Re: [PATCH 1/4] rust: add projection infrastructure

[Gary Guo]

On 2026-02-22 00:57, Benno Lossin wrote:
> On Sat Feb 14, 2026 at 6:33 AM CET, Gary Guo wrote:
> > +#[macro_export]
> > +macro_rules! project_pointer {
> > +    (@gen $ptr:ident, ) => {};
> > +    // Field projection. `$field` needs to be `tt` to support tuple 
> > index like `.0`.
> > +    (@gen $ptr:ident, .$field:tt $($rest:tt)*) => {
> > +        // SAFETY: the provided closure always return in bounds 
> > pointer.
> > +        let $ptr = unsafe {
> > +            $crate::projection::ProjectField::proj($ptr, 
> > #[inline(always)] |ptr| {
>
> By the way, how does this avoid `#![feature(stmt_expr_attributes)]`?

I don't know how, but attributes on closures passed direclty to 
functions has been stable
for basically ~forever. A quick check says that this is available since 
Rust 1.11.

Best,
Gary

> Cheers,
> Benno
>
> > +                // SAFETY: `$field` is in bounds, and no implicit 
> > `Deref` is possible (if the
> > +                // type implements `Deref`, Rust cannot infer the 
> > generic parameter `DEREF`).
> > +                &raw mut (*ptr).$field
> > +            })
> > +        };
> > +        $crate::project_pointer!(@gen $ptr, $($rest)*)
> > +    };