When performing impl lookup for `Core.Copy` for a C++ class type, look
for a copy constructor. If we find one, synthesize an impl witness that
calls the constructor.
This adds initial support for impl lookup to delegate to the C++ interop
logic for queries involving C++ types. For now, we don't implement the
rules from #6166 that compare a synthesized type structure for the C++
impl against the best Carbon type structure, but the framework for
building that support is established here.
Currently there is no caching of the lookup here, and we build unique
`ImplWitnessTable`s for each lookup, which leads to each impl lookup
producing a distinct facet value. This results in some errors in generic
contexts; this will be addressed in follow-up changes. This PR aims only
to support the non-generic case.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
When forming an IdentifiedFacetType, we collect interfaces named by
require decls in named constraints that the facet type refers to. These
interfaces come with a specific, but the require decl is inside an named
constraint which may be generic. So we need the specific being applied
to the containing named constraint to also be applied to the require
decl and its target interfaces.
This uncovered that the facet type in require decls was not being
imported correctly, as it was not being attached to the require decl's
generic. This is fixed by making import of RequireImplsDecl multiphase,
so that the decl instruction exists before we resolve the facet type
within it. And by pointing the generic importing machinery to the
RequireImplsDecl, and from there to the RequireImpls structure to get
the generic id.
Then `ImplStore::GetOrAddLookupBucket` can use an IdentifiedFacetType to
correctly get the interface being impl'd, both in the local and the
imported named constraint case. Which allows us to correctly diagnose
redeclarations in the impl file of an impl of an interface through a
named constraint. And to correctly _not_ diagnose them when the specific
in the generic named constraint differs from other decls.
There are two uses I'm not converting here, that seem to want the
"shortest" behavior. For everything else, I'm going to `zip_equal` since
it's more restrictive.
I wish `zip` were named `zip_shortest`.
Proposal #5168 defines when a facet type must be identified or complete,
and what it means for an interface and a named constraint to be
identified or complete. This updates the toolchain to match the
requirements.
This implements identification of a facet type to require completed
named constraints and to include any interfaces from named constraints
into the resulting IdentifiedFacetType.
To complete a facet type, each interface in the IdentifiedFacetType, and
any interface named though a require declaration from them, must be
complete.
This requires declared FacetTypes to hold NamedConstraintIds (along with
a specific) that are named in an extend or impls requirement. We add
support to stringify and formatter to display the named constraints in
the facet type, and special case when a facet type contains a single
extend named constraint, like we did for a single extend interface.
This means that `RequireIndentifiedFacetType` can now fail, if the facet
type contains a forward-declared named constraint. Add the appropriate
diagnostics for each call to this function, and note the ones that
should change to `RequireCompleteFacetType` in the future with TODOs.
We also add tests for using facet types that can or can't be identified,
or completed, with named constraints in them.
`ImplWitnessTablePlaceholder` is the only non-type singleton instruction
(`ErrorInst` is a type; while `ImplWitnessTablePlaceholder` exposes
`TypeInstId`, it's only used as an `InstId`).
In order to allow simpler handling of singleton instructions, replace
`ImplWitnessTablePlaceholder::TypeInstId` uses with
`InstId::ImplWitnessTablePlaceholder`. Since the placeholder instruction
was never evaluated, this has no significant effect on behavior.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
When deducing arguments for generic parameters of an `impl`, the
deduction calls `Convert` on the input arguments. Often, the input
argument is a facet, and needs to be converted to a type via
FacetAccessType in order to produce a different facet. These
instructions end up being added to the semir, but only their constant
values are needed for the resulting specific returned from Deduce.
In the best case, these extra instructions are just noise in the semir,
or they just cause instruction names to get differentiated with larger
suffixes.
In the worst case, these extra instructions contain references to
instructions from a generic context, and leak them out of that generic
context and into another. In particular, when importing a
LookupImplWitness instruction, the re-evaluation of it can do deduce
(when the lookup is against a generic `impl`). The instructions created
in Deduce are not part of the import, and end up referring to imported
instructions from the local context, which leads to confusion in the
toolchain, and can crash.
