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Date:   Tue,  2 May 2023 12:40:15 +0000
Mime-Version: 1.0
Message-ID: <20230502124015.356001-1-aliceryhl@google.com>
Subject: [PATCH] rust: error: allow specifying error type on `Result`
From:   Alice Ryhl <aliceryhl@google.com>
To:     Miguel Ojeda <ojeda@kernel.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Alex Gaynor <alex.gaynor@gmail.com>
Cc:     Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        "=?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?=" <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev, Alice Ryhl <aliceryhl@google.com>
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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@google.com>
---
 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
-- 
2.40.1.495.gc816e09b53d-goog