[ConstraintSystem] NFC: Simplify type var producer/step by referencing constraint system from bindings

Author: xedin

include/swift/Sema/ConstraintSystem.h

@@ -5857,8 +5857,7 @@ class TypeVarBindingProducer : public BindingProducer<TypeVariableBinding> {
 public:
   using Element = TypeVariableBinding;
 
-  TypeVarBindingProducer(ConstraintSystem &cs,
-                         ConstraintSystem::PotentialBindings &bindings);
+  TypeVarBindingProducer(ConstraintSystem::PotentialBindings &bindings);
 
   /// Retrieve a set of bindings available in the current state.
   ArrayRef<Binding> getCurrentBindings() const { return Bindings; }

lib/Sema/CSStep.cpp

@@ -342,7 +342,7 @@ StepResult ComponentStep::take(bool prevFailed) {
       (!disjunction || bestBindings->favoredOverDisjunction(disjunction))) {
     // Produce a type variable step.
     return suspend(
-        std::make_unique<TypeVariableStep>(CS, *bestBindings, Solutions));
+        std::make_unique<TypeVariableStep>(*bestBindings, Solutions));
   } else if (disjunction) {
     // Produce a disjunction step.
     return suspend(

lib/Sema/CSStep.h

@@ -577,9 +577,10 @@ class TypeVariableStep final : public BindingStep<TypeVarBindingProducer> {
   bool SawFirstLiteralConstraint = false;
 
 public:
-  TypeVariableStep(ConstraintSystem &cs, BindingContainer &bindings,
+  TypeVariableStep(BindingContainer &bindings,
                    SmallVectorImpl<Solution> &solutions)
-      : BindingStep(cs, {cs, bindings}, solutions), TypeVar(bindings.TypeVar) {}
+      : BindingStep(bindings.CS, {bindings}, solutions),
+        TypeVar(bindings.TypeVar) {}
 
   void setup() override;
 

lib/Sema/ConstraintSystem.cpp

@@ -5332,8 +5332,8 @@ bool ConstraintSystem::isReadOnlyKeyPathComponent(
 }
 
 TypeVarBindingProducer::TypeVarBindingProducer(
-    ConstraintSystem &cs, ConstraintSystem::PotentialBindings &bindings)
-    : BindingProducer(cs, bindings.TypeVar->getImpl().getLocator()),
+    ConstraintSystem::PotentialBindings &bindings)
+    : BindingProducer(bindings.CS, bindings.TypeVar->getImpl().getLocator()),
       TypeVar(bindings.TypeVar),
       CanBeNil(llvm::any_of(bindings.Protocols, [](Constraint *constraint) {
         auto *protocol = constraint->getProtocol();
@@ -5348,7 +5348,7 @@ TypeVarBindingProducer::TypeVarBindingProducer(
     // this problem since its rooted in the fact that constraint system
     // is under-constrained.
     if (bindings.AssociatedCodeCompletionToken) {
-      locator = cs.getConstraintLocator(bindings.AssociatedCodeCompletionToken);
+      locator = CS.getConstraintLocator(bindings.AssociatedCodeCompletionToken);
     }
 
     Bindings.push_back(Binding::forHole(TypeVar, locator));