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a69c2630f9
This does a few things: * Replaces the single `TypeId` in the `FacetTypeInfo` struct with a vector of `InterfaceId`, `SpecificId` pairs (sorted in id order) representing the set of interface requirements of the facet type. This will later be used to support facet types with multiple interface requirements (as in `I & J` or `I where .Self impls J`). * Replace `InterfaceType` instructions (used as the type of an `InterfaceDecl` instruction) with `FacetType` instructions (introduced in #4460) with a (newly introduced) `FacetTypeFromInterface()` function. * Replace code that consumed `InterfaceType` values with code that consumed `FaceType` values. I've generally left the assumption in the code that it is dealing with a single interface, using the (newly introduced) `FacetTypeInfo::TryAsSingleInterface`, and producing an error otherwise. There isn't yet support for the `&` operator or `where .Self impls`, so this is generally a good assumption for now, except you can get a facet type with no associated interfaces from a `type where`... expression. In some cases, the facet type value is pulled from the evaluation of an `InterfaceDecl` instruction, where the single interface assumption will hold permanently. * Some related cleans up: nicer stringification and formatting of facet types, suppression of some errors when there already was an error. There is still a lot left to do, including: * Type `type` should be a facet type with a reserved id, replacing the built-in instruction. * Code using `TryAsSingleInterface` should generally be upgraded to handle more than (or less than) one interface. Name lookup should be particularly exciting. * Operator `&` should be defined on facet types, unioning their interface and other requirements. * Requirements from a `where` clause don't do anything yet. * Impls and impl lookup need to resolve facet types, and do things like determine if all the associated constants are given values. --------- Co-authored-by: Josh L <josh11b@users.noreply.github.com> Co-authored-by: Geoff Romer <gromer@google.com>