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Make FacetAccessType evaluate to SymbolicBindingType for type-of a BindSymbolicName (#6115)

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The SymbolicBindingType refers to the type value that will be
substituted in for the BindSymbolicName, but holds onto the EntityNameId
from the BindSymbolicName instead of (or in addition to, for now) the
instruction.

The EntityNameId will be used to look in the ScopeStack to find the
witnesses either from the BindSymbolicName instruction, or other
instructions that specify `impls` constraints against the EntityName.

This will allow us to have the `T` in `I(T)` resolve to a `.Self`
reference in the type so that we get type equality with the binding's
type: `T:! I(.Self)`.
This commit is contained in:
Dana Jansens
2025-10-06 18:56:43 +00:00
committed by GitHub
parent bd4d5805dd
commit fe020ee08b
237 changed files with 7827 additions and 7586 deletions
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toolchain/check/eval_inst.cpp
+31 -5
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@@ -200,6 +200,31 @@ auto EvalConstantInst(Context& context, SemIR::FacetAccessType inst)
return ConstantEvalResult::Existing(
context.constant_values().Get(facet_value->type_inst_id));
}
if (auto bind_name = context.insts().TryGetAs<SemIR::BindSymbolicName>(
inst.facet_value_inst_id)) {
return ConstantEvalResult::NewSamePhase(SemIR::SymbolicBindingType{
.type_id = SemIR::TypeType::TypeId,
.entity_name_id = bind_name->entity_name_id,
// TODO: This is to be removed, at which point explore if we should
// replace NewSamePhase with NewAnyPhase (to make the constant value
// concrete). This is still a symbolic type though even if the inst
// doesn't contain a symbolic constant. Previously we crashed in CHECKs
// when we had a symbolic instruction with only an EntityNameId, due to
// it not changing in a generic eval block. Maybe that has improved in
// the latest version of this instruction. If it's not symbolic, then
// SubstConstantCallbacks and other Subst callers may need to handle
// looking through concrete instructions which would be unfortunate.
.facet_value_inst_id = inst.facet_value_inst_id});
}
// The `facet_value_inst_id` is always a facet value (has type facet type).
CARBON_CHECK(context.types().Is<SemIR::FacetType>(
context.insts().Get(inst.facet_value_inst_id).type_id()));
// Other instructions (e.g. ImplWitnessAccess) of type FacetType can appear
// here, in which case the constant inst is a FacetAccessType until those
// instructions resolve to one of the above.
return ConstantEvalResult::NewSamePhase(inst);
}
@@ -207,13 +232,14 @@ auto EvalConstantInst(Context& context, SemIR::FacetValue inst)
-> ConstantEvalResult {
// A FacetValue that just wraps a BindSymbolicName without adding/removing any
// witnesses is evaluated back to the BindSymbolicName itself.
if (auto access =
context.insts().TryGetAs<SemIR::FacetAccessType>(inst.type_inst_id)) {
auto bind_id = access->facet_value_inst_id;
auto bind = context.insts().TryGetAs<SemIR::BindSymbolicName>(bind_id);
if (auto bind_as_type = context.insts().TryGetAs<SemIR::SymbolicBindingType>(
inst.type_inst_id)) {
// TODO: Look in ScopeStack with the entity_name_id to find the facet value.
auto bind_id = bind_as_type->facet_value_inst_id;
auto bind = context.insts().GetAs<SemIR::BindSymbolicName>(bind_id);
// If the FacetTypes are the same, then the FacetValue didn't add/remove
// any witnesses.
if (bind.has_value() && bind->type_id == inst.type_id) {
if (bind.type_id == inst.type_id) {
return ConstantEvalResult::Existing(
context.constant_values().Get(bind_id));
}