RFR: 8263642: javac emits duplicate checkcast for first bound of intersection type in cast [v2]

[Vicente Romero]

On Wed, 2 Jun 2021 15:26:18 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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Remove the duplicated typecast nodes in the AST instead of ignoring it
>  - Check the type of the checkcast
>  - Merge branch 'master' into JDK-8263642
>  - 8263642: javac emits duplicate checkcast for first bound of intersection type in cast

test/langtools/tools/javac/cast/intersection/DuplicatedCheckcastTest.java line 94:

> 92:                     "Expected number: 2, actual number: " + checkCastList.size());
> 93:         }
> 94:         // first checkcast

hi, there is common code in the two sections of code that check for the checkcast I suggest creating a method for the common code

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