[RFC 5/5] sample: rust: print: Add sampe code for Arc printing

[Boqun Feng <boqun.feng@gmail.com>]

This both demonstrates the usage of different print format in Rust and
serves as a selftest for the `Display` and `Debug` implementation of
`Arc` and its friends.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
 samples/rust/rust_print.rs | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/samples/rust/rust_print.rs b/samples/rust/rust_print.rs
index 8b39d9cef6d1..165a8d7b1c07 100644
--- a/samples/rust/rust_print.rs
+++ b/samples/rust/rust_print.rs
@@ -15,6 +15,30 @@ module! {
 
 struct RustPrint;
 
+fn arc_print() -> Result {
+    use kernel::sync::*;
+
+    let a = Arc::try_new(1)?;
+    let b = UniqueArc::try_new("hello, world")?;
+
+    // Prints the value of data in `a`.
+    pr_info!("{}", a);
+
+    // Uses ":?" to print debug fmt of `b`.
+    pr_info!("{:?}", b);
+
+    let a: Arc<&str> = b.into();
+    let c = a.clone();
+
+    // Uses `dbg` to print, will move `c`.
+    dbg!(c);
+
+    // Prints debug fmt with pretty-print "#" and number-in-hex "x".
+    pr_info!("{:#x?}", a);
+
+    Ok(())
+}
+
 impl kernel::Module for RustPrint {
     fn init(_module: &'static ThisModule) -> Result<Self> {
         pr_info!("Rust printing macros sample (init)\n");
@@ -43,6 +67,8 @@ impl kernel::Module for RustPrint {
         pr_cont!(" is {}", "continued");
         pr_cont!(" with {}\n", "args");
 
+        arc_print()?;
+
         Ok(RustPrint)
     }
 }
-- 
2.39.1