Julie Tibshirani 8454cfc1b2 Move validation from FieldTypeLookup to MapperMergeValidator. (#39814)
This commit consolidates more mapping validation logic into the same class.
`FieldTypeLookup` is now a bit simpler, and has the sole responsibility of quickly
resolving field names to their types.

I have a broader refactor planned around mapping merge validation, but this
change should at least be a step in the right direction.
2019-03-08 18:05:21 -08:00
..