Auto merge of #73265 - mark-i-m:mv-std, r=<try>tmp-nightly

mv std libs to library/

This is the first step in refactoring the directory layout of this repository, with further followup steps planned (but not done yet).

Background: currently, all crates are under src/, without nested src directories and with the unconventional `lib*` prefixes (e.g., `src/libcore/lib.rs`). This directory structures is not idiomatic and makes the `src/` directory rather overwhelming. To improve contributor experience and make things a bit more approachable, we are reorganizing the repo a bit.

In this PR, we move the standard libs (basically anything that is "runtime", as opposed to part of the compiler, build system, or one of the tools, etc). The new layout moves these libraries to a new `library/` directory in the root of the repo. Additionally, we remove the `lib*` prefixes and add nested `src/` directories.  The other crates/tools in this repo are not touched. So in summary:

```
library/<crate>/src/*.rs
src/<all the rest>     // unchanged
```

where `<crate>` is:
- core
- alloc
- std
- test
- proc_macro
- panic_abort
- panic_unwind
- profiler_builtins
- term
- unwind
- rtstartup
- backtrace
- rustc-std-workspace-*

There was a lot of discussion about this and a few rounds of compiler team approvals, FCPs, MCPs, and nominations. The original MCP is https://github.com/rust-lang/compiler-team/issues/298. The final approval of the compiler team was given here: https://github.com/rust-lang/rust/pull/73265#issuecomment-659498446.

The name `library` was chosen to complement a later move of the compiler crates to a `compiler/` directory. There was a lot of discussion around adding the nested `src/` directories. Note that this does increase the nesting depth (plausibly important for manual traversal of the tree, e.g., through GitHub's UI or `cd`), but this is deemed to be better as it fits the standard layout of Rust crates throughout most of the ecosystem, though there is some debate about how much this should apply to multi-crate projects. Overall, there seem to be more people in favor of nested `src/` than against.

After this PR, there are no dependencies out of the `library/` directory except on the `build_helper` (or crates.io crates).

