Sema: Remove SolverTrail::Change::introducedToInference()

Author: slavapestov

include/swift/Sema/CSTrail.h

@@ -47,8 +47,6 @@ class SolverTrail {
     ExtendedEquivalenceClass,
     /// Added a new edge in the constraint graph.
     RelatedTypeVariables,
-    /// Introduced a type variable's fixed type to inference.
-    IntroducedToInference,
     /// Inferred potential bindings from a constraint.
     InferredBindings,
     /// Retracted potential bindings from a constraint.
@@ -93,14 +91,6 @@ class SolverTrail {
         TypeVariableType *OtherTypeVar;
       } Relation;
 
-      struct {
-        /// The type variable being bound to a fixed type.
-        TypeVariableType *TypeVar;
-
-        /// The fixed type to which the type variable was bound.
-        TypeBase *FixedType;
-      } Binding;
-
       struct {
         /// The type variable being updated.
         TypeVariableType *TypeVar;
@@ -133,9 +123,6 @@ class SolverTrail {
     static Change relatedTypeVariables(TypeVariableType *typeVar,
                                        TypeVariableType *otherTypeVar);
 
-    /// Create a change that introduced a type variable to inference.
-    static Change introducedToInference(TypeVariableType *typeVar, Type fixed);
-
     /// Create a change that inferred bindings from a constraint.
     static Change inferredBindings(TypeVariableType *typeVar,
                                    Constraint *constraint);

include/swift/Sema/ConstraintGraph.h

@@ -153,9 +153,6 @@ class ConstraintGraphNode {
   /// type variable has been bound to a valid type and solver can make progress.
   void introduceToInference(Type fixedType);
 
-  /// Opposite of \c introduceToInference(Type)
-  void retractFromInference(Type fixedType);
-
   /// Drop all previously collected bindings and re-infer based on the
   /// current set constraints associated with this equivalence class.
   void resetBindingSet();
@@ -446,11 +443,6 @@ class ConstraintGraph {
   /// Note that this it only meant to be called by SolverTrail::Change::undo().
   void retractBindings(TypeVariableType *typeVar, Constraint *constraint);
 
-  /// Retract the given type variable from inference.
-  ///
-  /// Note that this it only meant to be called by SolverTrail::Change::undo().
-  void retractFromInference(TypeVariableType *typeVar, Type fixedType);
-
   /// Perform edge contraction on the constraint graph, merging equivalence
   /// classes until a fixed point is reached.
   bool contractEdges();

lib/Sema/CSTrail.cpp

@@ -89,16 +89,6 @@ SolverTrail::Change::relatedTypeVariables(TypeVariableType *typeVar,
   return result;
 }
 
-SolverTrail::Change
-SolverTrail::Change::introducedToInference(TypeVariableType *typeVar,
-                                           Type fixed) {
-  Change result;
-  result.Kind = ChangeKind::IntroducedToInference;
-  result.Binding.TypeVar = typeVar;
-  result.Binding.FixedType = fixed.getPointer();
-  return result;
-}
-
 SolverTrail::Change
 SolverTrail::Change::inferredBindings(TypeVariableType *typeVar,
                                      Constraint *constraint) {
@@ -158,10 +148,6 @@ void SolverTrail::Change::undo(ConstraintSystem &cs) const {
     cg.unrelateTypeVariables(Relation.TypeVar, Relation.OtherTypeVar);
     break;
 
-  case ChangeKind::IntroducedToInference:
-    cg.retractFromInference(Binding.TypeVar, Binding.FixedType);
-    break;
-
   case ChangeKind::InferredBindings:
     cg.retractBindings(TheConstraint.TypeVar, TheConstraint.Constraint);
     break;
@@ -225,14 +211,6 @@ void SolverTrail::Change::dump(llvm::raw_ostream &out,
     out << ")\n";
     break;
 
-  case ChangeKind::IntroducedToInference:
-    out << "(introduced type variable ";
-    Binding.TypeVar->print(out, PO);
-    out << " with fixed type ";
-    Binding.FixedType->print(out, PO);
-    out << " to inference)\n";
-    break;
-
   case ChangeKind::InferredBindings:
     out << "(inferred bindings from ";
     TheConstraint.Constraint->print(out, &cs.getASTContext().SourceMgr,

lib/Sema/ConstraintGraph.cpp

@@ -92,11 +92,6 @@ ConstraintGraph::lookupNode(TypeVariableType *typeVar) {
   if (typeVar != typeVarRep)
     mergeNodes(typeVar, typeVarRep);
   else if (auto fixed = CS.getFixedType(typeVarRep)) {
-    // FIXME: This is totally the wrong place to do it. We should do this in
-    // introduceToInference().
-    if (CS.isRecordingChanges())
-      CS.recordChange(SolverTrail::Change::introducedToInference(typeVar, fixed));
-
     // Bind the type variable.
     bindTypeVariable(typeVar, fixed);
   }
@@ -381,24 +376,6 @@ void ConstraintGraphNode::introduceToInference(Type fixedType) {
   }
 }
 
-void ConstraintGraphNode::retractFromInference(Type fixedType) {
-  // Notify referencing variables (just like in bound case) that this
-  // type variable has been modified.
-  notifyReferencingVars();
-
-  SmallPtrSet<TypeVariableType *, 4> referencedVars;
-  fixedType->getTypeVariables(referencedVars);
-
-  // TODO: This might be an overkill but it's (currently)
-  // the simplest way to reliably ensure that all of the
-  // no longer related constraints have been retracted.
-  for (auto *referencedVar : referencedVars) {
-    auto &node = CG[referencedVar];
-    if (node.forRepresentativeVar())
-      node.resetBindingSet();
-  }
-}
-
 void ConstraintGraphNode::resetBindingSet() {
   assert(forRepresentativeVar());
 
@@ -585,10 +562,6 @@ void ConstraintGraph::unrelateTypeVariables(TypeVariableType *typeVar,
   node.removeReference(otherTypeVar);
 }
 
-void ConstraintGraph::retractFromInference(TypeVariableType *typeVar, Type fixed) {
-  (*this)[typeVar].retractFromInference(fixed);
-}
-
 void ConstraintGraph::inferBindings(TypeVariableType *typeVar,
                                     Constraint *constraint) {
   (*this)[typeVar].getCurrentBindings().infer(constraint);

lib/Sema/ConstraintSystem.cpp

@@ -239,11 +239,6 @@ void ConstraintSystem::assignFixedType(TypeVariableType *typeVar, Type type,
     }
   }
 
-  // FIXME: This is totally the wrong place to do it. We should do this in
-  // introduceToInference().
-  if (isRecordingChanges())
-    recordChange(SolverTrail::Change::introducedToInference(typeVar, type));
-
   // Notify the constraint graph.
   CG.bindTypeVariable(typeVar, type);