Re: [PATCH v3 03/12] rust: xarray: add `contains_index` method

[Alice Ryhl]

On Thu, Feb 12, 2026 at 12:49:09PM -0500, Liam R. Howlett wrote:
> * Andreas Hindborg <a.hindborg@xxxxxxxxxx> [260212 07:40]:
> > "Alice Ryhl" <aliceryhl@xxxxxxxxxx> writes:
> > 
> > > On Thu, Feb 12, 2026 at 11:52 AM Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:
> > >>
> > >> Andreas Hindborg <a.hindborg@xxxxxxxxxx> writes:
> > >>
> > >> > As far as I understand, this is a borrow checker limitation. It is easy
> > >> > for us to look at this code and decide that the borrow on line 51 will
> > >> > never alias with the borrow on line 49.
> > >>
> > >> I did a bit of googling, and this seems to be a well known issue with
> > >> the current implementation of lifetime analysis in the rust compiler.
> > >> Apparently this kind of code used to be OK [1] but the Rust devs decided
> > >> to remove the code that allowed this, because it was causing excessive
> > >> compilation times [2]. The upside is that this is solved by the new
> > >> lifetime analysis implementation called "Polonius" and it is the
> > >> intention to replace the existing implementation with Polonius at some
> > >> point [3].
> > >
> > > I believe the standard fix for this issue is to provide an entry api
> > > similar to HashMap::entry(). See the rbtree for an example, as it
> > > already provides such API.
> 
> Alice, can you provide a link to the rbtree code please?

Please see rust/kernel/rbtree.rs in the kernel tree.

Alice