# computes a hash of a remote repo's tag state.
# Tag definitions can come from the .hgtags file stored in
# any head of any branch, and the server protocol does not
# expose the tags directly. However, the protocol does expose
# the hashes of all the branch heads, so we can use a hash of
# all those branch names and heads as a conservative snapshot
# of the entire remote repo state, and use that as the tag sum.

// metadata and synchronization.
//
// This allows us to hide concrete implementations of TensorHandle from header
// files. The interface lists the common functionality that must be provided by
// any concrete implementation. However, in cases where the true concrete class
// is needed a static_cast can be applied.
class ImmediateExecutionTensorHandle : public AbstractTensorHandle {
 public:
  // Returns number of dimensions.

#
#   Bazel will cache your builds in tensorflow/build_output/cache,
#   and will also try using public build cache results to speed up
#   your builds. This usually saves a lot of time, especially when
#   re-running tests. However, note that:
#
#    - New environments like new CUDA versions, changes to manylinux,
#      compilers, etc. can cause undefined behavior such as build failures
#      or tests passing incorrectly.

   * </ul>
   *
   * <p><b>Examples</b> (all edges are directed facing downwards)
   *
   * <p>The graph below would be valid input with start nodes of {@code a, f, c}. However, if {@code
   * b} were <i>also</i> a start node, then there would be multiple paths to reach {@code e} and
   * {@code h}.
   *
   * {@snippet :
   *    a     b      c
   *   / \   / \     |

 *   <li>hasNext()
 *   <li>hasNext();
 *   <li>remove();
 *   <li>next();
 * </ol>
 *
 * <p>This particular order of operations may be unrealistic, and testing all 3^5 of them may be
 * thought of as overkill; however, it's difficult to determine which proper subset of this massive
 * set would be sufficient to expose any possible bug. Brute force is simpler.
 *
 * <p>To use this class the concrete subclass must implement the {@link

 * interface. It does not permit null keys or values.
 *
 * <p><b>Note:</b> by default, the returned map uses equality comparisons (the {@link Object#equals
 * equals} method) to determine equality for keys or values. However, if {@link #weakKeys} was
 * specified, the map uses identity ({@code ==}) comparisons instead for keys. Likewise, if {@link
 * #weakValues} was specified, the map uses identity comparisons for values.
 *

   *
   * <p>When passed a key that is present in the map, {@code asMap().get(Object)} has the same
   * behavior as {@link #get}, returning a live collection. When passed a key that is not present,
   * however, {@code asMap().get(Object)} returns {@code null} instead of an empty collection.
   *
   * <p>Though the method signature doesn't say so explicitly, the returned map has {@link
   * SortedSet} values.
   */
  @Override

## Context

Our codebase uses `null` extensively to represent an absence of value or optionality of the argument.
We utilize nullness annotations in Java code and somewhat rely on IDE warnings to guide us.
However, the Java code we have is not fully annotated, which causes several consequences:
* IDE warnings can be misleading
* Redundant null checks may increase binary size, hurt performance, and increase cognitive load for readers

OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE....

   *
   * <p>Historically, {@code Supplier} instances in this library have implemented this method to
   * recognize certain cases where distinct {@code Supplier} instances would in fact behave
   * identically. However, as code migrates to {@code java.util.function}, that behavior will
   * disappear. It is best not to depend on it.
   */
  @Override
  boolean equals(@Nullable Object object);