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[CSBindings] Transform literal requirements into bindings when type variable is attempted

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This commit is contained in:
Pavel Yaskevich
2020-12-24 16:35:46 -08:00
parent 731810e184
commit e676e05f13
4 changed files with 115 additions and 85 deletions
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43
lib/Sema/ConstraintSystem.cpp
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@@ -195,8 +195,9 @@ void ConstraintSystem::assignFixedType(TypeVariableType *typeVar, Type type,
if (auto defaultType = TypeChecker::getDefaultType(literalProtocol, DC)) {
// Check whether the nominal types match. This makes sure that we
// properly handle Array vs. Array<T>.
if (defaultType->getAnyNominal() != type->getAnyNominal())
if (defaultType->getAnyNominal() != type->getAnyNominal()) {
increaseScore(SK_NonDefaultLiteral);
}
}
}
}
@@ -5349,18 +5350,48 @@ TypeVarBindingProducer::TypeVarBindingProducer(
// A binding to `Any` which should always be considered as a last resort.
Optional<Binding> Any;
for (const auto &binding : bindings.Bindings) {
auto type = binding.BindingType;
auto addBinding = [&](const Binding &binding) {
// Adjust optionality of existing bindings based on presence of
// `ExpressibleByNilLiteral` requirement.
if (requiresOptionalAdjustment(binding)) {
Bindings.push_back(binding.withType(OptionalType::get(type)));
} else if (type->isAny()) {
Bindings.push_back(
binding.withType(OptionalType::get(binding.BindingType)));
} else if (binding.BindingType->isAny()) {
Any.emplace(binding);
} else {
Bindings.push_back(binding);
}
};
for (const auto &binding : bindings.Bindings) {
addBinding(binding);
}
// Infer defaults based on "uncovered" literal protocol requirements.
for (const auto &literal : bindings.Literals) {
Constraint *constraint = nullptr;
bool isDirectRequirement = false;
Constraint *coveredBy = nullptr;
std::tie(constraint, isDirectRequirement, coveredBy) = literal.second;
// Can't be defaulted because it's already covered by an
// existing direct or transitive binding which is always
// better.
if (coveredBy)
continue;
auto defaultType = TypeChecker::getDefaultType(literal.first, CS.DC);
if (!defaultType)
continue;
// We need to figure out whether this is a direct conformance
// requirement or inferred transitive one to identify binding
// kind correctly.
addBinding(
{defaultType,
isDirectRequirement ? BindingKind::Subtypes : BindingKind::Supertypes,
constraint});
}
// Let's always consider `Any` to be a last resort binding because