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From:   ojeda@kernel.org
To:     Miguel Ojeda <ojeda@kernel.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= <bjorn3_gh@protonmail.com>
Cc:     rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev, Wei Liu <wei.liu@kernel.org>
Subject: [PATCH v2 27/28] rust: types: add `Either` type
Date:   Fri,  2 Dec 2022 17:14:58 +0100
Message-Id: <20221202161502.385525-28-ojeda@kernel.org>
In-Reply-To: <20221202161502.385525-1-ojeda@kernel.org>
References: <20221202161502.385525-1-ojeda@kernel.org>
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From: Wedson Almeida Filho <wedsonaf@gmail.com>

Introduce the new `types` module of the `kernel` crate with
`Either` as its first type.

`Either<L, R>` is a sum type that always holds either a value
of type `L` (`Left` variant) or `R` (`Right` variant).

For instance:

    struct Executor {
        queue: Either<BoxedQueue, &'static Queue>,
    }

Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
[Reworded, adapted for upstream and applied latest changes]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/kernel/lib.rs   |  1 +
 rust/kernel/types.rs | 12 ++++++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 rust/kernel/types.rs

diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index a3abc110ff97..53040fa9e897 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -31,6 +31,7 @@ mod static_assert;
 #[doc(hidden)]
 pub mod std_vendor;
 pub mod str;
+pub mod types;
 
 #[doc(hidden)]
 pub use bindings;
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
new file mode 100644
index 000000000000..3b0c44769708
--- /dev/null
+++ b/rust/kernel/types.rs
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Kernel types.
+
+/// A sum type that always holds either a value of type `L` or `R`.
+pub enum Either<L, R> {
+    /// Constructs an instance of [`Either`] containing a value of type `L`.
+    Left(L),
+
+    /// Constructs an instance of [`Either`] containing a value of type `R`.
+    Right(R),
+}
-- 
2.38.1