//@ check-pass
#![feature(generic_const_exprs)]
#![allow(incomplete_features)]
use std::marker::PhantomData;
pub struct Equal<const T: usize, const R: usize>();
pub trait True {}
impl<const T: usize> True for Equal<T, T> {}
// replacement for generativity
pub struct Id<'id>(PhantomData<fn(&'id ()) -> &'id ()>);
pub struct Guard<'id>(Id<'id>);
fn make_guard<'id>(i: &'id Id<'id>) -> Guard<'id> {
Guard(Id(PhantomData))
}
impl<'id> Into<Id<'id>> for Guard<'id> {
fn into(self) -> Id<'id> {
self.0
}
}
pub struct Arena<'life> {
bytes: *mut [u8],
//bitmap: RefCell<RoaringBitmap>,
_token: PhantomData<Id<'life>>,
}
#[repr(transparent)]
pub struct Item<'life, T> {
data: T,
_phantom: PhantomData<Id<'life>>,
}
#[repr(transparent)]
pub struct Token<'life, 'borrow, 'compact, 'reborrow, T>
where
'life: 'reborrow,
T: Tokenize<'life, 'borrow, 'compact, 'reborrow>,
{
//ptr: *mut <T as Tokenize>::Tokenized,
ptr: core::ptr::NonNull<T::Tokenized>,
_phantom: PhantomData<Id<'life>>,
_compact: PhantomData<&'borrow Guard<'compact>>,
_result: PhantomData<&'reborrow T::Untokenized>,
}
impl<'life> Arena<'life> {
pub fn tokenize<'before, 'compact, 'borrow, 'reborrow, T, U>(
&self,
guard: &'borrow Guard<'compact>,
item: Item<'life, &'before mut T>,
) -> Token<'life, 'borrow, 'compact, 'reborrow, U>
where
T: Tokenize<'life, 'borrow, 'compact, 'reborrow, Untokenized = U>,
T::Untokenized: Tokenize<'life, 'borrow, 'compact, 'reborrow>,
Equal<{ core::mem::size_of::<T>() }, { core::mem::size_of::<U>() }>: True,
'compact: 'borrow,
'life: 'reborrow,
'life: 'compact,
'life: 'borrow,
// 'borrow: 'before ??
{
let dst = item.data as *mut T as *mut T::Tokenized;
Token {
ptr: core::ptr::NonNull::new(dst as *mut _).unwrap(),
_phantom: PhantomData,
_compact: PhantomData,
_result: PhantomData,
}
}
}
pub trait Tokenize<'life, 'borrow, 'compact, 'reborrow>
where
'compact: 'borrow,
'life: 'reborrow,
'life: 'borrow,
'life: 'compact,
{
type Tokenized;
type Untokenized;
const TO: fn(&Arena<'life>, &'borrow Guard<'compact>, Self) -> Self::Tokenized;
const FROM: fn(&'reborrow Arena<'life>, Self::Tokenized) -> Self::Untokenized;
}
macro_rules! tokenize {
($to:expr, $from:expr) => {
const TO: fn(&Arena<'life>, &'borrow Guard<'compact>, Self) -> Self::Tokenized = $to;
const FROM: fn(&'reborrow Arena<'life>, Self::Tokenized) -> Self::Untokenized = $from;
};
}
struct Foo<'life, 'borrow>(Option<Item<'life, &'borrow mut Bar>>);
struct TokenFoo<'life, 'borrow, 'compact, 'reborrow>(
Option<Token<'life, 'borrow, 'compact, 'reborrow, Bar>>,
);
struct Bar(u8);
impl<'life, 'before, 'borrow, 'compact, 'reborrow> Tokenize<'life, 'borrow, 'compact, 'reborrow>
for Foo<'life, 'before>
where
'compact: 'borrow,
'life: 'reborrow,
'life: 'borrow,
'life: 'compact,
{
type Tokenized = TokenFoo<'life, 'borrow, 'compact, 'reborrow>;
type Untokenized = Foo<'life, 'reborrow>;
tokenize!(foo_to, foo_from);
}
impl<'life, 'borrow, 'compact, 'reborrow> Tokenize<'life, 'borrow, 'compact, 'reborrow> for Bar
where
'compact: 'borrow,
'life: 'reborrow,
'life: 'borrow,
'life: 'compact,
{
type Tokenized = Bar;
type Untokenized = Bar;
tokenize!(bar_to, bar_from);
}
fn bar_to<'life, 'borrow, 'compact>(
arena: &Arena<'life>,
guard: &'borrow Guard<'compact>,
s: Bar,
) -> Bar {
s
}
fn bar_from<'life, 'reborrow>(arena: &'reborrow Arena<'life>, s: Bar) -> Bar {
s
}
fn foo_to<'life, 'borrow, 'compact, 'reborrow, 'before>(
arena: &'before Arena<'life>,
guard: &'borrow Guard<'compact>,
s: Foo<'life, 'before>,
) -> TokenFoo<'life, 'borrow, 'compact, 'reborrow> {
let Foo(bar) = s;
TokenFoo(bar.map(|bar| arena.tokenize(guard, bar)))
}
fn foo_from<'life, 'borrow, 'compact, 'reborrow>(
arena: &'reborrow Arena<'life>,
s: TokenFoo<'life, 'borrow, 'compact, 'reborrow>,
) -> Foo<'life, 'reborrow> {
Foo(s.0.map(|bar| panic!()))
}
fn main() {}rustdoc 1.94.0-nightly (0f0d850e9 2025-12-19)
binary: rustdoc
commit-hash: 0f0d850e9146f53b16fb1c6a56ed2f821962ff94
commit-date: 2025-12-19
host: x86_64-unknown-linux-gnu
release: 1.94.0-nightly
LLVM version: 21.1.8
Code
Meta
rustc --version --verbose:Error output
rustdoc -Zunstable-options --generate-macro-expansionBacktrace