Implement Debug for EncodeWide

library/std/src/sys_common/mod.rs

@@ -15,7 +15,6 @@
 //! Progress on this is tracked in #84187.
 
 #![allow(missing_docs)]
-#![allow(missing_debug_implementations)]
 
 #[cfg(test)]
 mod tests;

library/std/src/sys_common/wtf8.rs

@@ -1049,6 +1049,23 @@ impl Iterator for EncodeWide<'_> {
 #[stable(feature = "encode_wide_fused_iterator", since = "1.62.0")]
 impl FusedIterator for EncodeWide<'_> {}
 
+#[stable(feature = "encode_wide_debug", since = "CURRENT_RUSTC_VERSION")]
+impl fmt::Debug for EncodeWide<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        struct CodeUnit(u16);
+        impl fmt::Debug for CodeUnit {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                write!(f, "{:#06X}", self.0)
+            }
+        }
+
+        write!(f, "EncodeWide(")?;
+        f.debug_list().entries(self.clone().map(CodeUnit)).finish()?;
+        write!(f, ")")?;
+        Ok(())
+    }
+}
+
 impl Hash for CodePoint {
     #[inline]
     fn hash<H: Hasher>(&self, state: &mut H) {

library/std/src/sys_common/wtf8/tests.rs

@@ -574,6 +574,17 @@ fn wtf8_encode_wide_size_hint() {
     assert!(iter.next().is_none());
 }
 
+#[test]
+fn wtf8_encode_wide_debug() {
+    let mut string = Wtf8Buf::from_str("aé ");
+    string.push(CodePoint::from_u32(0xD83D).unwrap());
+    string.push_char('💩');
+    assert_eq!(
+        format!("{:?}", string.encode_wide()),
+        r#"EncodeWide([0x0061, 0x00E9, 0x0020, 0xD83D, 0xD83D, 0xDCA9])"#
+    );
+}
+
 #[test]
 fn wtf8_clone_into() {
     let mut string = Wtf8Buf::new();