2 files changed, 0 insertions, 602 deletions

diff --git a/src/libcore/array/iter.rs b/src/libcore/array/iter.rs
deleted file mode 100644
index 174f7e26efb..00000000000
--- a/src/libcore/array/iter.rs
+++ /dev/null
@@ -1,236 +0,0 @@
-//! Defines the `IntoIter` owned iterator for arrays.
-
-use crate::{
-    fmt,
-    iter::{ExactSizeIterator, FusedIterator, TrustedLen},
-    mem::{self, MaybeUninit},
-    ops::Range,
-    ptr,
-};
-
-/// A by-value [array] iterator.
-///
-/// [array]: ../../std/primitive.array.html
-#[unstable(feature = "array_value_iter", issue = "65798")]
-pub struct IntoIter<T, const N: usize> {
-    /// This is the array we are iterating over.
-    ///
-    /// Elements with index `i` where `alive.start <= i < alive.end` have not
-    /// been yielded yet and are valid array entries. Elements with indices `i
-    /// < alive.start` or `i >= alive.end` have been yielded already and must
-    /// not be accessed anymore! Those dead elements might even be in a
-    /// completely uninitialized state!
-    ///
-    /// So the invariants are:
-    /// - `data[alive]` is alive (i.e. contains valid elements)
-    /// - `data[..alive.start]` and `data[alive.end..]` are dead (i.e. the
-    ///   elements were already read and must not be touched anymore!)
-    data: [MaybeUninit<T>; N],
-
-    /// The elements in `data` that have not been yielded yet.
-    ///
-    /// Invariants:
-    /// - `alive.start <= alive.end`
-    /// - `alive.end <= N`
-    alive: Range<usize>,
-}
-
-impl<T, const N: usize> IntoIter<T, N> {
-    /// Creates a new iterator over the given `array`.
-    ///
-    /// *Note*: this method might never get stabilized and/or removed in the
-    /// future as there will likely be another, preferred way of obtaining this
-    /// iterator (either via `IntoIterator` for arrays or via another way).
-    #[unstable(feature = "array_value_iter", issue = "65798")]
-    pub fn new(array: [T; N]) -> Self {
-        // SAFETY: The transmute here is actually safe. The docs of `MaybeUninit`
-        // promise:
-        //
-        // > `MaybeUninit<T>` is guaranteed to have the same size and alignment
-        // > as `T`.
-        //
-        // The docs even show a transmute from an array of `MaybeUninit<T>` to
-        // an array of `T`.
-        //
-        // With that, this initialization satisfies the invariants.
-
-        // FIXME(LukasKalbertodt): actually use `mem::transmute` here, once it
-        // works with const generics:
-        //     `mem::transmute::<[T; {N}], [MaybeUninit<T>; {N}]>(array)`
-        //
-        // Until then, we do it manually here. We first create a bitwise copy
-        // but cast the pointer so that it is treated as a different type. Then
-        // we forget `array` so that it is not dropped.
-        let data = unsafe {
-            let data = ptr::read(&array as *const [T; N] as *const [MaybeUninit<T>; N]);
-            mem::forget(array);
-            data
-        };
-
-        Self { data, alive: 0..N }
-    }
-
-    /// Returns an immutable slice of all elements that have not been yielded
-    /// yet.
-    fn as_slice(&self) -> &[T] {
-        let slice = &self.data[self.alive.clone()];
-        // SAFETY: This transmute is safe. As mentioned in `new`, `MaybeUninit` retains
-        // the size and alignment of `T`. Furthermore, we know that all
-        // elements within `alive` are properly initialized.
-        unsafe { mem::transmute::<&[MaybeUninit<T>], &[T]>(slice) }
-    }
-
-    /// Returns a mutable slice of all elements that have not been yielded yet.
-    fn as_mut_slice(&mut self) -> &mut [T] {
-        // This transmute is safe, same as in `as_slice` above.
-        let slice = &mut self.data[self.alive.clone()];
-        // SAFETY: This transmute is safe. As mentioned in `new`, `MaybeUninit` retains
-        // the size and alignment of `T`. Furthermore, we know that all
-        // elements within `alive` are properly initialized.
-        unsafe { mem::transmute::<&mut [MaybeUninit<T>], &mut [T]>(slice) }
-    }
-}
-
-#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
-impl<T, const N: usize> Iterator for IntoIter<T, N> {
-    type Item = T;
-    fn next(&mut self) -> Option<Self::Item> {
-        if self.alive.start == self.alive.end {
-            return None;
-        }
-
-        // Bump start index.
-        //
-        // From the check above we know that `alive.start != alive.end`.
-        // Combine this with the invariant `alive.start <= alive.end`, we know
-        // that `alive.start < alive.end`. Increasing `alive.start` by 1
-        // maintains the invariant regarding `alive`. However, due to this
-        // change, for a short time, the alive zone is not `data[alive]`
-        // anymore, but `data[idx..alive.end]`.
-        let idx = self.alive.start;
-        self.alive.start += 1;
-
-        // Read the element from the array.
-        // SAFETY: This is safe: `idx` is an index
-        // into the "alive" region of the array. Reading this element means
