Github user jerryshao commented on the pull request:
https://github.com/apache/spark/pull/1508#issuecomment-50702546
Hi TD, thanks for your review. I think the previous issue is that:
```scala
implicit val keyCmd: Manifest[U] =
implicitly[Manifest[AnyRef]].asInstanceOf[Manifest[U]]
```
This line of code cannot actually get the correct runtime class, the
runtime class of `keyCmd` is `Object` as
[SPARK-2103](https://issues.apache.org/jira/browse/SPARK-2103) mentioned.
The right way is like this:
```scala
implicit val keyCmd: Manifest[U] = Manifest.classTyep(keyDecodeClass)
```
Manifest can also do the same thing if we correctly feed it with class
info. But I think it would be better to change Manifest to ClassTag to keep
align with other code, so I changed to use ClassTag.
I will add this to Mima exclude.
Thanks a lot.
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