linux-kernel - Re: [PATCH] rust: error: allow specifying error type on `Result`

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Date:   Mon, 8 May 2023 12:39:53 +0100
From:   Gary Guo <gary@...yguo.net>
To:     Alice Ryhl <aliceryhl@...gle.com>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Björn Roy Baron" <bjorn3_gh@...tonmail.com>,
        Benno Lossin <benno.lossin@...ton.me>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev
Subject: Re: [PATCH] rust: error: allow specifying error type on `Result`

On Tue,  2 May 2023 12:40:15 +0000
Alice Ryhl <aliceryhl@...gle.com> wrote:

> Currently, if the `kernel::error::Result` type is in scope (which is
> often is, since it's in the kernel's prelude), you cannot write
> `Result<T, SomeOtherErrorType>` when you want to use a different error
> type than `kernel::error::Error`.
> 
> To solve this we change the error type from being hard-coded to just
> being a default generic parameter. This still lets you write `Result<T>`
> when you just want to use the `Error` error type, but also lets you
> write `Result<T, SomeOtherErrorType>` when necessary.
> 
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>

Reviewed-by: Gary Guo <gary@...yguo.net>

> ---
>  rust/kernel/error.rs | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
> index 5f4114b30b94..01dd4d2f63d2 100644
> --- a/rust/kernel/error.rs
> +++ b/rust/kernel/error.rs
> @@ -177,7 +177,7 @@ impl From<core::convert::Infallible> for Error {
>  /// Note that even if a function does not return anything when it succeeds,
>  /// it should still be modeled as returning a `Result` rather than
>  /// just an [`Error`].
> -pub type Result<T = ()> = core::result::Result<T, Error>;
> +pub type Result<T = (), E = Error> = core::result::Result<T, E>;
>  
>  /// Converts an integer as returned by a C kernel function to an error if it's negative, and
>  /// `Ok(())` otherwise.
> 
> base-commit: ea76e08f4d901a450619831a255e9e0a4c0ed162