RFR: 8263642: javac emits duplicate checkcast for first bound of intersection type in cast [v3]

[Vicente Romero]

On Wed, 2 Jun 2021 16:37:54 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> Hi all,
>> 
>> Before the phase `desugar`, the demo `(C1 & I1) o` has **one** type-cast sub-tree, `JCTypeIntersection C1&I1`, at the syntax tree. After the phase `desugar`, the `(C1 & I1) o` becomes **three** type-cast sub-trees: `JCTypeIntersection C1&I1`, `I1`, `C1`. So at phase `Gen`, `javac` generates **three** `checkcast` according to the **three** type-cast sub-trees which causes this bug.
>> 
>> This patch doesn't generate `checkcast` when the type is `JCTypeIntersection` so that the problem can be solved. And a corresponding test case is added.
>> 
>> Another way to solve this issue is that the `TransTypes` of  the `desugar` should be modified and **two** type-cast sub-trees should be generated instead of **three**. But this way may change more code than my original patch and may cause other regression.
>> 
>> Thank you for taking the time to review.
>> 
>> Best Regards.
>> --Guoxiong
>
> Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Encapsulate common code to a method

looks good

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Marked as reviewed by vromero (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3399