Make Debug impl for ArcShift be idiomatic rust

arcshift/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.4.3
+
+Fix Debug impl of ArcShift, so that it honors "{:#?}" format strings.
+
 ## 0.4.2
 
 Support rust 1.75 (0.4.1 regressed to require newer rust).

arcshift/src/lib.rs

@@ -413,7 +413,9 @@ where
     T: Debug,
 {
     fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
-        write!(f, "ArcShift({:?})", self.shared_non_reloading_get())
+        f.debug_tuple("ArcShift")
+            .field(&self.shared_non_reloading_get())
+            .finish()
     }
 }
 

arcshift/src/tests.rs

@@ -17,9 +17,9 @@ use std::hint::black_box;
 use std::mem::MaybeUninit;
 use std::string::ToString;
 use std::sync::atomic::AtomicUsize;
-use std::thread;
 use std::time::Duration;
 use std::vec;
+use std::{format, thread};
 
 mod custom_fuzz;
 pub(crate) mod leak_detection;
@@ -2656,6 +2656,26 @@ fn simple_threading_try_into_inner3() {
     });
 }
 
+#[test]
+fn check_debug_impls() {
+    #[derive(Debug)]
+    struct Sample {
+        x: u32,
+        y: bool,
+    }
+
+    let x = ArcShift::new(Sample { x: 42, y: false });
+    let weak = ArcShift::downgrade(&x);
+
+    assert_eq!(format!("{:?}", x), "ArcShift(Sample { x: 42, y: false })");
+    assert_eq!(format!("{:?}", weak), "ArcShiftWeak(..)");
+    assert_eq!(
+        format!("{:#?}", x),
+        "ArcShift(\n    Sample {\n        x: 42,\n        y: false,\n    },\n)"
+    );
+    assert_eq!(format!("{:#?}", weak), "ArcShiftWeak(..)");
+}
+
 /*
 This does not compile, nor should it compile.
 ArcShift<T:'a> must be invariant in 'a.