Merge pull request #17991 from rudkx/remove-binding-optimization-2
[ConstraintSystem] Remove an attempted optimization that we've not
diff --git a/lib/Sema/CSSolver.cpp b/lib/Sema/CSSolver.cpp
index 5fe8e74..4f0a191 100644
--- a/lib/Sema/CSSolver.cpp
+++ b/lib/Sema/CSSolver.cpp
@@ -1856,91 +1856,10 @@
return false;
}
-// Attempt to find a disjunction of bind constraints where all options
-// in the disjunction are binding the same type variable.
-//
-// Prefer disjunctions where the bound type variable is also the
-// right-hand side of a conversion constraint, since having a concrete
-// type that we're converting to can make it possible to split the
-// constraint system into multiple ones.
-static Constraint *selectBestBindingDisjunction(
- ConstraintSystem &cs, SmallVectorImpl<Constraint *> &disjunctions) {
-
- if (disjunctions.empty())
- return nullptr;
-
- // Collect any disjunctions that simply attempt bindings for a
- // type variable.
- SmallVector<Constraint *, 8> bindingDisjunctions;
- for (auto *disjunction : disjunctions) {
- llvm::Optional<TypeVariableType *> commonTypeVariable;
- if (llvm::all_of(
- disjunction->getNestedConstraints(),
- [&](Constraint *bindingConstraint) {
- if (bindingConstraint->getKind() != ConstraintKind::Bind)
- return false;
-
- auto *tv =
- bindingConstraint->getFirstType()->getAs<TypeVariableType>();
- // Only do this for simple type variable bindings, not for
- // bindings like: ($T1) -> $T2 bind String -> Int
- if (!tv)
- return false;
-
- if (!commonTypeVariable.hasValue())
- commonTypeVariable = tv;
-
- if (commonTypeVariable.getValue() != tv)
- return false;
-
- return true;
- })) {
- bindingDisjunctions.push_back(disjunction);
- }
- }
-
- for (auto *disjunction : bindingDisjunctions) {
- auto nested = disjunction->getNestedConstraints();
- assert(!nested.empty());
- auto *tv = cs.simplifyType(nested[0]->getFirstType())
- ->getRValueType()
- ->getAs<TypeVariableType>();
- assert(tv);
-
- SmallVector<Constraint *, 8> constraints;
- cs.getConstraintGraph().gatherConstraints(
- tv, constraints, ConstraintGraph::GatheringKind::EquivalenceClass);
-
- for (auto *constraint : constraints) {
- if (constraint->getKind() != ConstraintKind::Conversion)
- continue;
-
- auto toType =
- cs.simplifyType(constraint->getSecondType())->getRValueType();
- auto *toTV = toType->getAs<TypeVariableType>();
- if (tv != toTV)
- continue;
-
- return disjunction;
- }
- }
-
- // If we had any binding disjunctions, return the first of
- // those. These ensure that we attempt to bind types earlier than
- // trying the elements of other disjunctions, which can often mean
- // we fail faster.
- if (!bindingDisjunctions.empty())
- return bindingDisjunctions[0];
-
- return nullptr;
-}
-
Constraint *ConstraintSystem::selectDisjunction() {
SmallVector<Constraint *, 4> disjunctions;
collectDisjunctions(disjunctions);
- if (auto *disjunction = selectBestBindingDisjunction(*this, disjunctions))
- return disjunction;
// Pick the disjunction with the lowest disjunction number in order
// to solve them in the order they were created (which should be
