This reverts commit 00130cff.

As mentioned in a regression report[1], this caused a notable amount
of breakage.  Because there's a plan to mitigate[2] this type of
breakage, I'm reverting this until then.

[1]: https://internals.rust-lang.org/t/new-crater-reports-1-1-stable-vs-beta-2015-07-10-and-nightly-2015-07-10/2358
[2]: https://github.com/rust-lang/rfcs/pull/1193