The `import_self_specific.carbon` test demonstrates this. It causes the
`I.F` function to be imported from the `I` interface when building the
witness table for the `impl`. Doing so imports the specific of `C` which
includes a LookupImplWitness for `Self.Accoc` in `I`. The `Self` is a
BindSymbolicName with generic binding index 0, in `I`. When Convert
creates instructions in the generic `impl forall D`, however, they end
up referencing and including this BindSymbolicName into its eval block.
But the generic binding 0 in the `impl` is a very different thing (a
value of type `E`). This confusion leads to crashes.
In trying to have types implicitly define `impl Self as Destroy`, I'm
wanting to use standard impl declaration support. For example, this
should produce more consistent errors if someone writes code that would
conflict with the generated impl. I'm also concerned, with the
complexity involved, that I'd get something wrong if I tried to write a
divergent implementation.
I'm only factoring out the start of the declaration. Right now the
finishing portion seems much simpler and lower risk to duplicate; I may
also factor it out separately. But either way, I think `StartImplDecl`
here is high churn risk due to its size (`CheckConstraintIsInterface` I
also expect to be used).
Undo changes that were meant to prevent use of a reference into
`ValueStore` after being invalidated. After #5576, the `ValueStore`
makes such references stable, so there's no need to worry about
invalidation.
When we fill the witness table with errors, set the witness id to an
error too, which signals to impl lookups to not use the impl.
Make the use of the `Impl` from the store more consistent once it's been
added to the store (or known to be there already).
Remove calls to `InstStore::GetLocId()` to build a LocId from an InstId
now that they can be constructed directly from the InstId. Most uses of
LocId are just plumbing, so this does not affect them. However places
that want to look inside the LocId do not want to work with the InstId
form. In these places, introduce `InstStore::GetResolvedLocId()` which
converts a LocId (or an InstId as an optimization) into a LocId which is
not backed by an InstId. These locations can be printed (they have a
line and column when they are a NodeId), they can have flags added to
them (`ToImplicit`, `ToTokenOnly`), they can be converted to an
underlying ImportIRInstId, or they may be `None`.
`Dump()` is made to print a resolved location instead of printing the
InstId in the location, since (at least in my experience) the resolved
location is what is interesting in debugging, and this saves manual
`MakeInstId` steps in the debugger every time a location is of interest.
The LocId constructor from InstId is made `explicit` to add clarity to
function calls passing an `inst_id` now directly instead of calling
`context.insts().GetLocId(inst_id)`. To avoid needing to construct
`SemIR::LocId(...)` explicitly in all cases though, the diagnostics code
in Check uses `DiagnosticLocId` as its template parameter which accepts
InstId as well and does the construction of LocId from it.
Because LocId now requires an explicit construction from InstId, any
callers to `AddInst()` functions will have to explicitly convert to
LocId if they had an InstId, but not if they pass a NodeId. To make this
difference clear to callers, we `requires` that the input type can be
converted to LocId. This ensures that passing an InstId results in an
error at the callsite where the InstId is passed, instead of generating
a compiler error when trying to construct `LocIdAndInst` inside
`AddInst()`, which is less clear about what went wrong and doesn't seem
entirely intentional.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
These constant instructions are all TypeInstId already in their type,
and this makes their names match.
Change the name of MakeSingletonInstId as well and update its comment.
We frequently want to operate on singletons. Per discussion, drop
`Singleton` to make the code shorter.
This started off as wanting to write `inst_id.is_error()`, but the
dependency relationship between ids.h and singleton_insts.h would
require some kind of delayed evaluation to allow the implementation to
remain in headers (which I suspect is helpful to have for inlining). I
could have added something like `IsErrorInst`, forward declared in ids.h
and defined in singleton_insts.h (which would always be included by
typed_insts.h), but the template approach felt like a decent balance
between (a) removing the boilerplate `::SingletonInstId`, (b)
understandability, (c) still visually mirroring if we immediately return
a singleton, and (d) flexibility for more than just `ErrorInst`. But TBH
I'd probably still have written `is_error()` if it didn't require
addressing the cross-header cycle.
