Miri failure on rustc 1.73.0-nightly (31395ec38 2023-07-24)

[lopopolo]

https://github.com/artichoke/intaglio/actions/runs/5663120563/job/15344308090

error: Undefined Behavior: trying to retag from <99387> for SharedReadOnly permission at alloc31495[0x0], but that tag does not exist in the borrow stack for this location
   --> /home/runner/work/intaglio/intaglio/src/bytes.rs:713:45
    |
713 |         debug_assert_eq!(self.get(id), Some(slice));
    |                                             ^^^^^
    |                                             |
    |                                             trying to retag from <99387> for SharedReadOnly permission at alloc31495[0x0], but that tag does not exist in the borrow stack for this location
    |                                             this error occurs as part of retag at alloc31495[0x0..0x64]
    |
    = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
    = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
help: <99387> was created by a SharedReadOnly retag at offsets [0x0..0x64]
   --> /home/runner/work/intaglio/intaglio/src/bytes.rs:708:30
    |
708 |         let slice = unsafe { name.as_static_slice() };
    |                              ^^^^^^^^^^^^^^^^^^^^^^
help: <99387> was later invalidated at offsets [0x0..0x64] by a Unique retag (of a reference/box inside this compound value)
   --> /home/runner/work/intaglio/intaglio/src/bytes.rs:711:23
    |
711 |         self.vec.push(name);
    |                       ^^^^
    = note: BACKTRACE (of the first span):
    = note: inside `intaglio::bytes::SymbolTable::intern::<std::vec::Vec<u8>>` at /home/runner/work/intaglio/intaglio/src/bytes.rs:713:45: 713:50
note: inside `bytes::dealloc_owned_data`
   --> tests/leak_drop/bytes.rs:9:22
    |
9   |         let sym_id = table.intern(symbol.clone()).unwrap();
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: inside closure
   --> tests/leak_drop/bytes.rs:4:25
    |
3   | #[test]
    | ------- in this procedural macro expansion
4   | fn dealloc_owned_data() {
    |                         ^
    = note: this error originates in the attribute macro `test` (in Nightly builds, run with -Z macro-backtrace for more info)

note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

error: aborting due to previous error

error: test failed, to rerun pass `--test leak_drop`

[lopopolo]

Implicated code:

intaglio/src/bytes.rs

Lines 687 to 717 in 70ccd8b

	pub fn intern<T>(&mut self, contents: T) -> Result<Symbol, SymbolOverflowError>
	where
	T: Into<Cow<'static, [u8]>>,
	{
	let contents = contents.into();
	if let Some(&id) = self.map.get(&*contents) {
	return Ok(id);
	}
	let name = Interned::from(contents);
	let id = self.map.len().try_into()?;
	// SAFETY: This expression creates a reference with a `'static` lifetime
	// from an owned and interned buffer, which is permissible because:
	//
	// - `Interned` is an internal implementation detail of `SymbolTable`.
	// - `SymbolTable` never gives out `'static` references to underlying
	// byte string byte contents.
	// - All slice references given out by the `SymbolTable` have the same
	// lifetime as the `SymbolTable`.
	// - The `map` field of `SymbolTable`, which contains the `'static`
	// references, is dropped before the owned buffers stored in this
	// `Interned`.
	let slice = unsafe { name.as_static_slice() };
	self.map.insert(slice, id);
	self.vec.push(name);
	debug_assert_eq!(self.get(id), Some(slice));
	debug_assert_eq!(self.intern(slice), Ok(id));
	Ok(id)
	}