Revert "Sema: Remove one-way constraint handling from computeConnectedComponents()"

This reverts commit dd3e49c.

Author: slavapestov

include/swift/Sema/Constraint.h

@@ -820,6 +820,11 @@ class Constraint final : public llvm::ilist_node<Constraint>,
   /// from the rest of the constraint system.
   bool isIsolated() const { return IsIsolated; }
 
+  /// Whether this is a one-way constraint.
+  bool isOneWayConstraint() const {
+    return false;
+  }
+
   /// Retrieve the overload choice for an overload-binding constraint.
   OverloadChoice getOverloadChoice() const {
     assert(Kind == ConstraintKind::BindOverload);

lib/Sema/CSStep.cpp

@@ -337,6 +337,16 @@ StepResult ComponentStep::take(bool prevFailed) {
       CS.replaySolution(*partial);
     }
 
+    // Activate all of the one-way constraints.
+    SmallVector<Constraint *, 4> oneWayConstraints;
+    for (auto &constraint : CS.InactiveConstraints) {
+      if (constraint.isOneWayConstraint())
+        oneWayConstraints.push_back(&constraint);
+    }
+    for (auto constraint : oneWayConstraints) {
+      CS.activateConstraint(constraint);
+    }
+
     // Simplify again.
     if (CS.failedConstraint || CS.simplify())
       return done(/*isSuccess=*/false);