linux-kernel - Re: [PATCH v2 05/12] rust: init: make initializer values inaccessible after initializing

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Message-ID: <20230720131935.3542850-1-aliceryhl@google.com>
Date:   Thu, 20 Jul 2023 13:19:35 +0000
From:   Alice Ryhl <aliceryhl@...gle.com>
To:     benno.lossin@...ton.me
Cc:     alex.gaynor@...il.com, aliceryhl@...gle.com,
        bjorn3_gh@...tonmail.com, boqun.feng@...il.com, gary@...yguo.net,
        linux-kernel@...r.kernel.org, nmi@...aspace.dk, ojeda@...nel.org,
        rust-for-linux@...r.kernel.org, wedsonaf@...il.com
Subject: Re: [PATCH v2 05/12] rust: init: make initializer values inaccessible
 after initializing

> Previously the init macros would create a local variable with the name
> and hygiene of the field that is being initialized to store the value of
> the field. This would override any user defined variables. For example:
> ```
> struct Foo {
>     a: usize,
>     b: usize,
> }
> let a = 10;
> let foo = init!(Foo{
>     a: a + 1, // This creates a local variable named `a`.
>     b: a, // This refers to that variable!
> });
> let foo = Box::init!(foo)?;
> assert_eq!(foo.a, 11);
> assert_eq!(foo.b, 11);
> ```
> 
> This patch changes this behavior, so the above code would panic at the
> last assertion, since `b` would have value 10.
> 
> Signed-off-by: Benno Lossin <benno.lossin@...ton.me>
 
Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>