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).

1 files changed, 0 insertions, 289 deletions

diff --git a/src/libcore/ops/function.rs b/src/libcore/ops/function.rs
deleted file mode 100644
index 3e5cad2b185..00000000000
--- a/src/libcore/ops/function.rs
+++ /dev/null
@@ -1,289 +0,0 @@
-/// The version of the call operator that takes an immutable receiver.
-///
-/// Instances of `Fn` can be called repeatedly without mutating state.
-///
-/// *This trait (`Fn`) is not to be confused with [function pointers]
-/// (`fn`).*
-///
-/// `Fn` is implemented automatically by closures which only take immutable
-/// references to captured variables or don't capture anything at all, as well
-/// as (safe) [function pointers] (with some caveats, see their documentation
-/// for more details). Additionally, for any type `F` that implements `Fn`, `&F`
-/// implements `Fn`, too.
-///
-/// Since both [`FnMut`] and [`FnOnce`] are supertraits of `Fn`, any
-/// instance of `Fn` can be used as a parameter where a [`FnMut`] or [`FnOnce`]
-/// is expected.
-///
-/// Use `Fn` as a bound when you want to accept a parameter of function-like
-/// type and need to call it repeatedly and without mutating state (e.g., when
-/// calling it concurrently). If you do not need such strict requirements, use
-/// [`FnMut`] or [`FnOnce`] as bounds.
-///
-/// See the [chapter on closures in *The Rust Programming Language*][book] for
-/// some more information on this topic.
-///
-/// Also of note is the special syntax for `Fn` traits (e.g.
-/// `Fn(usize, bool) -> usize`). Those interested in the technical details of
-/// this can refer to [the relevant section in the *Rustonomicon*][nomicon].
-///
-/// [book]: ../../book/ch13-01-closures.html
-/// [`FnMut`]: trait.FnMut.html
-/// [`FnOnce`]: trait.FnOnce.html
-/// [function pointers]: ../../std/primitive.fn.html
-/// [nomicon]: ../../nomicon/hrtb.html
-///
-/// # Examples
-///
-/// ## Calling a closure
-///
-/// ```
-/// let square = |x| x * x;
-/// assert_eq!(square(5), 25);
-/// ```
-///
-/// ## Using a `Fn` parameter
-///
-/// ```
-/// fn call_with_one<F>(func: F) -> usize
-///     where F: Fn(usize) -> usize {
-///     func(1)
-/// }
-///
-/// let double = |x| x * 2;
-/// assert_eq!(call_with_one(double), 2);
-/// ```
-#[lang = "fn"]
-#[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_paren_sugar]
-#[rustc_on_unimplemented(
-    on(
-        Args = "()",
-        note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
-    ),
-    message = "expected a `{Fn}<{Args}>` closure, found `{Self}`",
-    label = "expected an `Fn<{Args}>` closure, found `{Self}`"
-)]
-#[fundamental] // so that regex can rely that `&str: !FnMut`
-#[must_use = "closures are lazy and do nothing unless called"]
-pub trait Fn<Args>: FnMut<Args> {
-    /// Performs the call operation.
-    #[unstable(feature = "fn_traits", issue = "29625")]
-    extern "rust-call" fn call(&self, args: Args) -> Self::Output;
-}
-
-/// The version of the call operator that takes a mutable receiver.
-///
-/// Instances of `FnMut` can be called repeatedly and may mutate state.
-///
-/// `FnMut` is implemented automatically by closures which take mutable
-/// references to captured variables, as well as all types that implement
-/// [`Fn`], e.g., (safe) [function pointers] (since `FnMut` is a supertrait of
-/// [`Fn`]). Additionally, for any type `F` that implements `FnMut`, `&mut F`
-/// implements `FnMut`, too.
-///
-/// Since [`FnOnce`] is a supertrait of `FnMut`, any instance of `FnMut` can be
-/// used where a [`FnOnce`] is expected, and since [`Fn`] is a subtrait of
-/// `FnMut`, any instance of [`Fn`] can be used where `FnMut` is expected.
-///
-/// Use `FnMut` as a bound when you want to accept a parameter of function-like
-/// type and need to call it repeatedly, while allowing it to mutate state.
-/// If you don't want the parameter to mutate state, use [`Fn`] as a
-/// bound; if you don't need to call it repeatedly, use [`FnOnce`].
-///
-/// See the [chapter on closures in *The Rust Programming Language*][book] for
-/// some more information on this topic.
-///
-/// Also of note is the special syntax for `Fn` traits (e.g.
-/// `Fn(usize, bool) -> usize`). Those interested in the technical details of
-/// this can refer to [the relevant section in the *Rustonomicon*][nomicon].
