Re: [PATCH] rust: pin-init: add references to previously initialized fields

[Boqun Feng <boqun.feng@gmail.com>]

On Fri, Sep 05, 2025 at 07:18:25PM +0200, Benno Lossin wrote:
[...]
> index 606946ff4d7f..1ac0b06fa3b3 100644
> --- a/samples/rust/rust_driver_pci.rs
> +++ b/samples/rust/rust_driver_pci.rs
> @@ -78,8 +78,8 @@ fn probe(pdev: &pci::Device<Core>, info: &Self::IdInfo) -> Result<Pin<KBox<Self>
>  
>          let drvdata = KBox::pin_init(
>              try_pin_init!(Self {
> -                pdev: pdev.into(),
>                  bar <- pdev.iomap_region_sized::<{ Regs::END }>(0, c_str!("rust_driver_pci")),
> +                pdev: pdev.into(),

Ok, this example is good enough for me to express the concern here: the
variable shadowing behavior seems not straightforward (maybe because in
normal Rust initalization expression, no binding is created for
previous variables, neither do we have a `let` here).

Would the future inplace initialization have the similar behavior? I
asked because a natural resolution is adding a special syntax like:

    let a = ..;

    try_pin_init!(Self {
        b: a,
	let a = a.into(); // create the new binding here.
	c: a, // <- use the previous initalized `a`.
    }

(Since I lost tracking of the discussion a bit, maybe there is a
previous discussion I've missed here?)

Regards,
Boqun

>                  index: *info,
>              }),
>              GFP_KERNEL,