-        // that `data[idx]` is regarded as dead now (i.e. do not touch). As
-        // `idx` was the start of the alive-zone, the alive zone is now
-        // `data[alive]` again, restoring all invariants.
-        let out = unsafe { self.data.get_unchecked(idx).read() };
-
-        Some(out)
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        let len = self.len();
-        (len, Some(len))
-    }
-
-    fn count(self) -> usize {
-        self.len()
-    }
-
-    fn last(mut self) -> Option<Self::Item> {
-        self.next_back()
-    }
-}
-
-#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
-impl<T, const N: usize> DoubleEndedIterator for IntoIter<T, N> {
-    fn next_back(&mut self) -> Option<Self::Item> {
-        if self.alive.start == self.alive.end {
-            return None;
-        }
-
-        // Decrease end index.
-        //
-        // From the check above we know that `alive.start != alive.end`.
-        // Combine this with the invariant `alive.start <= alive.end`, we know
-        // that `alive.start < alive.end`. As `alive.start` cannot be negative,
-        // `alive.end` is at least 1, meaning that we can safely decrement it
-        // by one. This also maintains the invariant `alive.start <=
-        // alive.end`. However, due to this change, for a short time, the alive
-        // zone is not `data[alive]` anymore, but `data[alive.start..alive.end
-        // + 1]`.
-        self.alive.end -= 1;
-
-        // Read the element from the array.
-        // SAFETY: This is safe: `alive.end` is an
-        // index into the "alive" region of the array. Compare the previous
-        // comment that states that the alive region is
-        // `data[alive.start..alive.end + 1]`. Reading this element means that
-        // `data[alive.end]` is regarded as dead now (i.e. do not touch). As
-        // `alive.end` was the end of the alive-zone, the alive zone is now
-        // `data[alive]` again, restoring all invariants.
-        let out = unsafe { self.data.get_unchecked(self.alive.end).read() };
-
-        Some(out)
-    }
-}
-
-#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
-impl<T, const N: usize> Drop for IntoIter<T, N> {
-    fn drop(&mut self) {
-        // SAFETY: This is safe: `as_mut_slice` returns exactly the sub-slice
-        // of elements that have not been moved out yet and that remain
-        // to be dropped.
-        unsafe { ptr::drop_in_place(self.as_mut_slice()) }
-    }
-}
-
-#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
-impl<T, const N: usize> ExactSizeIterator for IntoIter<T, N> {
-    fn len(&self) -> usize {
-        // Will never underflow due to the invariant `alive.start <=
-        // alive.end`.
-        self.alive.end - self.alive.start
-    }
-    fn is_empty(&self) -> bool {
-        self.alive.is_empty()
-    }
-}
-
-#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
-impl<T, const N: usize> FusedIterator for IntoIter<T, N> {}
-
-// The iterator indeed reports the correct length. The number of "alive"
-// elements (that will still be yielded) is the length of the range `alive`.
-// This range is decremented in length in either `next` or `next_back`. It is
-// always decremented by 1 in those methods, but only if `Some(_)` is returned.
-#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
-unsafe impl<T, const N: usize> TrustedLen for IntoIter<T, N> {}
-
-#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
-impl<T: Clone, const N: usize> Clone for IntoIter<T, N> {
-    fn clone(&self) -> Self {
-        // SAFETY: each point of unsafety is documented inside the unsafe block
-        unsafe {
-            // This creates a new uninitialized array. Note that the `assume_init`
-            // refers to the array, not the individual elements. And it is Ok if
-            // the array is in an uninitialized state as all elements may be
-            // uninitialized (all bit patterns are valid). Compare the
-            // `MaybeUninit` docs for more information.
-            let mut new_data: [MaybeUninit<T>; N] = MaybeUninit::uninit().assume_init();
-
-            // Clone all alive elements.
-            for idx in self.alive.clone() {
-                // The element at `idx` in the old array is alive, so we can
-                // safely call `get_ref()`. We then clone it, and write the
-                // clone into the new array.
-                let clone = self.data.get_unchecked(idx).get_ref().clone();
-                new_data.get_unchecked_mut(idx).write(clone);
-            }
-
-            Self { data: new_data, alive: self.alive.clone() }
-        }
-    }
-}
-
-#[stable(feature = "array_value_iter_impls", since = "1.40.0")]
-impl<T: fmt::Debug, const N: usize> fmt::Debug for IntoIter<T, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        // Only print the elements that were not yielded yet: we cannot
-        // access the yielded elements anymore.
-        f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
-    }
-}
diff --git a/src/libcore/array/mod.rs b/src/libcore/array/mod.rs
