Implement Debug for ErrorChainIter

Fixes  #169.

Author: ahmedcharles

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Unreleased
 
-- [Rename `ChanedError::display` to `display_chain`](https://github.com/brson/error-chain/issues/180)
+- [Implement `Debug` for `ErrorChainIter`](https://github.com/brson/error-chain/issues/169)
+- [Rename `ChainedError::display` to `display_chain`](https://github.com/brson/error-chain/issues/180)
 - [Add a new method for `Error`: `chain_err`.](https://github.com/brson/error-chain/pull/141)
 - [Allow `chain_err` to be used on `Option<T>`](https://github.com/brson/error-chain/pull/156)
 - [Add support for creating an error chain on boxed trait errors (`Box<Error>`)](https://github.com/brson/error-chain/pull/156)

src/lib.rs

@@ -493,6 +493,7 @@ pub use quick_main::ExitCode;
 #[cfg(feature = "example_generated")]
 pub mod example_generated;
 
+#[derive(Debug)]
 /// Iterator over the error chain using the `Error::cause()` method.
 pub struct ErrorChainIter<'a>(pub Option<&'a error::Error>);
 

tests/tests.rs

@@ -358,6 +358,7 @@ mod foreign_link_test {
     fn iterates() {
         let chained_error = try_foreign_error().err().unwrap();
         let mut error_iter = chained_error.iter();
+        assert!(!format!("{:?}", error_iter).is_empty());
         assert_eq!(format!("{}", ForeignError { cause: ForeignErrorCause {} }),
                    format!("{}", error_iter.next().unwrap()));
         assert_eq!(format!("{}", ForeignErrorCause {}),