They are still present as part of the borrow check.

this also adds a derived Eq, TotalEq, Ord and TotalOrd along with
removing the useless constructor

part of #3853

Fix a laundry list of warnings involving unused imports that glutted
up compilation output.  There are more, but there seems to be some
false positives (where 'remedy' appears to break the build), but this
particular set of fixes seems safe.

Adds documentation for various things that I understand.
Adds #[allow(missing_doc)] for lots of things that I don't understand.

This isn't needed semantically, and it's the wrong case to optimize for.

This only changes the directory names; it does not change the "real"
metadata names.

fail!() used to require owned strings but can handle static strings
now. Also, it can pass its arguments to fmt!() on its own, no need for
the caller to call fmt!() itself.

Added unit test to prevent similar mistakes from happening again. The
previous method was wrong because it dereferenced a pointer to a void type to
match on the result. No self pointer was needed, and the correct method
signature took the self value by value.

In this commit I added a useful utility type, named Void, that encapsulates the
doable but annoying job of creating an uninhabited type. As well, a function on
that type, named absurd, was created which is useful for ignoring the result of
matching on that type. No unit tests were created because it is not possible to
create an instance of this type to test the usage of.

This type is useful because it is like NonCopyable in that it can be used to
create a type with special characteristics without special bloat. For instance,
instead of typing pub struct PhantomType { priv contents : () } for each void
type one may want to use one can simply type pub struct PhantomType (Void);.
This type make such special cases much easier to write.

correct handling of moves for struct-record update.

Part of #3678.  Fixes #2828, #3904, #4719.