deleted file mode 100644
index c0bf3833b9c..00000000000
--- a/src/libcore/array/mod.rs
+++ /dev/null
@@ -1,366 +0,0 @@
-//! Implementations of things like `Eq` for fixed-length arrays
-//! up to a certain length. Eventually, we should be able to generalize
-//! to all lengths.
-//!
-//! *[See also the array primitive type](../../std/primitive.array.html).*
-
-#![stable(feature = "core_array", since = "1.36.0")]
-
-use crate::borrow::{Borrow, BorrowMut};
-use crate::cmp::Ordering;
-use crate::convert::{Infallible, TryFrom};
-use crate::fmt;
-use crate::hash::{self, Hash};
-use crate::marker::Unsize;
-use crate::slice::{Iter, IterMut};
-
-mod iter;
-
-#[unstable(feature = "array_value_iter", issue = "65798")]
-pub use iter::IntoIter;
-
-/// Utility trait implemented only on arrays of fixed size
-///
-/// This trait can be used to implement other traits on fixed-size arrays
-/// without causing much metadata bloat.
-///
-/// The trait is marked unsafe in order to restrict implementors to fixed-size
-/// arrays. User of this trait can assume that implementors have the exact
-/// layout in memory of a fixed size array (for example, for unsafe
-/// initialization).
-///
-/// Note that the traits [`AsRef`] and [`AsMut`] provide similar methods for types that
-/// may not be fixed-size arrays. Implementors should prefer those traits
-/// instead.
-///
-/// [`AsRef`]: ../convert/trait.AsRef.html
-/// [`AsMut`]: ../convert/trait.AsMut.html
-#[unstable(feature = "fixed_size_array", issue = "27778")]
-pub unsafe trait FixedSizeArray<T> {
-    /// Converts the array to immutable slice
-    #[unstable(feature = "fixed_size_array", issue = "27778")]
-    fn as_slice(&self) -> &[T];
-    /// Converts the array to mutable slice
-    #[unstable(feature = "fixed_size_array", issue = "27778")]
-    fn as_mut_slice(&mut self) -> &mut [T];
-}
-
-#[unstable(feature = "fixed_size_array", issue = "27778")]
-unsafe impl<T, A: Unsize<[T]>> FixedSizeArray<T> for A {
-    #[inline]
-    fn as_slice(&self) -> &[T] {
-        self
-    }
-    #[inline]
-    fn as_mut_slice(&mut self) -> &mut [T] {
-        self
-    }
-}
-
-/// The error type returned when a conversion from a slice to an array fails.
-#[stable(feature = "try_from", since = "1.34.0")]
-#[derive(Debug, Copy, Clone)]
-pub struct TryFromSliceError(());
-
-#[stable(feature = "core_array", since = "1.36.0")]
-impl fmt::Display for TryFromSliceError {
-    #[inline]
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(self.__description(), f)
-    }
-}
-
-impl TryFromSliceError {
-    #[unstable(
-        feature = "array_error_internals",
-        reason = "available through Error trait and this method should not \
-                     be exposed publicly",
-        issue = "none"
-    )]
-    #[inline]
-    #[doc(hidden)]
-    pub fn __description(&self) -> &str {
-        "could not convert slice to array"
-    }
-}
-
-#[stable(feature = "try_from_slice_error", since = "1.36.0")]
-impl From<Infallible> for TryFromSliceError {
-    fn from(x: Infallible) -> TryFromSliceError {
-        match x {}
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T, const N: usize> AsRef<[T]> for [T; N] {
-    #[inline]
-    fn as_ref(&self) -> &[T] {
-        &self[..]
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T, const N: usize> AsMut<[T]> for [T; N] {
-    #[inline]
-    fn as_mut(&mut self) -> &mut [T] {
-        &mut self[..]
-    }
-}
-
-#[stable(feature = "array_borrow", since = "1.4.0")]
-impl<T, const N: usize> Borrow<[T]> for [T; N] {
-    fn borrow(&self) -> &[T] {
-        self
-    }
-}
-
-#[stable(feature = "array_borrow", since = "1.4.0")]
-impl<T, const N: usize> BorrowMut<[T]> for [T; N] {
-    fn borrow_mut(&mut self) -> &mut [T] {
-        self
-    }
-}
-
-#[stable(feature = "try_from", since = "1.34.0")]
-impl<T, const N: usize> TryFrom<&[T]> for [T; N]
-where
-    T: Copy,
-{
-    type Error = TryFromSliceError;
-
-    fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError> {
-        <&Self>::try_from(slice).map(|r| *r)
-    }
-}
-
-#[stable(feature = "try_from", since = "1.34.0")]
-impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] {
-    type Error = TryFromSliceError;
-
-    fn try_from(slice: &[T]) -> Result<&[T; N], TryFromSliceError> {
-        if slice.len() == N {
-            let ptr = slice.as_ptr() as *const [T; N];
-            // SAFETY: ok because we just checked that the length fits
-            unsafe { Ok(&*ptr) }
-        } else {
-            Err(TryFromSliceError(()))
-        }
-    }
-}
-
-#[stable(feature = "try_from", since = "1.34.0")]
-impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] {
-    type Error = TryFromSliceError;
-
-    fn try_from(slice: &mut [T]) -> Result<&mut [T; N], TryFromSliceError> {
-        if slice.len() == N {
-            let ptr = slice.as_mut_ptr() as *mut [T; N];
-            // SAFETY: ok because we just checked that the length fits
-            unsafe { Ok(&mut *ptr) }
-        } else {
-            Err(TryFromSliceError(()))
-        }