Then I tried `SemIR::InstId::Is<SemIR::ErrorInst>`, which generally
worked with types but generated the complaint that it didn't shorten
*all* singleton uses. So pulling back on `::Is`, and instead just
dropping `Singleton`.
This allows us to import the table for a given impl only once, while we
can import many ImplWitness instructions with different specifics for a
generic impl.
For example in convert_facet_value_to_narrowed_facet_type.carbon we see
that a single witness table is imported for the BitAnd interface, with
multiple witnesses (for different specifics) imported and sharing the
same table.
The ImplWitnessTable now contains a back-link to the Impl the witness is
for, allowing inst namer to name that interface in the textual semir,
and allowing the interface to be found when debugging from a witness.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
While facets may come with a rewrite for an associated constant, they
are symbolic. A final impl has the ability to provide a concrete value
instead, which allows generic code to use the concrete value in place of
the associated constant's (fully qualified) name.
For instance, instead of `I.Type`, the concrete type `()` can be used if
there is an `impl final [T:! type] T as I where .Type = ()` impl.
This does not yet cache the result of the lookups.
Depends on https://github.com/carbon-language/carbon-lang/pull/5255
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Instead of using None, use an explicit ImplWitnessTablePlaceholder in
the witness table for entries that have not yet been populated, to aid
debugging. This would ensure they would show up very clearly in the
SemIR. This uncovered some `<invalid>` in the SemIR under erroneous
conditions that have now been turned into `<error>`.
Add the ImplWitnessAssociatedConstant instruction which wraps the
canonical instruction found from the constant value of the rewrite
constraint. This ensures that we have an instruction inside the eval
block for a generic impl declaration for each rewrite constraint's
value, which allows Subst to be performed to rewrite the symbolic
constant of the ImplWitnessAssociatedConstant instruction to associate
it with the generic. This will prevent the otherwise orphaned symbolic
constant of the rewrite's value from being used which can not have a
specific applied to them.
While applying the new insts in InitialFacetTypeImplWitness(), rearrange
the function to use less nesting. And avoid using entity names from
imported instructions (as we found is not effective in deduce.cpp) and
use a local instruction by going through the constant value.
This PR is part of the effort to allow a rewrite to name a generic
parameter, such as `impl forall [T:! type] T as Z where .X = T`, however
tests for this involve a final impl so that we can typecheck that the .X
value is a specific T, so the tests will come with that work. This piece
is split off because introducing new instructions causes a lot of SemIR
churn, and I wanted to get that done separately.
Implements some of the changes from proposal #5168.
* The data structure for complete facet types has been repurposed for
identified facet types. Identified facet types are now a concept in the
toolchain, but without named constraint support they are not
substantially different from incomplete facet types.
* Identified facet types keep the list of required specific interfaces
in sorted order, for efficiency improvements in impl lookup. Found
another way to identify the interface to impl (or number of impls if not
1).
* Forward `impl` declarations of identified but incomplete facet types
are allowed unless the facet type has rewrites. An incomplete facet type
with rewrites is already either an error or has more than one interface
and so can't be implemented, so this case can't be exercised very well
yet.
* Forward `impl` declarations of interface without rewrites use a
placeholder inst block for the witness.
* Changed some machinery to use RequireIdentifiedFacetType to access the
interfaces of the facet type so we only need to add support for
expanding named constraints into interfaces in one place.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Dana Jansens <danakj@orodu.net>
I was thinking about this after `seq` changes in #5182, and looked for
other uses that might be replaceable. Here's the resulting cleanup
around `seq`:
- Switch to `enumerate` or `zip` when possible.
- `int _` -> `auto _` (it's typically a `size_t`, but there's no reason
to cast when unused)
- Fix a case of cast style `(size_t)...` -> `static_cast<size_t>(...)`
- Switch `(void)close_children_count` to `[[maybe_unused]]`
This allows the numbering of the parameters to match when checking for a
valid redeclaration. It also prepares us to produce the proper numbering
when generating a thunk.
This tripped over a lowering crash when a member function with self was
declared-but-not-defined, so that's why some test cases were updated to
have (empty) function definitions.
