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8263642: javac emits duplicate checkcast for first bound of intersection type in cast #3399

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@lgxbslgx lgxbslgx commented Apr 8, 2021

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


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  • JDK-8263642: javac emits duplicate checkcast for first bound of intersection type in cast

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👋 Welcome back lgxbslgx! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

@openjdk openjdk bot added the rfr Pull request is ready for review label Apr 8, 2021
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@lgxbslgx The following label will be automatically applied to this pull request:

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Webrevs

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@lgxbslgx This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply add a new comment to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

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Ping. Could I ask your help to review this patch? Thanks a lot.

Code_attribute code_attribute = (Code_attribute) method.attributes.get(Attribute.Code);
for (Instruction instruction : code_attribute.getInstructions()) {
if ("checkcast".equals(instruction.getMnemonic())) {
checkcastNumber++;
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I think that the test should check not only for the number of checkcast but also for the type the checkcast is checking against.

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Added.

@@ -2221,7 +2221,8 @@ public void visitTypeCast(JCTypeCast tree) {
// the conversion.
if (!tree.clazz.type.isPrimitive() &&
!types.isSameType(tree.expr.type, tree.clazz.type) &&
types.asSuper(tree.expr.type, tree.clazz.type.tsym) == null) {
types.asSuper(tree.expr.type, tree.clazz.type.tsym) == null &&
tree.clazz.getTag() != TYPEINTERSECTION) {
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I think that if the right form of the AST is one that have only two type casts, then that's what the fix should be doing

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I revised the patch to adjust the AST. Now it has only two type casts instead of three.

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lgxbslgx commented Jun 2, 2021

@vicente-romero-oracle Thanks for your review. I updated the patch just now.

throw new AssertionError("The number of the instruction 'checkcast' is not right. " +
"Expected number: 2, actual number: " + checkCastList.size());
}
// first checkcast
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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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Fixed.

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looks good

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openjdk bot commented Jun 2, 2021

@lgxbslgx This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8263642: javac emits duplicate checkcast for first bound of intersection type in cast

Reviewed-by: vromero

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 4 new commits pushed to the master branch:

  • e1462e7: 8267176: StandardDoclet should provide access to Reporter and Locale
  • 56b65e4: 8267569: java.io.File.equals contains misleading Javadoc
  • 508cec7: 8267521: Post JEP 411 refactoring: maximum covering > 50K
  • 40d23a0: 8267543: Post JEP 411 refactoring: security

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@openjdk openjdk bot added the ready Pull request is ready to be integrated label Jun 2, 2021
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lgxbslgx commented Jun 2, 2021

@vicente-romero-oracle Thanks for your review. Could I get your help to sponsor this patch?

/integrate

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Your change (at version 5f4f5bb) is now ready to be sponsored by a Committer.

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/sponsor

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@vicente-romero-oracle Thanks for your review. Could I get your help to sponsor this patch?

/integrate

sure, done

@openjdk openjdk bot closed this Jun 2, 2021
@openjdk openjdk bot added integrated Pull request has been integrated and removed sponsor Pull request is ready to be sponsored ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jun 2, 2021
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openjdk bot commented Jun 2, 2021

@vicente-romero-oracle @lgxbslgx Since your change was applied there have been 4 commits pushed to the master branch:

  • e1462e7: 8267176: StandardDoclet should provide access to Reporter and Locale
  • 56b65e4: 8267569: java.io.File.equals contains misleading Javadoc
  • 508cec7: 8267521: Post JEP 411 refactoring: maximum covering > 50K
  • 40d23a0: 8267543: Post JEP 411 refactoring: security

Your commit was automatically rebased without conflicts.

Pushed as commit b7ac705.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

@lgxbslgx lgxbslgx deleted the JDK-8263642 branch June 2, 2021 17:26
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