Revert "remove unused ctor"

This reverts commit 565009db68.

arangod/VocBase/TraverserOptions.cpp

@@ -347,6 +347,33 @@ arangodb::traverser::TraverserOptions::TraverserOptions(
       useBreadthFirst);
 }
 
+arangodb::traverser::TraverserOptions::TraverserOptions(
+    TraverserOptions const& other)
+    : _trx(other._trx),
+      _baseVertexExpression(nullptr),
+      _tmpVar(nullptr),
+      _ctx(new aql::FixedVarExpressionContext()),
+      _isCoordinator(arangodb::ServerState::instance()->isCoordinator()),
+      minDepth(other.minDepth),
+      maxDepth(other.maxDepth),
+      useBreadthFirst(other.useBreadthFirst),
+      uniqueVertices(other.uniqueVertices),
+      uniqueEdges(other.uniqueEdges) {
+  TRI_ASSERT(other._baseLookupInfos.empty());
+  TRI_ASSERT(other._depthLookupInfo.empty());
+  TRI_ASSERT(other._vertexExpressions.empty());
+  TRI_ASSERT(other._tmpVar == nullptr);
+  TRI_ASSERT(other._baseVertexExpression == nullptr);
+
+  // Check for illegal option combination:
+  TRI_ASSERT(uniqueEdges !=
+             arangodb::traverser::TraverserOptions::UniquenessLevel::GLOBAL);
+  TRI_ASSERT(
+      uniqueVertices !=
+          arangodb::traverser::TraverserOptions::UniquenessLevel::GLOBAL ||
+      useBreadthFirst);
+}
+
 arangodb::traverser::TraverserOptions::~TraverserOptions() {
   for (auto& pair : _vertexExpressions) {
     delete pair.second;

arangod/VocBase/TraverserOptions.h

@@ -135,6 +135,10 @@ struct TraverserOptions {
   TraverserOptions(arangodb::aql::Query*, arangodb::velocypack::Slice,
                    arangodb::velocypack::Slice);
 
+  /// @brief This copy constructor is only working during planning phase.
+  ///        After planning this node should not be copied anywhere.
+  TraverserOptions(TraverserOptions const&);
+
   virtual ~TraverserOptions();
 
   /// @brief Build a velocypack for cloning in the plan.