[PATCH v3] rust: Implement Display for Box

[Guangbo Cui <2407018371@qq.com>]

Currently `impl Display` is missing for `Box<T, A>`, as a result,
things like using `Box<..>` directly as an operand in `pr_info!()`
are impossible, which is less ergonomic compared to `Box` in Rust
std.

Therefore add `impl Display` for `Box`.

Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://github.com/Rust-for-Linux/linux/issues/1126
Signed-off-by: Guangbo Cui <2407018371@qq.com>
---
Changes in v3:
- Update `fmt` implementation to clarify that it does not call itself infinitely.
- Link to v2: https://lore.kernel.org/rust-for-linux/tencent_F71CE9D125A8C6191D8CF95B3A4F3BB2F506@qq.com
Changes in v2:
- Add missing tag: Suggested-by.
- Update the patch title and the changelogs.
- Link to v1: https://lore.kernel.org/rust-for-linux/tencent_CA5A5D6268F0D1419BAFA6AFB4EB5A37920A@qq.com

 rust/kernel/alloc/kbox.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
index d69c32496..a496a866d 100644
--- a/rust/kernel/alloc/kbox.rs
+++ b/rust/kernel/alloc/kbox.rs
@@ -427,6 +427,16 @@ fn deref_mut(&mut self) -> &mut T {
     }
 }
 
+impl<T, A> fmt::Display for Box<T, A>
+where
+    T: ?Sized + fmt::Display,
+    A: Allocator,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        <T as fmt::Display>::fmt(&**self, f)
+    }
+}
+
 impl<T, A> fmt::Debug for Box<T, A>
 where
     T: ?Sized + fmt::Debug,
-- 
2.34.1