I'll follow-up with/look into a fix for the
self-declared-but-not-defined cases separately.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
There aren't remaining uses on `Context` other than `DiagnosticEmitter`
itself. I'm adding `SemIRLoc` because I feel odd about having both
`Carbon::Check::DiagnosticBuilder` and
`Carbon::DiagnosticEmitter<T>::DiagnosticBuilder`, but it seems
relatively little additional typing outside the handful of
`DiagnosticEmitter` uses on `Context` itself:
```
Context::DiagnosticEmitter
DiagnosticEmitter<SemIRLoc>
Context::DiagnosticBuilder
SemIRLocDiagnosticBuilder
Context::BuildDiagnosticFn
BuildSemIRLocDiagnosticFn
```
Also clean up #include's while I'm finishing here.
* Add `RequireCompleteFacetType` and `ResolveFacetTypeImplWitness` to
`check::Context`. Goal was to move code from `impl.cpp` (mostly) without
functional changes.
* Complete type information is cached with the facet type, and is stored
in a `complete_facet_types()` table.
* Main functional change is to diagnose attempts to use a rewrite
constraint on an associated function. Some existing diagnostics have
been updated.
* Remove `check::Context::RequireDefinedType`:
* For class types, use `RequireCompleteType`
* For facet types, use `RequireCompleteFacetType`
* Introduce a `SemIR::SpecificInterface` to hold an interface and
specific id pair.
* Keep the specific interface ids in the impl object.
* Avoid some extra copies in `Dump` functions.
* Future work missing from this PR:
* Resolving for member access or actions that require impl lookup.
* Resolving rewrites constraints that refer to non-concrete values.
* Any support for adding implied constraints that result from a `where`
clause (though TODOs have been added).
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Dana Jansens <danakj@orodu.net>
Currently it returns false which just ends typechecking. Instead handle
the error state later and avoid firing overlapping diagnostics in
'extend impl as'.
---------
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
This in particular uses free functions because it's likely to end up
more consistent with types (versus a wrapper object for InstStore).
Note, this is unlikely to have a performance impact, but if it does, we
can look into related approaches (and we've already discussed using
LTO).
Renames `PendingBlock::AddInst` to `PendingBlock::Add` because
`MakeElementAccessInst` expects the matching name to exist.
This creates a new check/type.h for most logic, and also moves some
functions to TypeStore in sem_ir/type.h. My approach for TypeStore is to
focus on moving the read-only functions there.
context.cpp is getting large, so I'm looking at a few ways to cut out
clusters of functions. This felt like a logical cluster of functions to
move to their own file.
Note I have two commits in this PR: one moving the functionality to a
new file, and one specifically changing TypeCompleter to use out-of-line
function implementations. This is to assist reviewability.
Based on [the lastest thinking on
#4672](https://github.com/carbon-language/carbon-lang/issues/4672#issuecomment-2606209281)
, require a full syntactic match for impl redeclaration, instead of
excluding the `where` restriction. This means no updates to the impl
witness on redeclaration, and no diagnostics that those updates are
consistent.
Not included in this PR, but will need to be done in the future:
* Support for assigning values to associated constants in the body of
the impl definition. This will require moving the checking that
non-function associated constants are set from the definition start to
definition end.
* Identify semantic redeclarations that are not syntactic matches to
give a failed redeclaration diagnostic. This should be done once we are
already identifying impl declarations with the same type structure in
order to require they be identified in an impl_priority/match_first
block.
* Merging of the functions in `check/impl.cpp` that are now always
called together.
Also add some test coverage of `where` parsing I developed in PR I've
now abandoned because of this new simplification of the impl
redeclaration semantics.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Benefits:
* Provide a proper API for accessing lookup information.
* Make assumptions on whether the result is poisoned or not and how we
can use `InstId` explicit.
* Allow safely reusing the `InstId` value for pointing to the poisoning
entity for poisoned results (in a future PR).
* Consolidate `LookupNameInExactScopeResult`, `std::pair<SemIR::InstId,
bool>` and part of `LookupResult`.
Part of #4622.
Add a full entity representation for associated constants, and build a
`Generic` object for them. This `Generic` is parameterized by the
enclosing `Self` type, allowing the use of `Self` within the type of the
associated constant to be supported.
