This is part of the ongoing renaming of the equality traits. See #12517 for more
details. All code using Eq/Ord will temporarily need to move to Partial{Eq,Ord}
or the Total{Eq,Ord} traits. The Total traits will soon be renamed to {Eq,Ord}.
cc #12517
[breaking-change]
`TotalEq` is now just an assertion about the `Eq` impl of a
type (i.e. `==` is a total equality if a type implements `TotalEq`) so
the extra method is just confusing.
Also, a new method magically appeared as a hack to allow deriving to
assert that the contents of a struct/enum are also TotalEq, because the
deriving infrastructure makes it very hard to do anything but create a
trait method. (You didn't hear about this horrible work-around from me
:(.)
The removed test for issue #2611 is well covered by the `std::iterator`
module itself.
This adds the `count` method to `IteratorUtil` to replace `EqIter`.
Allow a deriving instance using the generic code to short-circuit for
any non-matching enum variants (grouping them all into a _ match),
reducing the number of arms required. Use this to speed up the Eq &
TotalEq implementations.
