The implementation essentially desugars during type collection and AST
type conversion time into the parameter scheme we have now. Only fully
qualified names--e.g. `<T as Foo>::Bar`--are supported.
I ended up altering the semantics of Json's PartialOrd implementation.
It used to be the case that Null < Null, but I can't think of any reason
for an ordering other than the default one so I just switched it over to
using the derived implementation.
This also fixes broken `PartialOrd` implementations for `Vec` and
`TreeMap`.
RFC: 0028-partial-cmp
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]
* `Ord` inherits from `Eq`
* `TotalOrd` inherits from `TotalEq`
* `TotalOrd` inherits from `Ord`
* `TotalEq` inherits from `Eq`
This is a partial implementation of #12517.
This code fits better in check because it is checking that the impl
matches the interface. This allows us to avoid the awkward constructions
that lazilly collect traits and so forth. It also permits us to make
use of the results of variance inference.
It will be simpler to implement only one method for Ord, while we also
allow implementing all four Ord methods for semantics or performance
reasons.
We only supply three default methods (and not four), because don't have
any nice error reporting for the case where at least one method must be
implemented, but it's arbitrary which.
But note that default methods still don't work cross-crate (see #2794) --
this just makes it so that when a method is missing in a cross-crate impl,
the right error message gets printed.
Closes#3344
