[jira] Updated: (PIG-1288) EvalFunc returnType is wrong for generic subclasses

["Daniel Dai (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PIG-1288?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Daniel Dai updated PIG-1288:
----------------------------

    Status: Open  (was: Patch Available)

> EvalFunc returnType is wrong for generic subclasses
> ---------------------------------------------------
>
>                 Key: PIG-1288
>                 URL: https://issues.apache.org/jira/browse/PIG-1288
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.7.0
>            Reporter: Daniel Dai
>            Assignee: Daniel Dai
>             Fix For: 0.8.0
>
>         Attachments: PIG-1288-1.patch, PIG-1288-2.patch, PIG-1288-3.patch, PIG-1288-4.patch
>
>
> From Garrett Buster Kaminaga:
> The EvalFunc constructor has code to determine the return type of the function.
> This walks up the object hierarchy until it encounters EvalFunc, then calls getActualTypeArguments and extracts type
> param 0.
> However, if the user class is itself a generic extension of EvalFunc, then the returned object is not the correct type,
> but a TypeVariable.
> Example:
>   class MyAbstractEvalFunc<T> extends EvalFunc<T> ...
>   class MyEvalFunc extends MyAbstractEvalFunc<String> ...
> when MyEvalFunc() is called, inside EvalFunc constructor the return type is set to a TypeVariable rather than
> String.class.
> The workaround we've implemented is for the MyAbstractEvalFunc<T> to determine *its* type parameters using code
> similar to that in the EvalFunc constructor, and then reset protected data member returnType manually in the
> MyAbstractEvalFunc constructor.  (though this has the same drawback of not working if someone then extends
> MyAbstractEvalFunc)

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