Merge pull request #375 from dtolnay/unsized

Support dynamically sized field in error

src/display.rs

@@ -13,7 +13,7 @@ pub trait AsDisplay<'a>: Sealed {
 
 impl<'a, T> AsDisplay<'a> for &T
 where
-    T: Display + 'a,
+    T: Display + ?Sized + 'a,
 {
     type Target = &'a T;
 
@@ -44,7 +44,7 @@ impl<'a> AsDisplay<'a> for PathBuf {
 
 #[doc(hidden)]
 pub trait Sealed {}
-impl<T: Display> Sealed for &T {}
+impl<T: Display + ?Sized> Sealed for &T {}
 #[cfg(feature = "std")]
 impl Sealed for Path {}
 #[cfg(feature = "std")]

tests/test_path.rs

@@ -22,6 +22,13 @@ enum EnumPathBuf {
     Read(PathBuf),
 }
 
+#[derive(Error, Debug)]
+#[error("{tail}")]
+pub struct UnsizedError {
+    pub head: i32,
+    pub tail: str,
+}
+
 fn assert<T: Display>(expected: &str, value: T) {
     assert_eq!(expected, value.to_string());
 }