This started out of the blue, I have my nightly version pegged so I don't have to deal with things that suddenly stops working, however this error just appeared out of nowhere when building my rust program.
/home/benjamin/.cargo/git/checkouts/diesel-6e3331fb3b9331ec/master/diesel_codegen/src/lib.rs:1:43: 1:91 error: #[feature] may not be used on the stable release channel
/home/benjamin/.cargo/git/checkouts/diesel-6e3331fb3b9331ec/master/diesel_codegen/src/lib.rs:1 #![cfg_attr(not(feature = "with-syntex"), feature(rustc_private, plugin_registrar, quote))]
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
error: aborting due to previous error
error: Could not compile `diesel_codegen`.
This affects stable, beta, nightly for me. However Travis is just fine, so I thought it might have been cargo going crazy, so I uninstall rustup (rustup self uninstall) then reinstall rustup and download stable, beta, nightly, & nightly-2016-05-08. No cigar, still wouldn't work. After much searching I decided to ask the community for help, since this issue makes it impossible for me to test locally.
That's the wrong version of Rust. It should say something like rustc 1.10.0-nightly (0123abcd 2016-05-08) It looks like you have another installation of Rust 1.8.0 somewhere on your system, and it's earlier in your $PATH than the one installed by rustup. Running which rustc should help determine where it is.