Sema: ConstraintGraph::retractFromInference() doesn't need the new fixed type

Author: slavapestov

include/swift/Sema/ConstraintGraph.h

@@ -148,7 +148,7 @@ class ConstraintGraphNode {
 
   /// Perform graph updates that must be undone after we bind a fixed type
   /// to a type variable.
-  void retractFromInference(Type fixedType);
+  void retractFromInference();
 
   /// Perform graph updates that must be undone before we bind a fixed type
   /// to a type variable.
@@ -294,7 +294,7 @@ class ConstraintGraph {
 
   /// Perform graph updates that must be undone after we bind a fixed type
   /// to a type variable.
-  void retractFromInference(TypeVariableType *typeVar, Type fixedType);
+  void retractFromInference(TypeVariableType *typeVar);
 
   /// Perform graph updates that must be undone before we bind a fixed type
   /// to a type variable.

lib/Sema/ConstraintGraph.cpp

@@ -322,10 +322,16 @@ void ConstraintGraphNode::updateFixedType(
   }
 }
 
-void ConstraintGraphNode::retractFromInference(Type fixedType) {
+void ConstraintGraphNode::retractFromInference() {
   auto &cs = CG.getConstraintSystem();
-  return updateFixedType(
-      fixedType,
+
+  // Notify all of the type variables that reference this one.
+  //
+  // Since this type variable is going to be replaced with a fixed type
+  // all of the concrete types that reference it are going to change,
+  // which means that all of the not-yet-attempted bindings should
+  // change as well.
+  return notifyReferencingVars(
       [&cs](ConstraintGraphNode &node, Constraint *constraint) {
         node.getPotentialBindings().retract(cs, node.getTypeVariable(), constraint);
       });
@@ -523,8 +529,8 @@ void ConstraintGraph::bindTypeVariable(TypeVariableType *typeVar, Type fixed) {
   }
 }
 
-void ConstraintGraph::retractFromInference(TypeVariableType *typeVar, Type fixed) {
-  (*this)[typeVar].retractFromInference(fixed);
+void ConstraintGraph::retractFromInference(TypeVariableType *typeVar) {
+  (*this)[typeVar].retractFromInference();
 }
 
 void ConstraintGraph::introduceToInference(TypeVariableType *typeVar, Type fixed) {

lib/Sema/ConstraintSystem.cpp

@@ -217,7 +217,7 @@ void ConstraintSystem::assignFixedType(TypeVariableType *typeVar, Type type,
   assert(!type->hasError() &&
          "Should not be assigning a type involving ErrorType!");
 
-  CG.retractFromInference(typeVar, type);
+  CG.retractFromInference(typeVar);
   typeVar->getImpl().assignFixedType(type, getTrail());
 
   if (!updateState)