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AST: Re-implement ProtocolConformanceRef::getAssociatedConformance() as a primitive

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This commit is contained in:
Slava Pestov
2024-09-18 15:46:45 -04:00
parent a911693c8c
commit 9afff03a1a
1 changed files with 40 additions and 10 deletions
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50
lib/AST/ProtocolConformanceRef.cpp
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@@ -20,6 +20,7 @@
#include "swift/AST/Availability.h"
#include "swift/AST/ConformanceLookup.h"
#include "swift/AST/Decl.h"
#include "swift/AST/GenericEnvironment.h"
#include "swift/AST/InFlightSubstitution.h"
#include "swift/AST/Module.h"
#include "swift/AST/PackConformance.h"
@@ -250,7 +251,8 @@ ProtocolConformanceRef
ProtocolConformanceRef::getAssociatedConformance(Type conformingType,
Type assocType,
ProtocolDecl *protocol) const {
// If this is a pack conformance, project the associated conformances.
// If this is a pack conformance, project the associated conformances from
// each pack element.
if (isPack()) {
auto *pack = getPack();
assert(conformingType->isEqual(pack->getType()));
@@ -258,21 +260,49 @@ ProtocolConformanceRef::getAssociatedConformance(Type conformingType,
pack->getAssociatedConformance(assocType, protocol));
}
// If this is a concrete conformance, look up the associated conformance.
// If this is a concrete conformance, project the associated conformance.
if (isConcrete()) {
auto conformance = getConcrete();
assert(conformance->getType()->isEqual(conformingType));
return conformance->getAssociatedConformance(assocType, protocol);
}
// Otherwise, apply the substitution {self -> conformingType}
// to the abstract conformance requirement laid upon the dependent type
// by the protocol.
auto subMap =
SubstitutionMap::getProtocolSubstitutions(getRequirement(),
conformingType, *this);
auto abstractConf = ProtocolConformanceRef(protocol);
return abstractConf.subst(assocType, subMap);
// An associated conformance of an archetype might be known to be
// a concrete conformance, if the subject type is fixed to a concrete
// type in the archetype's generic signature. We don't actually have
// any way to recover the conformance in this case, except via global
// conformance lookup.
//
// However, if we move to a first-class representation of abstract
// conformances where they store their subject types, we can also
// cache the lookups inside the abstract conformance instance too.
if (auto archetypeType = conformingType->getAs<ArchetypeType>()) {
conformingType = archetypeType->getInterfaceType();
auto *genericEnv = archetypeType->getGenericEnvironment();
auto subjectType = assocType.transformRec(
[&](TypeBase *t) -> std::optional<Type> {
if (isa<GenericTypeParamType>(t))
return conformingType;
return std::nullopt;
});
return lookupConformance(
genericEnv->mapTypeIntoContext(subjectType),
protocol);
}
// Associated conformances of type parameters and type variables
// are always abstract, because we don't know the output generic
// signature of the substitution (or in the case of type variables,
// we have no visibility into constraints). See the parallel hack
// to handle this in SubstitutionMap::lookupConformance().
CONDITIONAL_ASSERT(conformingType->isTypeParameter() ||
conformingType->isTypeVariableOrMember() ||
conformingType->is<UnresolvedType>() ||
conformingType->is<PlaceholderType>());
return ProtocolConformanceRef(protocol);
}
/// Check of all types used by the conformance are canonical.