nightly-2017-04-30 ICE regression - thread 'rustc' panicked at 'assertion failed: !unsize'

[frewsxcv]

https://github.com/PistonDevelopers/image currently doesn't compile. trying to minimize right now.

[est31]

Dupe of #41604, fixed by #41651

[Mark-Simulacrum]

Thanks! This is a duplicate of #41604.