Cause is supported in error_chain!

[sfackler]

No description provided.

[Yamakaky]

Thanks!

[Arnavion]

Is it really supported? Error::cause() always returns either the next_error set in State via chain_err, or the wrapped foreign error. Neither of those appear to be be overriddable with custom cause()

[sfackler]

That's weird. The macro syntax definitely allows a cause(...)....

[Arnavion]

Yes, because quick_error supports it. But error_chain doesn't do anything with it since it has its own codegen.

[Arnavion]

Simple repro:

#[macro_use]
extern crate error_chain;

error_chain! {
	errors {
		IO(e: ::std::io::Error) {
			cause(e)
		}
	}
}

fn run() -> Result<()> {
	let x = Error::from(ErrorKind::IO(::std::io::Error::from_raw_os_error(1)));
	assert!(::std::error::Error::cause(&x).is_none());

	let y =
		Err::<(), _>(::std::io::Error::from_raw_os_error(1))
		.chain_err(|| ErrorKind::Msg("Msg".to_string()))
		.unwrap_err();
	assert!(::std::error::Error::cause(&y).is_some());

	Err(x) // Will not print "Caused by:"
	// Err(y) // Will print "Caused by:"
}

quick_main!(run);

[Yamakaky]

Oops, you are right, i should revert this commit.