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Sema: Address the FIXME in ConstraintGraph::mergeNodes()

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This commit is contained in:
Slava Pestov
2024-11-19 12:30:24 -05:00
parent 5690addb4e
commit 1a60685292
4 changed files with 60 additions and 49 deletions
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85
lib/Sema/ConstraintGraph.cpp
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@@ -89,8 +89,10 @@ ConstraintGraph::lookupNode(TypeVariableType *typeVar) {
// If this type variable is not the representative of its equivalence class,
// add it to its representative's set of equivalences.
auto typeVarRep = CS.getRepresentative(typeVar);
if (typeVar != typeVarRep)
mergeNodes(typeVar, typeVarRep);
if (typeVar != typeVarRep) {
mergeNodesPre(typeVar);
mergeNodes(typeVarRep, typeVar);
}
else if (auto fixed = CS.getFixedType(typeVarRep)) {
// Bind the type variable.
bindTypeVariable(typeVar, fixed);
@@ -251,32 +253,6 @@ void ConstraintGraphNode::addToEquivalenceClass(
if (EquivalenceClass.empty())
EquivalenceClass.push_back(getTypeVariable());
EquivalenceClass.append(typeVars.begin(), typeVars.end());
{
for (auto *newMember : typeVars) {
auto &node = CG[newMember];
for (auto *constraint : node.getConstraints()) {
introduceToInference(constraint);
if (!isUsefulForReferencedVars(constraint))
continue;
notifyReferencedVars([&](ConstraintGraphNode &referencedVar) {
referencedVar.introduceToInference(constraint);
});
}
// FIXME: Perhaps this also needs to be split up into two stages,
// where the first stage runs before we merge the equivalence
// classes
node.notifyReferencingVars(
[&](ConstraintGraphNode &node, Constraint *constraint) {
node.retractFromInference(constraint);
node.introduceToInference(constraint);
});
}
}
}
void ConstraintGraphNode::truncateEquivalenceClass(unsigned prevSize) {
@@ -525,31 +501,60 @@ void ConstraintGraph::removeConstraint(TypeVariableType *typeVar,
OrphanedConstraints.pop_back();
}
void ConstraintGraph::mergeNodesPre(TypeVariableType *typeVar2) {
// Merge equivalence class from the non-representative type variable.
auto &nonRepNode = (*this)[typeVar2];
for (auto *newMember : nonRepNode.getEquivalenceClassUnsafe()) {
auto &node = (*this)[newMember];
node.notifyReferencingVars(
[&](ConstraintGraphNode &node, Constraint *constraint) {
node.retractFromInference(constraint);
});
}
}
void ConstraintGraph::mergeNodes(TypeVariableType *typeVar1,
TypeVariableType *typeVar2) {
assert(CS.getRepresentative(typeVar1) == CS.getRepresentative(typeVar2) &&
"type representatives don't match");
// Retrieve the node for the representative that we're merging into.
auto typeVarRep = CS.getRepresentative(typeVar1);
auto &repNode = (*this)[typeVarRep];
ASSERT(CS.getRepresentative(typeVar1) == typeVar1);
// Retrieve the node for the non-representative.
assert((typeVar1 == typeVarRep || typeVar2 == typeVarRep) &&
"neither type variable is the new representative?");
auto typeVarNonRep = typeVar1 == typeVarRep? typeVar2 : typeVar1;
auto &repNode = (*this)[typeVar1];
// Record the change, if there are active scopes.
if (CS.isRecordingChanges()) {
CS.recordChange(
SolverTrail::Change::ExtendedEquivalenceClass(
typeVarRep,
typeVar1,
repNode.getEquivalenceClass().size()));
}
// Merge equivalence class from the non-representative type variable.
auto &nonRepNode = (*this)[typeVarNonRep];
repNode.addToEquivalenceClass(nonRepNode.getEquivalenceClassUnsafe());
auto &nonRepNode = (*this)[typeVar2];
auto typeVars = nonRepNode.getEquivalenceClassUnsafe();
repNode.addToEquivalenceClass(typeVars);
for (auto *newMember : typeVars) {
auto &node = (*this)[newMember];
for (auto *constraint : node.getConstraints()) {
repNode.introduceToInference(constraint);
if (!isUsefulForReferencedVars(constraint))
continue;
repNode.notifyReferencedVars([&](ConstraintGraphNode &referencedVar) {
referencedVar.introduceToInference(constraint);
});
}
node.notifyReferencingVars(
[&](ConstraintGraphNode &node, Constraint *constraint) {
node.introduceToInference(constraint);
});
}
}
void ConstraintGraph::bindTypeVariable(TypeVariableType *typeVar, Type fixed) {