[ConstraintGraph] Collect and print changes in current Active Scope.

Author: Amritpan Kaur

include/swift/Sema/ConstraintGraph.h

@@ -387,6 +387,7 @@ class ConstraintGraph {
   /// Print the graph.
   void print(ArrayRef<TypeVariableType *> typeVars, llvm::raw_ostream &out);
   void dump(llvm::raw_ostream &out);
+  void print(llvm::raw_ostream &out, unsigned indent = 0);
 
   // FIXME: Potentially side-effectful.
   SWIFT_DEBUG_HELPER(void dump());

lib/Sema/CSStep.h

@@ -548,6 +548,13 @@ template <typename P> class BindingStep : public SolverStep {
         auto scope = std::make_unique<Scope>(CS);
         if (attempt(*choice)) {
           ActiveChoice.emplace(std::move(scope), *choice);
+
+          if (CS.isDebugMode()) {
+            auto &log = llvm::errs();
+            auto &CG = CS.getConstraintGraph();
+            CG.print(log, CS.solverState->getCurrentIndent());
+          }
+          
           return suspend(std::make_unique<SplitterStep>(CS, Solutions));
         }
       }

lib/Sema/ConstraintGraph.cpp

@@ -1558,6 +1558,119 @@ void ConstraintGraph::dump(llvm::raw_ostream &out) {
   print(CS.getTypeVariables(), out);
 }
 
+void ConstraintGraph::print(llvm::raw_ostream &out, unsigned indent) {
+  if (Changes.empty() && (ActiveScope->getStartIdx() == Changes.size()))
+    return;
+
+  // Collect Changes for printing.
+  std::map<TypeVariableType *, TypeBase *> tvWithboundTypes;
+  std::vector<TypeVariableType *> addedTypeVars;
+  std::vector<TypeVariableType *> equivTypeVars;
+  std::vector<Constraint *> addedConstraints;
+  std::vector<Constraint *> removedConstraints;
+  for (unsigned int i = ActiveScope->getStartIdx(); i < Changes.size(); i++) {
+    auto change = Changes[i];
+    switch (change.Kind) {
+    case ChangeKind::BoundTypeVariable:
+      tvWithboundTypes.insert(std::pair<TypeVariableType *, TypeBase *>(
+          change.Binding.TypeVar, change.Binding.FixedType));
+      break;
+    case ChangeKind::AddedTypeVariable:
+      addedTypeVars.push_back(change.TypeVar);
+      break;
+    case ChangeKind::ExtendedEquivalenceClass:
+      equivTypeVars.push_back(change.EquivClass.TypeVar);
+      break;
+    case ChangeKind::AddedConstraint:
+      addedConstraints.push_back(change.TheConstraint);
+      break;
+    case ChangeKind::RemovedConstraint:
+      removedConstraints.push_back(change.TheConstraint);
+      break;
+    }
+  }
+
+  // If there are any constraints that were both added and removed in this set
+  // of Changes, remove them from both.
+  for (std::vector<Constraint *>::const_iterator itr = addedConstraints.begin();
+       itr != addedConstraints.end();) {
+    auto repeatedConstraintItr =
+        std::find(removedConstraints.begin(), removedConstraints.end(), *itr);
+    if (repeatedConstraintItr != removedConstraints.end()) {
+      removedConstraints.erase(repeatedConstraintItr);
+      itr = addedConstraints.erase(itr);
+    } else {
+      itr++;
+    }
+  }
+
+  // Print out Changes.
+  PrintOptions PO;
+  PO.PrintTypesForDebugging = true;
+  out.indent(indent);
+  out << "(Changes:\n";
+  if (!tvWithboundTypes.empty()) {
+    out.indent(indent + 2);
+    out << "(New Bound Type: \n";
+    for (const auto &tvWithType : tvWithboundTypes) {
+      out.indent(indent + 4);
+      out << "> $T" << tvWithType.first->getImpl().getID() << " := ";
+      tvWithType.second->print(out, PO);
+      out << '\n';
+    }
+    out.indent(indent + 2);
+    out << ")\n";
+  }
+  if (!addedTypeVars.empty()) {
+    out.indent(indent + 2);
+    out << "(New Type Variable: \n";
+    for (const auto &typeVar : addedTypeVars) {
+      out.indent(indent + 4);
+      out << "> $T" << typeVar->getImpl().getID();
+      out << '\n';
+    }
+    out.indent(indent + 2);
+    out << ")\n";
+  }
+  if (!equivTypeVars.empty()) {
+    out.indent(indent + 2);
+    out << "(New Equivalence Class: \n";
+    for (const auto &typeVar : equivTypeVars) {
+      out.indent(indent + 4);
+      out << "> $T" << typeVar->getImpl().getID();
+      out << '\n';
+    }
+    out.indent(indent + 2);
+    out << ")\n";
+  }
+  if (!addedConstraints.empty()) {
+    out.indent(indent + 2);
+    out << "(Added Constraint: \n";
+    for (const auto &constraint : addedConstraints) {
+      out.indent(indent + 4);
+      out << "> ";
+      constraint->print(out, &CS.getASTContext().SourceMgr);
+      out << '\n';
+    }
+    out.indent(indent + 2);
+    out << ")\n";
+  }
+  if (!removedConstraints.empty()) {
+    out.indent(indent + 2);
+    out << "(Removed Constraint: \n";
+    for (const auto &constraint : removedConstraints) {
+      out.indent(indent + 4);
+      out << "> ";
+      constraint->print(out, &CS.getASTContext().SourceMgr);
+      out << '\n';
+    }
+    out.indent(indent + 2);
+    out << ")\n";
+  }
+  out.indent(indent);
+  out << ")\n";
+}
+
 void ConstraintGraph::printConnectedComponents(
     ArrayRef<TypeVariableType *> typeVars,
     llvm::raw_ostream &out) {