Sema: SolverTrail::Change::RetiredConstraint now remembers the position

Author: slavapestov

include/swift/Sema/CSTrail.def

@@ -69,7 +69,6 @@ CLOSURE_CHANGE(RecordedPreconcurrencyClosure)
 CONSTRAINT_CHANGE(DisabledConstraint)
 CONSTRAINT_CHANGE(FavoredConstraint)
 CONSTRAINT_CHANGE(GeneratedConstraint)
-CONSTRAINT_CHANGE(RetiredConstraint)
 
 GRAPH_NODE_CHANGE(AddedConstraint)
 GRAPH_NODE_CHANGE(RemovedConstraint)
@@ -97,8 +96,9 @@ CHANGE(RecordedCaseLabelItemInfo)
 CHANGE(RecordedPotentialThrowSite)
 CHANGE(RecordedIsolatedParam)
 CHANGE(RecordedKeyPath)
+CHANGE(RetiredConstraint)
 
-LAST_CHANGE(RecordedKeyPath)
+LAST_CHANGE(RetiredConstraint)
 
 #undef LOCATOR_CHANGE
 #undef EXPR_CHANGE

include/swift/Sema/CSTrail.h

@@ -20,6 +20,8 @@
 #include "swift/AST/AnyFunctionRef.h"
 #include "swift/AST/Type.h"
 #include "swift/AST/Types.h"
+#include "swift/Sema/Constraint.h"
+#include "llvm/ADT/ilist.h"
 #include <vector>
 
 namespace llvm {
@@ -103,7 +105,6 @@ class SolverTrail {
         Type DstType;
       } Restriction;
 
-
       struct {
         GenericTypeParamType *GP;
         Type ReqTy;
@@ -119,6 +120,14 @@ class SolverTrail {
         Type OldType;
       } KeyPath;
 
+      struct {
+        /// It's former position in the inactive constraints list.
+        llvm::ilist<Constraint>::iterator Where;
+
+        /// The constraint.
+        Constraint *Constraint;
+      } Retiree;
+
       ConstraintFix *TheFix;
       ConstraintLocator *TheLocator;
       PackExpansionType *TheExpansion;
@@ -213,6 +222,10 @@ class SolverTrail {
     /// Create a change that recorded a key path expression.
     static Change RecordedKeyPath(KeyPathExpr *expr);
 
+    /// Create a change that removed a constraint from the inactive constraint list.
+    static Change RetiredConstraint(llvm::ilist<Constraint>::iterator where,
+                                    Constraint *constraint);
+
     /// Undo this change, reverting the constraint graph to the state it
     /// had prior to this change.
     ///

include/swift/Sema/ConstraintSystem.h

@@ -2538,13 +2538,6 @@ class ConstraintSystem {
     #define CS_STATISTIC(Name, Description) unsigned Name = 0;
     #include "ConstraintSolverStats.def"
 
-    /// Mark given constraint as retired along current solver path.
-    ///
-    /// \param constraint The constraint to retire temporarily.
-    void retireConstraint(Constraint *constraint) {
-      Trail.recordChange(SolverTrail::Change::RetiredConstraint(constraint));
-    }
-
     /// Add new "generated" constraint along the current solver path.
     ///
     /// \param constraint The newly generated constraint.
@@ -3924,7 +3917,10 @@ class ConstraintSystem {
   /// Remove an inactive constraint from the current constraint graph.
   void removeInactiveConstraint(Constraint *constraint) {
     CG.removeConstraint(constraint);
-    InactiveConstraints.erase(constraint);
+
+    auto where = InactiveConstraints.erase(constraint);
+    if (solverState)
+      recordChange(SolverTrail::Change::RetiredConstraint(where, constraint));
 
     if (isDebugMode() && getPhase() == ConstraintSystemPhase::Solving) {
       auto &log = llvm::errs();
@@ -3934,9 +3930,6 @@ class ConstraintSystem {
                         solverState->getCurrentIndent() + 4);
       log << ")\n";
     }
-
-    if (solverState)
-      solverState->retireConstraint(constraint);
   }
 
   /// Transfer given constraint from to active list

lib/Sema/CSTrail.cpp

@@ -296,6 +296,16 @@ SolverTrail::Change::RecordedKeyPath(KeyPathExpr *expr) {
   return result;
 }
 
+SolverTrail::Change
+SolverTrail::Change::RetiredConstraint(ConstraintList::iterator where,
+                                       Constraint *constraint) {
+  Change result;
+  result.Kind = ChangeKind::RetiredConstraint;
+  result.Retiree.Where = where;
+  result.Retiree.Constraint = constraint;
+  return result;
+}
+
 SyntacticElementTargetKey
 SolverTrail::Change::getSyntacticElementTargetKey() const {
   ASSERT(Kind == ChangeKind::RecordedTarget);
@@ -481,7 +491,8 @@ void SolverTrail::Change::undo(ConstraintSystem &cs) const {
   }
 
   case ChangeKind::RetiredConstraint:
-    cs.InactiveConstraints.push_back(TheConstraint.Constraint);
+    cs.InactiveConstraints.insert(Retiree.Where,
+                                  Retiree.Constraint);
     break;
   }
 }
@@ -674,6 +685,13 @@ void SolverTrail::Change::dump(llvm::raw_ostream &out,
     simple_display(out, KeyPath.Expr);
     out << ")\n";
     break;
+
+  case ChangeKind::RetiredConstraint:
+    out << "(RetiredConstraint ";
+    TheConstraint.Constraint->print(out, &cs.getASTContext().SourceMgr,
+                                    indent + 2);
+    out << ")\n";
+    break;
   }
 }