rust-lang/rust — pull request #19520 by csouth3 (2014-12-04 09:14:55+00:00)
Title: `DerefMut` should be `for Sized?`

Right now, `DerefMut` is not `for Sized?`, so you can't impl `DerefMut for Foo` where `Foo` is unsized. However, there is no reason that it can't be `for Sized?`, so this pull request fixes the issue.

Closes #19493.