When performing impl lookup for an associated constant, produce the type
with the provided self type substituted for its `Self` along with any
generic parameters of the interface.
Split the handling of associated constant declarations into two parts,
corresponding to the code before the `=`, and the code between the `=`
and `;` (if any). The former goes into the generic declaration region;
the latter into the generic definition region. This prepares us to
handle the default value for an associated constant, but for now we're
just storing the information and not actually using it.
Remove the entity type field from `assoc_entity_type`, because it's
almost unused and is an attractive nuisance -- it must necessarily be a
type in the generic scope of the associated constant rather than in the
scope of the instruction (because there is no `Self` anywhere else),
which means that it's hard to substitute into or derive meaning from.
See `toolchain/check/testdata/impl/assoc_const_self.carbon` for tests of
the new functionality; these used to cause the toolchain to crash.
High level, replacing `Id::Invalid` with `Id::None` and `Id::is_valid`
with `Id::has_value` for clarity, as discussed
[here](https://discord.com/channels/655572317891461132/655578254970716160/1331664574545395794).
The `IntId` refactoring is needed together with `AnyIdBase` because it's
also used with `ValueStore`.
Note, trying to be careful not to rewrite `EnumBase::InvalidIndex`, or
`is_valid` in general (e.g., `IdKind::is_valid`).
I've tried to sequence commits here:
1. Automatic replacements:
- `((?:Id|Index)(?: |::|\(|Base(?:\(|::)))Invalid((?:Index)?\W)` ->
`$1None$2`
- `<invalid>` -> `<none>`
- `InvalidNodeId` -> `NoneNodeId`
- `/\*invalid\*/` -> `/*none*/`
- `id((?:_|\(\))(?:\.|->))is_valid` -> `id$1has_value`
2. Manual edits:
- In `int.h` and `int_test.cpp`
- `IntT` has `is_value`, which I'm renaming to `is_embedded_value`.
- Manual edits to comments in this file.
- `AnyIdBase` and `IdBase`
- Declaration of `is_valid` -> `has_value`, `InvalidIndex` ->
`NoneIndex`.
- In `ids.h` and `ids.cpp`
- `is_valid` -> `has_value`
- `// An explicitly invalid ID.` -> `// An ID with no value.`; similar
for index
- Various math on `InvalidIndex` -> `NoneIndex`
- Various mentions of "valid" in comments
- In `value_store.h`, for `IdT::Invalid`, plus one comment
- In `impl.h` and `tokenized_buffer.h`, we had different initialization
of `::None` values (versus `ids.h` syntax) that I fixed manually.
- Spot checks to compile
- Particularly where `is_valid` replacements didn't catch spots due to
different naming.
3. Autoupdate tests
4. verbose.carbon (NOAUTOUPDATE)
5. Comment spot checks
Note there are probably other mentions of "Invalid" that should be swept
up, but I'd like to argue for merging and separating out remaining
cleanup since this is so sweeping (and likely to hit merge conflicts
from churn). We'll probably have lingering mentions of "invalid" for a
bit regardless, just because there are uses of "invalid" in non-Id APIs.
I believe `check_syntax` is already controlling the semantic vs
syntactic merge, added in #4149. Other parts of the TODO are clarified
per discussion. But this is tested, e.g. errors with the bool flipped:
```
impl i32 as I {
+ // CHECK:STDERR: method.carbon:[[@LINE+6]]:14: error: redeclaration syntax di
ffers here [RedeclParamSyntaxDiffers]
+ // CHECK:STDERR: fn F[self: i32](other: i32) -> i32 = "int.sadd";
+ // CHECK:STDERR: ^~~
+ // CHECK:STDERR: method.carbon:[[@LINE-7]]:14: note: comparing with previous
declaration here [RedeclParamSyntaxPrevious]
+ // CHECK:STDERR: fn F[self: Self](other: Self) -> Self;
+ // CHECK:STDERR: ^~~~
fn F[self: i32](other: i32) -> i32 = "int.sadd";
}
```
With this change, we now support impl of interfaces with non-function
associated constants.
