NPE when using Arrays.isList inside of generic class

[GoogleCodeExporter]

What steps will reproduce the problem?

It may not be the minimal case but in my case I trimmed it down to the 
following:

1. Create class A which has @Inject on its ctor and gets arguments injected via 
GWT-gin.

2. Create enum State inside of A.

3. Create class StateMachine<E extends Enum<E>> (see below) and include a 
member variable StateMachine<State> b; in class A (can leave uninitialized).

4. StateMachine should look like this:

public class StateMachine<E extends Enum<E>> {
    private class StateConfig {
        public final Collection<E> states;

        @SuppressWarnings("unchecked")
        public StateConfig(E... states) {
            this.states = new ArrayList<E>(Arrays.asList(states));
        }
    }
}

GWT compile fails with NPE from Gin:
     [java] java.lang.NullPointerException
     [java]     at com.google.gwt.inject.rebind.util.KeyUtil.javaToGwtMethod(KeyUtil.java:222)
     [java]     at com.google.gwt.inject.rebind.binding.ProviderMethodBinding.setProviderMethod(ProviderMethodBinding.java:60)
     [java]     at com.google.gwt.inject.rebind.BindingsProcessor$GuiceBindingVisitor.visit(BindingsProcessor.java:926)
     [java]     at com.google.gwt.inject.rebind.BindingsProcessor$GuiceBindingVisitor.visit(BindingsProcessor.java:898)
     [java]     at com.google.inject.internal.ProviderInstanceBindingImpl.acceptTargetVisitor(ProviderInstanceBindingImpl.java:62)
     [java]     at com.google.gwt.inject.rebind.BindingsProcessor$GuiceElementVisitor.visit(BindingsProcessor.java:827)
     [java]     at com.google.gwt.inject.rebind.BindingsProcessor$GuiceElementVisitor.visit(BindingsProcessor.java:820)
     [java]     at com.google.inject.internal.BindingImpl.acceptVisitor(BindingImpl.java:93)
     [java]     at com.google.gwt.inject.rebind.BindingsProcessor.createBindingsForModules(BindingsProcessor.java:409)
     [java]     at com.google.gwt.inject.rebind.BindingsProcessor.process(BindingsProcessor.java:238)
     [java]     at com.google.gwt.inject.rebind.GinjectorGeneratorImpl.generate(GinjectorGeneratorImpl.java:76)
     [java]     at com.google.gwt.inject.rebind.GinjectorGenerator.generate(GinjectorGenerator.java:47)
     [java]     at com.google.gwt.core.ext.GeneratorExtWrapper.generate(GeneratorExtWrapper.java:48)
     [java]     at com.google.gwt.core.ext.GeneratorExtWrapper.generateIncrementally(GeneratorExtWrapper.java:60)
     [java]     at com.google.gwt.dev.javac.StandardGeneratorContext.runGeneratorIncrementally(StandardGeneratorContext.java:647)
     [java]     at com.google.gwt.dev.cfg.RuleGenerateWith.realize(RuleGenerateWith.java:41)
     [java]     at com.google.gwt.dev.shell.StandardRebindOracle$Rebinder.rebind(StandardRebindOracle.java:78)
     [java]     at com.google.gwt.dev.shell.StandardRebindOracle.rebind(StandardRebindOracle.java:268)
     [java]     at com.google.gwt.dev.shell.StandardRebindOracle.rebind(StandardRebindOracle.java:257)
     [java]     at com.google.gwt.dev.DistillerRebindPermutationOracle.getAllPossibleRebindAnswers(DistillerRebindPermutationOracle.java:91)
     [java]     at com.google.gwt.dev.jdt.WebModeCompilerFrontEnd.doFindAdditionalTypesUsingRebinds(WebModeCompilerFrontEnd.java:96)
     [java]     at com.google.gwt.dev.jdt.AbstractCompiler$Sandbox$CompilerImpl.process(AbstractCompiler.java:254)
     [java]     at org.eclipse.jdt.internal.compiler.Compiler.compile(Compiler.java:444)
     [java]     at com.google.gwt.dev.jdt.AbstractCompiler$Sandbox$CompilerImpl.compile(AbstractCompiler.java:173)
     [java]     at com.google.gwt.dev.jdt.AbstractCompiler$Sandbox$CompilerImpl.compile(AbstractCompiler.java:288)
     [java]     at com.google.gwt.dev.jdt.AbstractCompiler$Sandbox$CompilerImpl.access$400(AbstractCompiler.java:139)
     [java]     at com.google.gwt.dev.jdt.AbstractCompiler.compile(AbstractCompiler.java:588)
     [java]     at com.google.gwt.dev.jdt.BasicWebModeCompiler.getCompilationUnitDeclarations(BasicWebModeCompiler.java:97)
     [java]     at com.google.gwt.dev.jdt.WebModeCompilerFrontEnd.getCompilationUnitDeclarations(WebModeCompilerFrontEnd.java:52)
     [java]     at com.google.gwt.dev.jjs.JavaToJavaScriptCompiler.precompile(JavaToJavaScriptCompiler.java:569)
     [java]     at com.google.gwt.dev.jjs.JavaScriptCompiler.precompile(JavaScriptCompiler.java:33)
     [java]     at com.google.gwt.dev.Precompile.precompile(Precompile.java:284)
     [java]     at com.google.gwt.dev.Precompile.precompile(Precompile.java:233)
     [java]     at com.google.gwt.dev.Precompile.precompile(Precompile.java:145)
     [java]     at com.google.gwt.dev.Compiler.run(Compiler.java:232)
     [java]     at com.google.gwt.dev.Compiler.run(Compiler.java:198)
     [java]     at com.google.gwt.dev.Compiler$1.run(Compiler.java:170)
     [java]     at com.google.gwt.dev.CompileTaskRunner.doRun(CompileTaskRunner.java:88)
     [java]     at com.google.gwt.dev.CompileTaskRunner.runWithAppropriateLogger(CompileTaskRunner.java:82)
     [java]     at com.google.gwt.dev.Compiler.main(Compiler.java:177)

What version of the product are you using? On what operating system?
1.5, RHEL5 x64

Please provide any additional information below.

Tried to replace ... with [] - same error.

However if I replace Arrays.asList with manual loop, the error goes away:

this.states = new ArrayList<E>(states.length);
for(E state : states) {
  this.states.add(state);
}

Original issue reported on code.google.com by kamot...@gmail.com on 12 Mar 2012 at 7:55

[GoogleCodeExporter]

Darn, just realized that this is because of wrong import suggested 
automatically by Eclipse. Switching to java.util.Arrays fixes everything, 
please feel free to close this Issue. Or, consider it a request to add better 
messaging during NPE to save diagnostic time for issues like this (I wasted 3 
hours at least trying to localize this code).

Original comment by kamot...@gmail.com on 12 Mar 2012 at 8:03

[GoogleCodeExporter]

Thanks for the bug report (even though it turned out not to be such a big 
problem :). This code has already changed significantly in HEAD and I think 
there should be better error messages now if we can't resolve a type.

Original comment by aragos on 12 Mar 2012 at 8:09

• Changed state: Invalid