NPE when compiling simple enum class with lambda expressions

[vegegoku]

Describe the bug
I have a simple enum java class that define an inner Functional interface, the interface is used a constructor argument for the enum class, enum entires are defined passing a lambada expression of that functional interface.

compiling with j2cl throws a NullPointerException.

To Reproduce
we can reproduce this issue in using the hello world sample:

• add the following class next to the HelloWorld.java

package com.google.j2cl.samples.helloworldlib;

public enum Unit{
    px(value -> value + "px"),
    em(value -> value + "em");

    private final UnitFormatter unitFormatter;

    Unit(UnitFormatter unitFormatter) {
        this.unitFormatter = unitFormatter;
    }

    public String of(Number value) {
        return unitFormatter.format(value);
    }

    @FunctionalInterface
    public interface UnitFormatter{
        String format(Number value);
    }
}

• try to transpile the Hello world sample

this will produce an exception with the following stack trace

ures.wrapAndThrowUnchecked(Futures.java:1546)
        at com.google.common.util.concurrent.Futures.getUnchecked(Futures.java:1532)
        at com.google.j2cl.transpiler.J2clTranspiler.transpile(J2clTranspiler.java:111)
        at com.google.j2cl.transpiler.BazelJ2clBuilder.run(BazelJ2clBuilder.java:74)
        at com.google.j2cl.bazel.BazelWorker.processRequest(BazelWorker.java:62)
        at com.google.j2cl.bazel.BazelWorker.execute(BazelWorker.java:116)
        at com.google.j2cl.bazel.BazelWorker.runPersistentWorker(BazelWorker.java:98)
        at com.google.j2cl.bazel.BazelWorker.start(BazelWorker.java:71)
        at com.google.j2cl.transpiler.BazelJ2clBuilder.main(BazelJ2clBuilder.java:158)
Caused by: java.lang.NullPointerException
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:1617)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:647)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:1384)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:627)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convertLambdaBody(CompilationUnitBuilder.java:1037)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:1023)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:631)
        at java.base/java.util.stream.ReferencePipeline$3$1.accept(Unknown Source)
        at java.base/java.util.Iterator.forEachRemaining(Unknown Source)
        at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Unknown Source)
        at java.base/java.util.stream.AbstractPipeline.copyInto(Unknown Source)
        at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
        at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(Unknown Source)
        at java.base/java.util.stream.AbstractPipeline.evaluate(Unknown Source)
        at java.base/java.util.stream.ReferencePipeline.collect(Unknown Source)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convertArguments(CompilationUnitBuilder.java:1501)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:299)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:208)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:190)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.convert(CompilationUnitBuilder.java:177)
        at com.google.j2cl.frontend.CompilationUnitBuilder$ASTConverter.access$100(CompilationUnitBuilder.java:133)
        at com.google.j2cl.frontend.CompilationUnitBuilder.buildCompilationUnit(CompilationUnitBuilder.java:1914)
        at com.google.j2cl.frontend.CompilationUnitBuilder.lambda$build$0(CompilationUnitBuilder.java:1936)
        at java.base/java.util.stream.ReferencePipeline$3$1.accept(Unknown Source)
        at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(Unknown Source)
        at java.base/java.util.stream.AbstractPipeline.copyInto(Unknown Source)
        at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
        at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(Unknown Source)
        at java.base/java.util.stream.AbstractPipeline.evaluate(Unknown Source)
        at java.base/java.util.stream.ReferencePipeline.collect(Unknown Source)
        at com.google.j2cl.frontend.CompilationUnitBuilder.build(CompilationUnitBuilder.java:1938)
        at com.google.j2cl.transpiler.J2clTranspiler.convertUnits(J2clTranspiler.java:141)
        at com.google.j2cl.transpiler.J2clTranspiler.transpileImpl(J2clTranspiler.java:125)
        at com.google.j2cl.transpiler.J2clTranspiler.lambda$transpile$0(J2clTranspiler.java:110)
        at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.base/java.lang.Thread.run(Unknown Source)
---8<---8<--- End of log snippet, 791 chars omitted ---8<---8<---
Target //src/main/java/com/google/j2cl/samples/helloworld:helloworld failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 1.388s, Critical Path: 1.15s, Remote (0.00% of the time): [queue: 0.00%, setup: 0.00%, process: 0.00%]
INFO: 2 processes: 1 local, 1 worker.
FAILED: Build did NOT complete successfully

for some reason the CurrentType is being Null in the CompilationUnitBuilder during the process of converting the lambda expression body.

expanding the lamda to anonymous classes works.

[rluble]

Thanks for the clear repro.

[rluble]

Fixed by 948bfb8. Please verify.

[vegegoku]

Fix confirmed, it is working now. 👍