RetainMut
Trait that provides retain_mut
method.
This method is basically the same as Vec::retain
,
but it gives mutable borrow to the predicate function.
This was probably a historical mistake in Rust library,
that retain
should do this at the very beginning.
See rust-lang/rust#25477.
It currently only implements retain_mut
for Vec
.
We may implement it for more collection types in the future.