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Facet types support rewrite (where .A =...) constraints (#4613)

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* 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>
This commit is contained in:
josh11b
2024-12-03 22:44:39 +00:00
committed by GitHub
co-authored by Josh L Richard Smith
parent dc5edb88fb
commit 33110d096c
44 changed files with 3113 additions and 1446 deletions
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toolchain/check/context.cpp
+7 -6
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@@ -115,7 +115,8 @@ auto Context::FinishInst(SemIR::InstId inst_id, SemIR::Inst inst) -> void {
// If the instruction has a symbolic constant type, track that we need to
// substitute into it.
if (types().GetConstantId(inst.type_id()).is_symbolic()) {
if (constant_values().DependsOnGenericParameter(
types().GetConstantId(inst.type_id()))) {
dep_kind |= GenericRegionStack::DependencyKind::SymbolicType;
}
@@ -128,7 +129,7 @@ auto Context::FinishInst(SemIR::InstId inst_id, SemIR::Inst inst) -> void {
// If the constant value is symbolic, track that we need to substitute into
// it.
if (const_id.is_symbolic()) {
if (constant_values().DependsOnGenericParameter(const_id)) {
dep_kind |= GenericRegionStack::DependencyKind::SymbolicConstant;
}
}
@@ -1281,7 +1282,7 @@ auto Context::TryToDefineType(SemIR::TypeId type_id,
ResolveSpecificDefinition(*this, interface.specific_id);
}
}
// TODO: Process other requirements.
// TODO: Finish facet type resolution.
}
return true;
@@ -1304,9 +1305,9 @@ auto Context::GetTypeIdForTypeConstant(SemIR::ConstantId constant_id)
auto Context::FacetTypeFromInterface(SemIR::InterfaceId interface_id,
SemIR::SpecificId specific_id)
-> SemIR::FacetType {
SemIR::FacetTypeId facet_type_id = facet_types().Add(SemIR::FacetTypeInfo{
.impls_constraints = {{interface_id, specific_id}},
.requirement_block_id = SemIR::InstBlockId::Invalid});
SemIR::FacetTypeId facet_type_id = facet_types().Add(
SemIR::FacetTypeInfo{.impls_constraints = {{interface_id, specific_id}},
.other_requirements = false});
return {.type_id = SemIR::TypeId::TypeType, .facet_type_id = facet_type_id};
}