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    //! # The Rust core allocation and collections library
    //!
    //! This library provides smart pointers and collections for managing
    //! heap-allocated values.
    //!
    //! This library, like libcore, normally doesn’t need to be used directly
    //! since its contents are re-exported in the [`std` crate](../std/index.html).
    //! Crates that use the `#![no_std]` attribute however will typically
    //! not depend on `std`, so they’d use this crate instead.
    //!
    //! ## Boxed values
    //!
    //! The [`Box`] type is a smart pointer type. There can only be one owner of a
    //! [`Box`], and the owner can decide to mutate the contents, which live on the
    //! heap.
    //!
    //! This type can be sent among threads efficiently as the size of a `Box` value
    //! is the same as that of a pointer. Tree-like data structures are often built
    //! with boxes because each node often has only one owner, the parent.
    //!
    //! ## Reference counted pointers
    //!
    //! The [`Rc`] type is a non-threadsafe reference-counted pointer type intended
    //! for sharing memory within a thread. An [`Rc`] pointer wraps a type, `T`, and
    //! only allows access to `&T`, a shared reference.
    //!
    //! This type is useful when inherited mutability (such as using [`Box`]) is too
    //! constraining for an application, and is often paired with the [`Cell`] or
    //! [`RefCell`] types in order to allow mutation.
    //!
    //! ## Atomically reference counted pointers
    //!
    //! The [`Arc`] type is the threadsafe equivalent of the [`Rc`] type. It
    //! provides all the same functionality of [`Rc`], except it requires that the
    //! contained type `T` is shareable. Additionally, [`Arc<T>`][`Arc`] is itself
    //! sendable while [`Rc<T>`][`Rc`] is not.
    //!
    //! This type allows for shared access to the contained data, and is often
    //! paired with synchronization primitives such as mutexes to allow mutation of
    //! shared resources.
    //!
    //! ## Collections
    //!
    //! Implementations of the most common general purpose data structures are
    //! defined in this library. They are re-exported through the
    //! [standard collections library](../std/collections/index.html).
    //!
    //! ## Heap interfaces
    //!
    //! The [`alloc`](alloc/index.html) module defines the low-level interface to the
    //! default global allocator. It is not compatible with the libc allocator API.
    //!
    //! [`Arc`]: sync/index.html
    //! [`Box`]: boxed/index.html
    //! [`Cell`]: ../core/cell/index.html
    //! [`Rc`]: rc/index.html
    //! [`RefCell`]: ../core/cell/index.html

    #![allow(unused_attributes)]
    #![stable(feature = "alloc", since = "1.36.0")]
    #![doc(
        html_root_url = "https://doc.rust-lang.org/nightly/",
        html_playground_url = "https://play.rust-lang.org/",
        issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
        test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
    )]
    #![no_std]
    #![needs_allocator]
    #![warn(deprecated_in_future)]
    #![warn(missing_docs)]
    #![warn(missing_debug_implementations)]
    #![deny(intra_doc_link_resolution_failure)] // rustdoc is run without -D warnings
    #![allow(explicit_outlives_requirements)]
    #![allow(incomplete_features)]
    #![cfg_attr(not(test), feature(generator_trait))]
    #![cfg_attr(test, feature(test))]
    #![feature(allocator_api)]
    #![feature(allow_internal_unstable)]
    #![feature(arbitrary_self_types)]
    #![feature(box_into_raw_non_null)]
    #![feature(box_patterns)]
    #![feature(box_syntax)]
    #![feature(cfg_target_has_atomic)]
    #![feature(coerce_unsized)]
    #![feature(const_generic_impls_guard)]
    #![feature(const_generics)]
    #![feature(const_in_array_repeat_expressions)]
    #![feature(const_if_match)]
    #![feature(cow_is_borrowed)]
    #![feature(dispatch_from_dyn)]
    #![feature(core_intrinsics)]
    #![feature(container_error_extra)]
    #![feature(dropck_eyepatch)]
    #![feature(exact_size_is_empty)]
    #![feature(fmt_internals)]
    #![feature(fn_traits)]
    #![feature(fundamental)]
    #![feature(internal_uninit_const)]
    #![feature(lang_items)]
    #![feature(libc)]
    #![feature(nll)]
    #![feature(optin_builtin_traits)]
    #![feature(pattern)]
    #![feature(ptr_internals)]
    #![feature(ptr_offset_from)]
    #![feature(rustc_attrs)]
    #![feature(receiver_trait)]
    #![feature(specialization)]
    #![feature(staged_api)]
    #![feature(std_internals)]
    #![feature(str_internals)]
    #![feature(trusted_len)]
    #![feature(try_reserve)]
    #![feature(unboxed_closures)]
    #![feature(unicode_internals)]
    #![feature(unsize)]
    #![feature(unsized_locals)]
    #![feature(allocator_internals)]
    #![feature(slice_partition_dedup)]
    #![feature(maybe_uninit_extra, maybe_uninit_slice)]
    #![feature(alloc_layout_extra)]
    #![feature(try_trait)]
    #![feature(associated_type_bounds)]

    // Allow testing this library

    #[cfg(test)]
    #[macro_use]
    extern crate std;
    #[cfg(test)]
    extern crate test;

    // Module with internal macros used by other modules (needs to be included before other modules).
    #[macro_use]
    mod macros;

    // Heaps provided for low-level allocation strategies

    pub mod alloc;

    // Primitive types using the heaps above

    // Need to conditionally define the mod from `boxed.rs` to avoid
    // duplicating the lang-items when building in test cfg; but also need
    // to allow code to have `use boxed::Box;` declarations.
    #[cfg(not(test))]
    pub mod boxed;
    #[cfg(test)]
    mod boxed {
        pub use std::boxed::Box;
    }
    pub mod borrow;
    pub mod collections;
    pub mod fmt;
    pub mod prelude;
    pub mod raw_vec;
    pub mod rc;
    pub mod slice;
    pub mod str;
    pub mod string;
    #[cfg(target_has_atomic = "ptr")]
    pub mod sync;
    #[cfg(test)]
    mod tests;
    pub mod vec;

    #[cfg(not(test))]
    mod std {
        pub use core::ops; // RangeFull
    }

    #[doc(hidden)]
    #[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
    pub mod __export {
        pub use core::format_args;
    }