (&mut self[..]).split_array_mut::<M>()
+        (&mut self[..]).split_first_chunk_mut::<M>().unwrap()
     }
 
     /// Divides one array reference into two at an index from the end.
@@ -725,7 +725,7 @@ impl<T, const N: usize> [T; N] {
     )]
     #[inline]
     pub fn rsplit_array_ref<const M: usize>(&self) -> (&[T], &[T; M]) {
-        (&self[..]).rsplit_array_ref::<M>()
+        (&self[..]).split_last_chunk::<M>().unwrap()
     }
 
     /// Divides one mutable array reference into two at an index from the end.
@@ -758,7 +758,7 @@ impl<T, const N: usize> [T; N] {
     )]
     #[inline]
     pub fn rsplit_array_mut<const M: usize>(&mut self) -> (&mut [T], &mut [T; M]) {
-        (&mut self[..]).rsplit_array_mut::<M>()
+        (&mut self[..]).split_last_chunk_mut::<M>().unwrap()
     }
 }
 

core/src/ascii.rs

@@ -96,6 +96,17 @@ pub fn escape_default(c: u8) -> EscapeDefault {
     EscapeDefault(escape::EscapeIterInner::new(data, range))
 }
 
+impl EscapeDefault {
+    pub(crate) fn empty() -> Self {
+        let data = [Char::Null; 4];
+        EscapeDefault(escape::EscapeIterInner::new(data, 0..0))
+    }
+
+    pub(crate) fn as_str(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Iterator for EscapeDefault {
     type Item = u8;

core/src/error.rs

@@ -415,7 +415,7 @@ where
 // Request and its methods
 ///////////////////////////////////////////////////////////////////////////////
 
-/// `Request` supports generic, type-driven access to data. It's use is currently restricted to the
+/// `Request` supports generic, type-driven access to data. Its use is currently restricted to the
 /// standard library in cases where trait authors wish to allow trait implementors to share generic
 /// information across trait boundaries. The motivating and prototypical use case is
 /// `core::error::Error` which would otherwise require a method per concrete type (eg.

core/src/iter/adapters/flatten.rs

@@ -24,6 +24,14 @@ impl<I: Iterator, U: IntoIterator, F: FnMut(I::Item) -> U> FlatMap<I, U, F> {
     pub(in crate::iter) fn new(iter: I, f: F) -> FlatMap<I, U, F> {
         FlatMap { inner: FlattenCompat::new(iter.map(f)) }
     }
+
+    pub(crate) fn into_parts(self) -> (Option<U::IntoIter>, Option<I>, Option<U::IntoIter>) {
+        (
+            self.inner.frontiter,
+            self.inner.iter.into_inner().map(Map::into_inner),
+            self.inner.backiter,
+        )
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]

core/src/iter/adapters/fuse.rs

@@ -24,6 +24,10 @@ impl<I> Fuse<I> {
     pub(in crate::iter) fn new(iter: I) -> Fuse<I> {
         Fuse { iter: Some(iter) }
     }
+
+    pub(crate) fn into_inner(self) -> Option<I> {
+        self.iter
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]