Ambiguous method call bug

Similar to this we've been getting a ambiguous method call error squiggly in IntelliJ IDEA (2018.2.7, but for a while and many different versions.)

Beam has a static method and an instance method for some of its types, mainly `FlatMapElements`

public static <InputT, OutputT> FlatMapElements<InputT, OutputT> via(
    SimpleFunction<? super InputT, ? extends Iterable<OutputT>> fn) {
........
  return new FlatMapElements<>(wrapped, fn, inputType, outputType);
}


public static <OutputT> FlatMapElements<?, OutputT> into(
    final TypeDescriptor<OutputT> outputType) {
  return new FlatMapElements<>(null, null, null, outputType);
}

public <NewInputT> FlatMapElements<NewInputT, OutputT> via(
    SerializableFunction<NewInputT, ? extends Iterable<OutputT>> fn) {
  return new FlatMapElements<>((Contextful) Contextful.fn(fn), fn, TypeDescriptors.inputOf(fn), outputType);
}

Here is a sample that triggers the error:

@Test
public void not_an_error() {
  final TestPipeline pipeline = TestPipeline.fromOptions(AwsPipelineTestOptions.getOptions());


  final PCollection<Integer> inputs = pipeline.apply(TestStream.create(VarIntCoder.of())
      .addElements(3, 5, 7)
      .advanceWatermarkToInfinity());

  PAssert.that(inputs.apply(MapElements.via(new SimpleFunction<Integer, Integer>() {
    @Override
    public Integer apply(final Integer input) {
      return input;
    }
  }))).containsInAnyOrder(3, 5, 7);


  final PCollection<Integer> result =
      inputs.apply(FlatMapElements.via(new SimpleFunction<Integer, ImmutableList<Integer>>() {
        @Override
        public ImmutableList<Integer> apply(final Integer input) {
          return ImmutableList.of(1 * input, 3 * input);
        }
      }));

  PAssert.that(result).containsInAnyOrder(3, 9, 5, 15, 7, 21);
}

The IDE complains with a squiggly on

but the code compiles fine and the test passes. (notice that MapElements doesn't error but has the same type shape...)