Make Debug instances behave like those for slices

src/arrayvec.rs

@@ -1712,20 +1712,7 @@ where
 {
   #[allow(clippy::missing_inline_in_public_items)]
   fn fmt(&self, f: &mut Formatter) -> core::fmt::Result {
-    write!(f, "[")?;
-    if f.alternate() && !self.is_empty() {
-      write!(f, "\n    ")?;
-    }
-    for (i, elem) in self.iter().enumerate() {
-      if i > 0 {
-        write!(f, ",{}", if f.alternate() { "\n    " } else { " " })?;
-      }
-      Debug::fmt(elem, f)?;
-    }
-    if f.alternate() && !self.is_empty() {
-      write!(f, ",\n")?;
-    }
-    write!(f, "]")
+    <[A::Item] as Debug>::fmt(self.as_slice(), f)
   }
 }
 
@@ -2056,4 +2043,26 @@ mod test {
     av.retain_mut(|&mut x| x % 2 == 0);
     assert_eq!(av.len(), 0);
   }
+
+  #[cfg(feature = "alloc")]
+  #[test]
+  fn array_like_debug() {
+    #[derive(Debug, Default, Copy, Clone)]
+    struct S {
+      x: u8,
+      y: u8,
+    }
+
+    use core::fmt::Write;
+
+    let mut ar: [S; 2] = [S { x: 1, y: 2 }, S { x: 3, y: 4 }];
+    let mut buf_ar = alloc::string::String::new();
+    write!(&mut buf_ar, "{ar:#?}");
+
+    let av: ArrayVec<[S; 2]> = ArrayVec::from(ar);
+    let mut buf_av = alloc::string::String::new();
+    write!(&mut buf_av, "{av:#?}");
+
+    assert_eq!(buf_av, buf_ar)
+  }
 }

src/slicevec.rs

@@ -890,20 +890,7 @@ where
 {
   #[allow(clippy::missing_inline_in_public_items)]
   fn fmt(&self, f: &mut Formatter) -> core::fmt::Result {
-    write!(f, "[")?;
-    if f.alternate() && !self.is_empty() {
-      write!(f, "\n    ")?;
-    }
-    for (i, elem) in self.iter().enumerate() {
-      if i > 0 {
-        write!(f, ",{}", if f.alternate() { "\n    " } else { " " })?;
-      }
-      Debug::fmt(elem, f)?;
-    }
-    if f.alternate() && !self.is_empty() {
-      write!(f, ",\n")?;
-    }
-    write!(f, "]")
+    <[T] as Debug>::fmt(self.as_slice(), f)
   }
 }
 
@@ -1067,3 +1054,30 @@ where
     write!(f, "]")
   }
 }
+
+#[cfg(test)]
+mod test {
+  use super::*;
+
+  #[cfg(feature = "alloc")]
+  #[test]
+  fn array_like_debug() {
+    #[derive(Debug, Default, Copy, Clone)]
+    struct S {
+      x: u8,
+      y: u8,
+    }
+
+    use core::fmt::Write;
+
+    let mut ar: [S; 2] = [S { x: 1, y: 2 }, S { x: 3, y: 4 }];
+    let mut buf_ar = alloc::string::String::new();
+    write!(&mut buf_ar, "{ar:#?}");
+
+    let av: SliceVec<S> = SliceVec::from(&mut ar);
+    let mut buf_av = alloc::string::String::new();
+    write!(&mut buf_av, "{av:#?}");
+
+    assert_eq!(buf_av, buf_ar)
+  }
+}

src/tinyvec.rs

@@ -1676,20 +1676,7 @@ where
 {
   #[allow(clippy::missing_inline_in_public_items)]
   fn fmt(&self, f: &mut Formatter) -> core::fmt::Result {
-    write!(f, "[")?;
-    if f.alternate() && !self.is_empty() {
-      write!(f, "\n    ")?;
-    }
-    for (i, elem) in self.iter().enumerate() {
-      if i > 0 {
-        write!(f, ",{}", if f.alternate() { "\n    " } else { " " })?;
-      }
-      Debug::fmt(elem, f)?;
-    }
-    if f.alternate() && !self.is_empty() {
-      write!(f, ",\n")?;
-    }
-    write!(f, "]")
+    <[A::Item] as Debug>::fmt(self.as_slice(), f)
   }
 }
 

tests/tinyvec.rs

@@ -499,3 +499,25 @@ fn TinyVec_std_io_write() {
   assert!(tv.is_heap());
   assert_eq!(tv, tiny_vec![b'f', b'o', b'o', b'b', b'a', b'r']);
 }
+
+#[cfg(feature = "alloc")]
+#[test]
+fn TinyVec_array_like_debug() {
+  #[derive(Debug, Default, Copy, Clone)]
+  struct S {
+    x: u8,
+    y: u8,
+  }
+
+  use core::fmt::Write;
+
+  let mut ar: [S; 2] = [S { x: 1, y: 2 }, S { x: 3, y: 4 }];
+  let mut buf_ar = alloc::string::String::new();
+  write!(&mut buf_ar, "{ar:#?}");
+
+  let av: TinyVec<[S; 2]> = TinyVec::from(ar);
+  let mut buf_av = alloc::string::String::new();
+  write!(&mut buf_av, "{av:#?}");
+
+  assert_eq!(buf_av, buf_ar)
+}