-///
-/// [book]: ../../book/ch13-01-closures.html
-/// [`Fn`]: trait.Fn.html
-/// [`FnOnce`]: trait.FnOnce.html
-/// [function pointers]: ../../std/primitive.fn.html
-/// [nomicon]: ../../nomicon/hrtb.html
-///
-/// # Examples
-///
-/// ## Calling a mutably capturing closure
-///
-/// ```
-/// let mut x = 5;
-/// {
-///     let mut square_x = || x *= x;
-///     square_x();
-/// }
-/// assert_eq!(x, 25);
-/// ```
-///
-/// ## Using a `FnMut` parameter
-///
-/// ```
-/// fn do_twice<F>(mut func: F)
-///     where F: FnMut()
-/// {
-///     func();
-///     func();
-/// }
-///
-/// let mut x: usize = 1;
-/// {
-///     let add_two_to_x = || x += 2;
-///     do_twice(add_two_to_x);
-/// }
-///
-/// assert_eq!(x, 5);
-/// ```
-#[lang = "fn_mut"]
-#[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_paren_sugar]
-#[rustc_on_unimplemented(
-    on(
-        Args = "()",
-        note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
-    ),
-    message = "expected a `{FnMut}<{Args}>` closure, found `{Self}`",
-    label = "expected an `FnMut<{Args}>` closure, found `{Self}`"
-)]
-#[fundamental] // so that regex can rely that `&str: !FnMut`
-#[must_use = "closures are lazy and do nothing unless called"]
-pub trait FnMut<Args>: FnOnce<Args> {
-    /// Performs the call operation.
-    #[unstable(feature = "fn_traits", issue = "29625")]
-    extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output;
-}
-
-/// The version of the call operator that takes a by-value receiver.
-///
-/// Instances of `FnOnce` can be called, but might not be callable multiple
-/// times. Because of this, if the only thing known about a type is that it
-/// implements `FnOnce`, it can only be called once.
-///
-/// `FnOnce` is implemented automatically by closures that might consume captured
-/// variables, as well as all types that implement [`FnMut`], e.g., (safe)
-/// [function pointers] (since `FnOnce` is a supertrait of [`FnMut`]).
-///
-/// Since both [`Fn`] and [`FnMut`] are subtraits of `FnOnce`, any instance of
-/// [`Fn`] or [`FnMut`] can be used where a `FnOnce` is expected.
-///
-/// Use `FnOnce` as a bound when you want to accept a parameter of function-like
-/// type and only need to call it once. If you need to call the parameter
-/// repeatedly, use [`FnMut`] as a bound; if you also need it to not mutate
-/// state, use [`Fn`].
-///
-/// See the [chapter on closures in *The Rust Programming Language*][book] for
-/// some more information on this topic.
-///
-/// Also of note is the special syntax for `Fn` traits (e.g.
-/// `Fn(usize, bool) -> usize`). Those interested in the technical details of
-/// this can refer to [the relevant section in the *Rustonomicon*][nomicon].
-///
-/// [book]: ../../book/ch13-01-closures.html
-/// [`Fn`]: trait.Fn.html
-/// [`FnMut`]: trait.FnMut.html
-/// [function pointers]: ../../std/primitive.fn.html
-/// [nomicon]: ../../nomicon/hrtb.html
-///
-/// # Examples
-///
-/// ## Using a `FnOnce` parameter
-///
-/// ```
-/// fn consume_with_relish<F>(func: F)
-///     where F: FnOnce() -> String
-/// {
-///     // `func` consumes its captured variables, so it cannot be run more
-///     // than once.
-///     println!("Consumed: {}", func());
-///
-///     println!("Delicious!");
-///
-///     // Attempting to invoke `func()` again will throw a `use of moved
-///     // value` error for `func`.
-/// }
-///
-/// let x = String::from("x");
-/// let consume_and_return_x = move || x;
-/// consume_with_relish(consume_and_return_x);
-///
-/// // `consume_and_return_x` can no longer be invoked at this point
-/// ```
-#[lang = "fn_once"]
-#[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_paren_sugar]
-#[rustc_on_unimplemented(
-    on(
-        Args = "()",
-        note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
-    ),
-    message = "expected a `{FnOnce}<{Args}>` closure, found `{Self}`",
-    label = "expected an `FnOnce<{Args}>` closure, found `{Self}`"
-)]
-#[fundamental] // so that regex can rely that `&str: !FnMut`
-#[must_use = "closures are lazy and do nothing unless called"]
-pub trait FnOnce<Args> {
-    /// The returned type after the call operator is used.
-    #[lang = "fn_once_output"]
-    #[stable(feature = "fn_once_output", since = "1.12.0")]
-    type Output;
-
-    /// Performs the call operation.
-    #[unstable(feature = "fn_traits", issue = "29625")]
-    extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
-}
-
-mod impls {
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A, F: ?Sized> Fn<A> for &F
-    where
-        F: Fn<A>,
-    {
-        extern "rust-call" fn call(&self, args: A) -> F::Output {
-            (**self).call(args)
-        }
-    }
-
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A, F: ?Sized> FnMut<A> for &F
-    where
-        F: Fn<A>,
-    {
-        extern "rust-call" fn call_mut(&mut self, args: A) -> F::Output {
-            (**self).call(args)
-        }
-    }
-
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A, F: ?Sized> FnOnce<A> for &F
-    where
-        F: Fn<A>,
-    {
-        type Output = F::Output;
-
-        extern "rust-call" fn call_once(self, args: A) -> F::Output {
-            (*self).call(args)
-        }
-    }
-
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A, F: ?Sized> FnMut<A> for &mut F
-    where
-        F: FnMut<A>,
-    {
-        extern "rust-call" fn call_mut(&mut self, args: A) -> F::Output {
-            (*self).call_mut(args)
-        }
-    }
-
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl<A, F: ?Sized> FnOnce<A> for &mut F
-    where
-        F: FnMut<A>,
-    {
-        type Output = F::Output;
-        extern "rust-call" fn call_once(self, args: A) -> F::Output {
-            (*self).call_mut(args)
-        }
-    }
-}