import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

/**
 * Captures the actual type of {@code T}.
 *
 * @author Ben Yu
 */
abstract class TypeCapture<T> {

  /** Returns the captured type. */
  final Type capture() {
    Type superclass = getClass().getGenericSuperclass();
    checkArgument(superclass instanceof ParameterizedType, "%s isn't parameterized", superclass);

        new TypeResolver()
            .where(
                new TypeCapture<Iterable<Map<?, V>>>() {}.capture(),
                new TypeCapture<Iterable<Map<String, Integer>>>() {}.capture());
    assertEquals(
        new TypeCapture<K>() {}.capture(), resolver.resolveType(new TypeCapture<K>() {}.capture()));
    assertEquals(Integer.class, resolver.resolveType(new TypeCapture<V>() {}.capture()));
  }

 * non-null bound if possible, let's require a non-null bound here.
 *
 * TODO(cpovirk): Elaborate on "wouldn't behave as users might expect."
 */
public abstract class TypeParameter<T> extends TypeCapture<T> {

  final TypeVariable<?> typeVariable;

  protected TypeParameter() {
    Type type = capture();
    checkArgument(type instanceof TypeVariable, "%s should be a type variable.", type);

 * non-null bound if possible, let's require a non-null bound here.
 *
 * TODO(cpovirk): Elaborate on "wouldn't behave as users might expect."
 */
public abstract class TypeParameter<T> extends TypeCapture<T> {

  final TypeVariable<?> typeVariable;

  protected TypeParameter() {
    Type type = capture();
    checkArgument(type instanceof TypeVariable, "%s should be a type variable.", type);