public WorkResult execute(SwiftCompileSpec spec) {
        final boolean didRemove;
        if (spec.isIncrementalCompile()) {
            didRemove = deleteOutputsForRemovedSources(spec);
        } else {
            didRemove = cleanPreviousOutputs(spec);
        }

        WorkResult compileResult = compile(spec);
        return WorkResults.didWork(didRemove || compileResult.getDidWork());
    }

            iterator.remove();
            didRemove(lastElement);
            getEventRegister().fireObjectRemoved(lastElement);
            lastElement = null;
        }

        @Override
        public void set(T t) {
            assertMutable("listIterator().set(T)");
            assertCanAdd(t);
            iterator.set(t);
            didRemove(lastElement);

        this.outputFileSuffix = outputFileSuffix;
    }

    @Override
    public WorkResult execute(T spec) {
        boolean didRemove = deleteOutputsForRemovedSources(spec);
        boolean didCompile = compileSources(spec);
        return WorkResults.didWork(didRemove || didCompile);
    }

    private boolean compileSources(T spec) {
        if (spec.getSourceFiles().isEmpty()) {
            return false;