#3989 raises the issue that `@Subscribe` methods with primitive parameter types can be registered but they will never be called because the `post()` method takes `Object` and so autoboxes primitives.

`EventBus` should throw an exception preventing registering any `@Subscribe` methods with primitive parameters and document the restriction.
*
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.common.eventbus;
import com.google.common.annotations.Beta;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
 * Marks a method as an event subscriber.
 *
 * <p>The type of event will be indicated by the method's first (and only) parameter. If this
 * annotation is applied to methods with zero parameters, or more than one parameter, the object
 * containing the method will not be able to register for event delivery from the {@link EventBus}.
 *
 * <p>Unless also annotated with @{@link AllowConcurrentEvents}, event subscriber methods will be
 * invoked serially by each event bus that they are registered with.
 *
 * @author Cliff Biffle
 * @since 10.0
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@Beta
public @interface Subscribe {}