Still to do:
* Represent facet type values in a canonical form
* Produce & consume facet type values instead of interface values
* `type` should be associated with a canonical facet type value
* Support `&` on facet type values
* Type check and enforce requirements in facet types
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
With this, we now check:
* The left argument to `where` is a facet type
* The right argument of a rewrite (`=`) requirement converts to the type
of the left argument.
* The left argument of an `impls` requirement is a type and the right
argument is a facet type.
No checking is done for `==` constraints yet.
In addition, make the "is facet type" query into its own function and
fix some comments noticed as part of this change.
This change reveals that accessing the members of a facet, like `.Self`,
isn't doing the right thing, and will have to be fixed in a follow-on
PR. Some tests have been adjusted or disabled as a result.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
The check stage now produces SemIR instructions to represent a `where`
clause. It still does not check types.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Right now, there is no checking of `where` requirements. The result of a
where expression is just the type on the left-hand side. It does now
introduce `.Self` so that it is available in expressions on the
right-hand side, in addition to designators corresponding to the members
of type on the left-hand side. Note, though, that diagnostics could
still be improved significantly.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Includes support for the `impls`, `=`, and `==` requirement operators to
the right of a `where`, but `and` to allow multiple requirements is
still a TODO.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
These appear in `where` clauses, as in:
```
U:! InterfaceB where .C = Vector(.D)
V:! type where Vector(.Self) impls Sortable
```
`.Self` can additionally appear in type expressions in a binding pattern
such as `T:! InterfaceA(.Self)`.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
josh11bandJosh L
Richard Smith
