Comparison of incorrectly annotated classes hides original problems

[psfinaki]

Discovered when playing with F# comparison rules.

Look:

This is the correct error. But once I add a comparison test, the error changes and becomes confusing:

Expected behavior

Both errors show up.

Actual behavior

The new error hides the original one.

Known workarounds

Don't do this.

Related information

This is pretty much an edge case and this bug is worth giving it attention only if hides some more serious issue.

Shot in the dark, @auduchinok do you think this can be related to parser rules and/or easily fixed there?