Sema: Record fixes in the trail

Author: slavapestov

include/swift/Sema/CSTrail.h

@@ -55,6 +55,8 @@ class SolverTrail {
     UpdatedTypeVariable,
     /// Recorded a conversion restriction kind.
     AddedConversionRestriction,
+    /// Recorded a fix.
+    AddedFix,
   };
 
   /// A change made to the constraint system.
@@ -111,6 +113,8 @@ class SolverTrail {
         /// The destination type.
         Type DstType;
       } Restriction;
+
+      ConstraintFix *Fix;
     };
 
     Change() : Kind(ChangeKind::AddedTypeVariable), TypeVar(nullptr) { }
@@ -150,6 +154,9 @@ class SolverTrail {
     /// Create a change that recorded a restriction.
     static Change addedConversionRestriction(Type srcType, Type dstType);
 
+    /// Create a change that recorded a fix.
+    static Change addedFix(ConstraintFix *fix);
+
     /// Undo this change, reverting the constraint graph to the state it
     /// had prior to this change.
     ///

include/swift/Sema/ConstraintSystem.h

@@ -2859,6 +2859,8 @@ class ConstraintSystem {
     unsigned numTrailChanges;
 
     /// The length of \c Fixes.
+    ///
+    /// FIXME: Remove this.
     unsigned numFixes;
 
     /// The length of \c FixedRequirements.
@@ -4222,6 +4224,12 @@ class ConstraintSystem {
   /// Called to undo the above change.
   void removeConversionRestriction(Type srcType, Type dstType);
 
+  /// Update Fixes and record a change in the trail.
+  void addFix(ConstraintFix *fix);
+
+  /// Called to undo the above change.
+  void removeFix(ConstraintFix *fix);
+
   /// Determine whether the given type is a dictionary and, if so, provide the
   /// key and value types for the dictionary.
   static std::optional<std::pair<Type, Type>> isDictionaryType(Type type);

lib/Sema/CSSimplify.cpp

@@ -14855,7 +14855,7 @@ bool ConstraintSystem::recordFix(ConstraintFix *fix, unsigned impact) {
     return true;
 
   if (isAugmentingFix(fix)) {
-    Fixes.insert(fix);
+    addFix(fix);
     return false;
   }
 
@@ -14887,7 +14887,7 @@ bool ConstraintSystem::recordFix(ConstraintFix *fix, unsigned impact) {
   }
 
   if (!found)
-    Fixes.insert(fix);
+    addFix(fix);
 
   return false;
 }

lib/Sema/CSSolver.cpp

@@ -419,7 +419,8 @@ void ConstraintSystem::applySolution(const Solution &solution) {
   }
 
   // Register any fixes produced along this path.
-  Fixes.insert(solution.Fixes.begin(), solution.Fixes.end());
+  for (auto *fix : solution.Fixes)
+    addFix(fix);
 }
 bool ConstraintSystem::simplify() {
   // While we have a constraint in the worklist, process it.
@@ -719,9 +720,6 @@ ConstraintSystem::SolverScope::~SolverScope() {
   // constraints introduced by the current scope.
   cs.solverState->rollback(this);
 
-  // Remove any fixes.
-  truncate(cs.Fixes, numFixes);
-
   // Remove any disjunction choices.
   truncate(cs.DisjunctionChoices, numDisjunctionChoices);
 

lib/Sema/CSTrail.cpp

@@ -131,6 +131,14 @@ SolverTrail::Change::addedConversionRestriction(Type srcType, Type dstType) {
   return result;
 }
 
+SolverTrail::Change
+SolverTrail::Change::addedFix(ConstraintFix *fix) {
+  Change result;
+  result.Kind = ChangeKind::AddedFix;
+  result.Fix = fix;
+  return result;
+}
+
 void SolverTrail::Change::undo(ConstraintSystem &cs) const {
   auto &cg = cs.getConstraintGraph();
 
@@ -174,6 +182,10 @@ void SolverTrail::Change::undo(ConstraintSystem &cs) const {
     cs.removeConversionRestriction(Restriction.SrcType,
                                    Restriction.DstType);
     break;
+
+  case ChangeKind::AddedFix:
+    cs.removeFix(Fix);
+    break;
   }
 }
 
@@ -269,6 +281,12 @@ void SolverTrail::Change::dump(llvm::raw_ostream &out,
     Restriction.DstType->print(out, PO);
     out << ")\n";
     break;
+
+  case ChangeKind::AddedFix:
+    out << "(added a fix ";
+    Fix->print(out);
+    out << ")\n";
+    break;
   }
 }
 

lib/Sema/ConstraintSystem.cpp

@@ -279,6 +279,20 @@ void ConstraintSystem::removeConversionRestriction(
   ASSERT(erased);
 }
 
+void ConstraintSystem::addFix(ConstraintFix *fix) {
+  bool inserted = Fixes.insert(fix);
+  if (!inserted)
+    return;
+
+  if (isRecordingChanges())
+    recordChange(SolverTrail::Change::addedFix(fix));
+}
+
+void ConstraintSystem::removeFix(ConstraintFix *fix) {
+  ASSERT(Fixes.back() == fix);
+  Fixes.pop_back();
+}
+
 /// Retrieve a dynamic result signature for the given declaration.
 static std::tuple<char, ObjCSelector, CanType>
 getDynamicResultSignature(ValueDecl *decl) {