DifferentNameButSame gives invalid suggestion on an inner class new instance

[ZacSweers]

Description of the problem / feature request:

Given this snippet, the DifferentNameButSame check warns

ServerFeatureFlagProcessor processor = new ServerFeatureFlagProcessor();
// Fails on this line
ServerFeatureFlagProcessor.TestBackdoor testBackdoor = processor.new TestBackdoor();

Suggesting this, which is invalid syntax

error: [DifferentNameButSame] This type is referred to in different ways within this file, which may be confusing.
    ServerFeatureFlagProcessor.TestBackdoor testBackdoor = processor.new TestBackdoor();
                                                                         ^
    (see https://errorprone.info/bugpattern/DifferentNameButSame)
  Did you mean 'ServerFeatureFlagProcessor.TestBackdoor testBackdoor = processor.new ServerFeatureFlagProcessor.TestBackdoor();'?

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

The above snippet should be fairly explanatory

What version of Error Prone are you using?

2.5.0

[cushon]

(This isn't fixed yet, but I added a repro in 0b7015e)