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Hash, const N: usize> Hash for [T; N] {
-    fn hash<H: hash::Hasher>(&self, state: &mut H) {
-        Hash::hash(&self[..], state)
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: fmt::Debug, const N: usize> fmt::Debug for [T; N] {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Debug::fmt(&&self[..], f)
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T, const N: usize> IntoIterator for &'a [T; N] {
-    type Item = &'a T;
-    type IntoIter = Iter<'a, T>;
-
-    fn into_iter(self) -> Iter<'a, T> {
-        self.iter()
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N] {
-    type Item = &'a mut T;
-    type IntoIter = IterMut<'a, T>;
-
-    fn into_iter(self) -> IterMut<'a, T> {
-        self.iter_mut()
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<A, B, const N: usize> PartialEq<[B; N]> for [A; N]
-where
-    A: PartialEq<B>,
-{
-    #[inline]
-    fn eq(&self, other: &[B; N]) -> bool {
-        self[..] == other[..]
-    }
-    #[inline]
-    fn ne(&self, other: &[B; N]) -> bool {
-        self[..] != other[..]
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<A, B, const N: usize> PartialEq<[B]> for [A; N]
-where
-    A: PartialEq<B>,
-{
-    #[inline]
-    fn eq(&self, other: &[B]) -> bool {
-        self[..] == other[..]
-    }
-    #[inline]
-    fn ne(&self, other: &[B]) -> bool {
-        self[..] != other[..]
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<A, B, const N: usize> PartialEq<[A; N]> for [B]
-where
-    B: PartialEq<A>,
-{
-    #[inline]
-    fn eq(&self, other: &[A; N]) -> bool {
-        self[..] == other[..]
-    }
-    #[inline]
-    fn ne(&self, other: &[A; N]) -> bool {
-        self[..] != other[..]
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, A, B, const N: usize> PartialEq<&'b [B]> for [A; N]
-where
-    A: PartialEq<B>,
-{
-    #[inline]
-    fn eq(&self, other: &&'b [B]) -> bool {
-        self[..] == other[..]
-    }
-    #[inline]
-    fn ne(&self, other: &&'b [B]) -> bool {
-        self[..] != other[..]
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, A, B, const N: usize> PartialEq<[A; N]> for &'b [B]
-where
-    B: PartialEq<A>,
-{
-    #[inline]
-    fn eq(&self, other: &[A; N]) -> bool {
-        self[..] == other[..]
-    }
-    #[inline]
-    fn ne(&self, other: &[A; N]) -> bool {
-        self[..] != other[..]
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, A, B, const N: usize> PartialEq<&'b mut [B]> for [A; N]
-where
-    A: PartialEq<B>,
-{
-    #[inline]
-    fn eq(&self, other: &&'b mut [B]) -> bool {
-        self[..] == other[..]
-    }
-    #[inline]
-    fn ne(&self, other: &&'b mut [B]) -> bool {
-        self[..] != other[..]
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<'b, A, B, const N: usize> PartialEq<[A; N]> for &'b mut [B]
-where
-    B: PartialEq<A>,
-{
-    #[inline]
-    fn eq(&self, other: &[A; N]) -> bool {
-        self[..] == other[..]
-    }
-    #[inline]
-    fn ne(&self, other: &[A; N]) -> bool {
-        self[..] != other[..]
-    }
-}
-
-// NOTE: some less important impls are omitted to reduce code bloat
-// __impl_slice_eq2! { [A; $N], &'b [B; $N] }
-// __impl_slice_eq2! { [A; $N], &'b mut [B; $N] }
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Eq, const N: usize> Eq for [T; N] {}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: PartialOrd, const N: usize> PartialOrd for [T; N] {
-    #[inline]
-    fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering> {
-        PartialOrd::partial_cmp(&&self[..], &&other[..])
-    }
-    #[inline]
-    fn lt(&self, other: &[T; N]) -> bool {
-        PartialOrd::lt(&&self[..], &&other[..])
-    }
-    #[inline]
-    fn le(&self, other: &[T; N]) -> bool {
-        PartialOrd::le(&&self[..], &&other[..])
-    }
-    #[inline]
-    fn ge(&self, other: &[T; N]) -> bool {
-        PartialOrd::ge(&&self[..], &&other[..])
-    }
-    #[inline]
-    fn gt(&self, other: &[T; N]) -> bool {
-        PartialOrd::gt(&&self[..], &&other[..])
-    }
-}
-
-/// Implements comparison of arrays lexicographically.
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Ord, const N: usize> Ord for [T; N] {
-    #[inline]
-    fn cmp(&self, other: &[T; N]) -> Ordering {
-        Ord::cmp(&&self[..], &&other[..])
-    }
-}
-
-// The Default impls cannot be generated using the array_impls! macro because
-// they require array literals.
-
-macro_rules! array_impl_default {
-    {$n:expr, $t:ident $($ts:ident)*} => {
-        #[stable(since = "1.4.0", feature = "array_default")]
-        impl<T> Default for [T; $n] where T: Default {
-            fn default() -> [T; $n] {
-                [$t::default(), $($ts::default()),*]
-            }
-        }
-        array_impl_default!{($n - 1), $($ts)*}
-    };
-    {$n:expr,} => {
-        #[stable(since = "1.4.0", feature = "array_default")]
-        impl<T> Default for [T; $n] {
-            fn default() -> [T; $n] { [] }
-        }
-    };
-}
-
-array_impl_default! {32, T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T}