Compiler NPE in local-methods branch with recursive lambda

[Srikanth]

Thank you Jake Wharton.

This feature in its infancy. But I welcome such testing as you done 
since it has resulted in a well defined defect report: 
https://bugs.openjdk.java.net/browse/JDK-8234874

Thanks!
Srikanth

On 27/11/19 2:11 AM, Jake Wharton wrote:
> Whoops. Sent the version with the predicate-capturing 'if' already removed!
> The full reproducer is:
>
> interface Node {
>    List<Node> getNodes();
>
>    static boolean any(Node root, Predicate<Node> predicate) {
>      boolean hasMatch(Node node) {
>        if (predicate.test(node)) return true;
>        return node.getNodes().stream().anyMatch(n -> hasMatch(n));
>      }
>      return hasMatch(root);
>    }
> }
>
> On Tue, Nov 26, 2019 at 3:39 PM Jake Wharton <jakewharton at gmail.com> wrote:
>
>> With hg revision 4a43a5fc2c4a, given the following pared-down input:
>>
>> interface Node {
>>    List<Node> getNodes();
>>
>>    static boolean any(Node root, Predicate<Node> predicate) {
>>      boolean hasMatch(Node node) {
>>        return node.getNodes().stream().anyMatch(n -> hasMatch(n));
>>      }
>>      return hasMatch(root);
>>    }
>> }
>>
>> Compilation causes:
>>
>> java.lang.NullPointerException
>> at jdk.compiler/com.sun.tools.javac.jvm.Code.emitop0(Code.java:570)
>> at
>> jdk.compiler/com.sun.tools.javac.jvm.Items$LocalItem.load(Items.java:399)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genArgs(Gen.java:885)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitApply(Gen.java:1851)
>> at
>> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1736)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:860)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitReturn(Gen.java:1814)
>> at
>> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCReturn.accept(JCTree.java:1648)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:597)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:632)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:618)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStats(Gen.java:669)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitBlock(Gen.java:1080)
>> at
>> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1029)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:597)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:632)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genMethod(Gen.java:950)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitMethodDef(Gen.java:913)
>> at
>> jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:875)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:597)
>> at jdk.compiler/com.sun.tools.javac.jvm.Gen.genClass(Gen.java:2391)
>> at
>> jdk.compiler/com.sun.tools.javac.main.JavaCompiler.genCode(JavaCompiler.java:757)
>> at
>> jdk.compiler/com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1677)
>> at
>> jdk.compiler/com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1645)
>> at
>> jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:973)
>> at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:318)
>> at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:176)
>> at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:57)
>> at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:43)
>>
>> The problem seems to be a combination of the fact that the local method
>> captures 'predicate' and recursively invokes itself from a lambda. Removing
>> the 'if' will result in successful compilation. Replacing the stream with a
>> for-each will result in successful compilation.
>>