Remapping an overridden method to Yarn fails

[natanfudge]

Example: https://crashy.net/Re4wmtN5mxBAd7GC1xYl
This happens because intermediary doesn't provide mappings to overridden methods, because technically a program that is remapping Minecraft can remap the parent class and all of the inheriting methods with it with only the mappings of the parent class.

A solution would need to fill in the blanks, or at least figure out which classes inherit which.