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8261205: AssertionError: Cannot add metadata to an intersection type #4095

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vicente-romero-oracle
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@vicente-romero-oracle vicente-romero-oracle commented May 18, 2021

Please review this PR which is adding a field to JCVariableDecl, the need I see for this is that when we declare a local variable using var as in:

import java.lang.annotation.ElementType;
import java.lang.annotation.Target;

@Target({ElementType.TYPE_USE, ElementType.LOCAL_VARIABLE})
@interface A {}

class Test {
    void t() {
        @A var c = g(1, 1L);
    }

    <X> X g(X a, X b) {
        return a;
    }
}

the only clue the compiler has to know that the local variable was declared using var is that field JCVariableDecl::vartype is null, but this field is set to an inferred type at some point during the compilation and from that point on there is no way to know for sure that the original AST had a var or not. Unfortunately there is code that keeps asking if the local variable was implicitly typed or not, after field JCVariableDecl::vartype has been written, and thus making uninformed decisions as in: TypeAnnotations.TypeAnnotationPositions::visitVarDef, where the compiler is implementing a portion of section: 9.7.4 Where Annotations May Appear of the spec (JLS16). In particular the portion that defines how to deal with annotations applied to local variables declared with var.

The test case above is interesting because the same annotation works as a declaration annotation and as a type annotation. If it were only a type annotation then the compiler would have issued an error before getting to TypeAnnotations.TypeAnnotationPositions::visitVarDef, precisely at Check::validateAnnotation, see that Check::getApplicableTargets has a special case for local variables declared using var. But again given that the annotation in the example above is applicable as a type and as a declaration annotation, it will seep down to the metadata info associated to the local variable symbol, and that is fine. What is not kosher is that as the compiler has no clue that the AST was originally declared using var that it then tries to type-annotate the type of the local variable. This change is thus making sure that that information is preserved.

This patch is also renaming a method in JCVariableDecl, its previous name was isImplicitlyTyped which was basically checking if the vartype field was null and was renamed to nullVarType, hasNullVarType could be an option too, and a new method was added: declaredUsingVar which won't change its returned value during the lifetime of a JCVariableDecl AST.

TIA


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Issue

  • JDK-8261205: AssertionError: Cannot add metadata to an intersection type

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Checkout this PR locally:
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Update a local copy of the PR:
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👋 Welcome back vromero! 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 May 18, 2021
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@vicente-romero-oracle The following label will be automatically applied to this pull request:

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mlbridge bot commented May 18, 2021

Webrevs

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@mcimadamore mcimadamore left a comment

What happens if we just use declaredUsingVar everywhere? Shouldn't that be the "right" way to do it?

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vicente-romero-oracle commented May 18, 2021

What happens if we just use declaredUsingVar everywhere? Shouldn't that be the "right" way to do it?

yep I also considered that but then realized that parameters of implicit lambdas also have its vartype set to null until the compiler infers a type for them, so the implicitly-typed set and the declared using var set have a non-empty intersection but they are not identical, so I preferred to keep the previous API, just with a tweak in the method name, and add a new method to reflect the fact that there is a difference between being explicitly typed and being declared using var.

So thinking again about the naming I think that I can let the method JCVarDeclaration::isImplicitlyTyped untouched and just add the new method declaredUsingVar or with name isDeclaredUsingVar, what do you think?

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vicente-romero-oracle commented May 18, 2021

I have uploaded a new commit, after an offline comment from Maurizio, he is correct that: given that lambda parameters also have a null type, they will be classified as "declared with var". This commit gets back to the original method name JCVarDeclaration::isImplicitlyTyped which will be true for local variables declared with var and for parameters of implicit lambdas.

@@ -44,7 +44,6 @@
import static com.sun.tools.javac.code.Kinds.*;
import static com.sun.tools.javac.code.Kinds.Kind.*;
import static com.sun.tools.javac.code.TypeTag.TYPEVAR;
import static com.sun.tools.javac.tree.JCTree.Tag.VARDEF;
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the import removal changes have been introduced by intelliJ

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@mcimadamore mcimadamore left a comment

Looks better - one question: what about var with annotations and lambda parameters? E.g. you can probably construct a similar example involving a lambda parameter - is this fix enough, or would the code path be slightly different?

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vicente-romero-oracle commented May 19, 2021

Looks better - one question: what about var with annotations and lambda parameters? E.g. you can probably construct a similar example involving a lambda parameter - is this fix enough, or would the code path be slightly different?

good catch! I have modified the patch to include the case for lambda parameters declared with var, I also removed the initial test and added a new one that not only makes sure that the code compiles, it also checks that no type annotations are represented in the class file

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@mcimadamore mcimadamore left a comment

Looks good - but I think there's an issue in the test?


class Test {
void kaa() {
//@A var c = g(1, 1L);
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Is this meant to be commented out?

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Ah ok, I see this is fixed now

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yep, thanks for the review

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@mcimadamore mcimadamore left a comment

Thumbs up!

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openjdk bot commented May 20, 2021

@vicente-romero-oracle 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:

8261205: AssertionError: Cannot add metadata to an intersection type

Reviewed-by: mcimadamore

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At the time when this comment was updated there had been no new commits pushed to the master branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential automatic rebasing, please check the documentation for the /integrate command for further details.

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@openjdk openjdk bot added the ready Pull request is ready to be integrated label May 20, 2021
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vicente-romero-oracle commented May 20, 2021

/integrate

@openjdk openjdk bot closed this May 20, 2021
@openjdk openjdk bot added integrated Pull request has been integrated and removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels May 20, 2021
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openjdk bot commented May 20, 2021

@vicente-romero-oracle Since your change was applied there have been 10 commits pushed to the master branch:

  • 7b98400: 8267348: Rewrite gc/epsilon/TestClasses.java to use Metaspace with less classes
  • ca93399: 8267235: [macos_aarch64] InterpreterRuntime::throw_pending_exception messing up LR results in crash
  • b7b6acd: 8267481: Make sure table row has correct number of cells
  • f67847f: 8267396: Avoid recording "pc" in unhandled oops detector for better performance
  • 878d1b3: 8267434: Remove LinkOutput[Impl]
  • fc7f0a3: 8267480: Explicitly problemlist all runtime/os/TestTracePageSizes.java tests on linux-aarch64 to reduce noise
  • 9425d3d: 8261880: Change nested classes in java.base to static nested classes where possible
  • 459abd5: 8267219: Javadoc method summary breaks when {@inheritdoc} from an empty parent
  • aba2265: 8260267: ZGC: Reduce mark stack usage
  • f979523: 8267463: Problemlist runtime/os/TestTracePageSizes.java on linux-aarch64 to reduce noise

Your commit was automatically rebased without conflicts.

Pushed as commit 81f39ed.

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

@vicente-romero-oracle vicente-romero-oracle deleted the JDK-8261205 branch May 20, 2021
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