Tracking Issue for const_default_impls

[fee1-dead]

Feature gate: #![feature(const_default_impls)]

This is a tracking issue for const Default impls in the standard library.

Public API

// core::array
impl<T> const Default for [T; 0];

// core::default
impl const Default for ();
impl const Default for bool;
impl const Default for char;
impl const Default for usize;
impl const Default for u8;
impl const Default for u16;
impl const Default for u32;
impl const Default for u64;
impl const Default for u128;
impl const Default for isize;
impl const Default for i8;
impl const Default for i16;
impl const Default for i32;
impl const Default for i64;
impl const Default for i128;
impl const Default for f32;
impl const Default for f64;

// core::hash
impl<H> const Default for BuildHasherDefault<H>;

// core::iter
impl<T> const Default for Empty<T>;

// core::marker
impl<T: ?Sized> const Default for PhantomData<T>;

// core::option
impl<T> const Default for Option<T>;

// core::slice
impl<T> const Default for &[T];
impl<T> const Default for &mut [T];

// core::str
impl const Default for &str;

// core::sync::atomic
impl const Default for AtomicBool;
impl<T> const Default for AtomicPtr<T>;

// alloc::boxed
impl<T> const Default for Box<[T]>;
impl const Default for Box<str>;

// alloc::string
impl const Default for String;

// alloc::vec
impl<T> const Default for Vec<T>;

// std::lazy
impl<T> const Default for SyncOnceCell<T>;

Steps / History

• Implementation: constified implementations of Default #86808, impl const Default for Box<[T]> and Box<str> #95947
• Final comment period (FCP)
• Stabilization PR

Unresolved Questions

• None yet.

[DesmondWillowbrook]

What's the status of this issue?

[Liamolucko]

It's dependent on #67792.

[C0D3-M4513R]

I stumbled across this pr, as I was trying to implement my own const Default implementations and ran into various errors:
https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=36cb0ae9a38d3d57000dce3173d38df2

What am I doing wrong here?

[fee1-dead]

See #110395.