// *containing* linked_ptr<> must have a constructor and destructor (even
// if they do nothing!).
//
// Bill Gibbons suggested we use something like this.
//
// Thread Safety:
//   Unlike other linked_ptr implementations, in this implementation
//   a linked_ptr object is thread-safe in the sense that:
//     - it's safe to copy linked_ptr objects concurrently,
//     - it's safe to copy *from* a linked_ptr and read its underlying

namespace tensorflow {
namespace testing {
namespace matchers {

namespace impl {

using OutEdge = std::pair<const Node*, int>;

// -----------------------------------------------------------------------------
// Implementation details.

// Properties that we match on for a particular Node.  If a particular property
// is nullopt then any value for it is allowed.
class NodeMatcherProperties {
 public: