#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.
/*
 * Copyright (C) 2014 The Guava Authors
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 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
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 * http://www.apache.org/licenses/LICENSE-2.0
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package com.google.common.eventbus;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.MoreObjects;
import com.google.common.base.Objects;
import com.google.common.base.Throwables;