Also:
* Make impl diagnostics use more consistent names
* Make some impl tests "no_prelude"
Still to do:
* Facet type resolution as a separate, reusable step
* Using the assigned values of associated constants (see
`fail_todo_use_assoc_const.carbon`)
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Change the implementation to use an explicit `is_poisoned` bit instead
of `InstId::PoisonedName` value.
Zero behavior change.
This would allow to more easily change the API to support accessing the
poisoning declaration so we can have better name poisoning diagnosis.
#4622
* Change `InterfaceWitness` -> `ImplWitness`
* Include a `SpecificId` in the `ImplWitness`. This allows the
`InstBlock` it contains to have its own identity, allowing it to be
changed as the impl is processed. Evaluation only updates the specific.
* Create the `ImplWitness` at the start of the impl definition. In the
future, this will be populated with the values of non-function
associated constants. For now, it starts full of invalid instruction
ids.
* Implements the model suggested in #4672 .
Note that the non-SemIR testdata changes are to these file:
* `toolchain/check/testdata/impl/lookup/fail_todo_undefined_impl.carbon`
* `toolchain/check/testdata/struct/import.carbon`
* `toolchain/check/testdata/tuple/import.carbon`
The last two are due to an import of generics bug exposed by this PR,
which will be fixed in a follow-on.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Also fix a bug in `Context::GetClassType` that previously tried to
complete the class type before returning it. That's not correct --
`GetCompleteTypeImpl` is only appropriate for cases where the type can
trivially be completed and completing it can't fail -- and led to
infinite recursion with this change because we would call `GetClassType`
when producing a diagnostic if completing that class type failed.
When a generic requires a symbolic type to be complete, add a new
`require_complete_type` instruction to the generic eval block. During
monomorphization of such an instruction, require that type to be
complete.
`ids.h` and `ids.cpp` are the manual edits, everything else is
search-and-replace.
The full list of things moved is:
- `TypeId::TypeType`
- `TypeId::AutoType`
- `TypeId::Error`
- `ConstantId::Error`
This is to unblock removing `InstId::Builtin*`.
* Rewrite constraints are stored in a facet type, substituted, imported,
and formatted.
* We now distinguish `.Self` from other symbolic bindings in two ways:
* `.Self` itself now has an invalid compile time binding index (since it
doesn't bind to any of the generic parameters). As a result, we no
longer need to create a generic region in `handle_where.cpp`.
* There is a new phase tracking values that are only symbolic because
they transitively depend on `.Self`. This allows us to give the result
of a `where` expression template phase as long as it doesn't use any
symbolic constants other than `.Self` or other designators.
* `AddConstant` has been removed from `check/context` since it was only
used from `eval`. This meant less plumbing of the phase change.
* Evaluation of `BindSymbolicName` now also performs substitution into
its type.
* Include a bit more information in some diagnostics.
* `StringifyTypeExpr` outputs rewrites, which required adding support
for associated entities as well.
* Associated entities now have an entity name set when importing.
* Adds tests for some interesting cases with rewrites and uses of
`.Self` mixed with other symbolic constants.
Still to do:
* There is no validation that any particular type satisfies rewrite
constraints.
* Access to members of a facet type do not see the rewritten values.
* Impls don't recognize whether associated constants have rewrites
setting their values.
* No support for resolving facet types.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
The new `FacetValue` instruction represents `C as I` for some type `C`
and facet type `I`. It is named `FacetValue` instead of just `Facet` to
parallel the `FacetType` instruction.
This PR uses this instruction represent the facet value `Self` in an
`impl` declaration. This instruction will be used in the future to also
support things like:
* `C as I` where `C` is a class; and
* forming a specific for a generic with a `T:! I` parameter where `T` is
being given a concrete value.
(Here `I` is an interface or other non-`type` facet type.)
Also do some renaming and add some comments to make things a bit more
clear.
* `FacetTypeAccess` -> `FacetAccessType` to clarify this is not access
of a facet type, but access of the type of a facet
* `.facet_id` -> `.facet_value_inst_id` to parallel the `FacetValue`
instruction
`FacetAccessWitness` will be in a future PR.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Jon Ross-Perkins
Boaz Brickner