Sema: Add SolverTrail::Change::InferredBindings and ::RetractedBindings

Author: slavapestov

include/swift/Sema/CSTrail.h

@@ -49,6 +49,10 @@ class SolverTrail {
     RelatedTypeVariables,
     /// Introduced a type variable's fixed type to inference.
     IntroducedToInference,
+    /// Inferred potential bindings from a constraint.
+    InferredBindings,
+    /// Retracted potential bindings from a constraint.
+    RetractedBindings,
     /// Set the fixed type or parent and flags for a type variable.
     UpdatedTypeVariable,
   };
@@ -132,6 +136,14 @@ class SolverTrail {
     /// 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);
+
+    /// Create a change that retracted bindings from a constraint.
+    static Change retractedBindings(TypeVariableType *typeVar,
+                                    Constraint *constraint);
+
     /// Create a change that updated a type variable.
     static Change updatedTypeVariable(
                TypeVariableType *typeVar,

include/swift/Sema/ConstraintGraph.h

@@ -436,6 +436,16 @@ class ConstraintGraph {
   void unrelateTypeVariables(TypeVariableType *typeVar,
                              TypeVariableType *otherTypeVar);
 
+  /// Infer bindings from the given constraint.
+  ///
+  /// Note that this it only meant to be called by SolverTrail::Change::undo().
+  void inferBindings(TypeVariableType *typeVar, Constraint *constraint);
+
+  /// Retract bindings from the given constraint.
+  ///
+  /// 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().

lib/Sema/CSBindings.cpp

@@ -1772,6 +1772,10 @@ void PotentialBindings::infer(Constraint *constraint) {
   if (!Constraints.insert(constraint).second)
     return;
 
+  // Record the change, if there are active scopes.
+  if (CS.isRecordingChanges())
+    CS.recordChange(SolverTrail::Change::inferredBindings(TypeVar, constraint));
+
   switch (constraint->getKind()) {
   case ConstraintKind::Bind:
   case ConstraintKind::Equal:
@@ -1943,6 +1947,10 @@ void PotentialBindings::retract(Constraint *constraint) {
   if (!Constraints.erase(constraint))
     return;
 
+  // Record the change, if there are active scopes.
+  if (CS.isRecordingChanges())
+    CS.recordChange(SolverTrail::Change::retractedBindings(TypeVar, constraint));
+
   Bindings.erase(
       llvm::remove_if(Bindings,
                       [&constraint](const PotentialBinding &binding) {

lib/Sema/CSTrail.cpp

@@ -99,6 +99,26 @@ SolverTrail::Change::introducedToInference(TypeVariableType *typeVar,
   return result;
 }
 
+SolverTrail::Change
+SolverTrail::Change::inferredBindings(TypeVariableType *typeVar,
+                                     Constraint *constraint) {
+  Change result;
+  result.Kind = ChangeKind::InferredBindings;
+  result.TheConstraint.TypeVar = typeVar;
+  result.TheConstraint.Constraint = constraint;
+  return result;
+}
+
+SolverTrail::Change
+SolverTrail::Change::retractedBindings(TypeVariableType *typeVar,
+                                       Constraint *constraint) {
+  Change result;
+  result.Kind = ChangeKind::RetractedBindings;
+  result.TheConstraint.TypeVar = typeVar;
+  result.TheConstraint.Constraint = constraint;
+  return result;
+}
+
 SolverTrail::Change
 SolverTrail::Change::updatedTypeVariable(
     TypeVariableType *typeVar,
@@ -142,6 +162,14 @@ void SolverTrail::Change::undo(ConstraintSystem &cs) const {
     cg.retractFromInference(Binding.TypeVar, Binding.FixedType);
     break;
 
+  case ChangeKind::InferredBindings:
+    cg.retractBindings(TheConstraint.TypeVar, TheConstraint.Constraint);
+    break;
+
+  case ChangeKind::RetractedBindings:
+    cg.inferBindings(TheConstraint.TypeVar, TheConstraint.Constraint);
+    break;
+
   case ChangeKind::UpdatedTypeVariable:
     Update.TypeVar->getImpl().setRawOptions(Update.Options);
     Update.TypeVar->getImpl().ParentOrFixed = Update.ParentOrFixed;
@@ -205,6 +233,24 @@ void SolverTrail::Change::dump(llvm::raw_ostream &out,
     out << " to inference)\n";
     break;
 
+  case ChangeKind::InferredBindings:
+    out << "(inferred bindings from ";
+    TheConstraint.Constraint->print(out, &cs.getASTContext().SourceMgr,
+                         indent + 2);
+    out << " for type variable ";
+    TheConstraint.TypeVar->print(out, PO);
+    out << ")\n";
+    break;
+
+  case ChangeKind::RetractedBindings:
+    out << "(retracted bindings from ";
+    TheConstraint.Constraint->print(out, &cs.getASTContext().SourceMgr,
+                                    indent + 2);
+    out << " for type variable ";
+    TheConstraint.TypeVar->print(out, PO);
+    out << ")\n";
+    break;
+
   case ChangeKind::UpdatedTypeVariable:
     out << "(updated type variable ";
     Update.TypeVar->print(out, PO);

lib/Sema/ConstraintGraph.cpp

@@ -609,7 +609,17 @@ void ConstraintGraph::unrelateTypeVariables(TypeVariableType *typeVar,
 }
 
 void ConstraintGraph::retractFromInference(TypeVariableType *typeVar, Type fixed) {
-  return (*this)[typeVar].retractFromInference(fixed);
+  (*this)[typeVar].retractFromInference(fixed);
+}
+
+void ConstraintGraph::inferBindings(TypeVariableType *typeVar,
+                                    Constraint *constraint) {
+  (*this)[typeVar].getCurrentBindings().infer(constraint);
+}
+
+void ConstraintGraph::retractBindings(TypeVariableType *typeVar,
+                                      Constraint *constraint) {
+  (*this)[typeVar].getCurrentBindings().retract(constraint);
 }
 
 #pragma mark Algorithms