What do you mean by that? Sure this is some kind of failure as the column type extracted from the column comment isn't known to Doctrine (anymore). The question is what do in this case. You could throw an exception here (which is the current behaviour) or fall back to the native database type (which is what this PR does).

A possible use case:

1. Create table with custom column type.
2a. Decide you don't need the custom type for the particular column anymore and switch to another.
2b. Decide you refeactor the custom type and you another type name for it or switch to another custom type.
3. Update schema.

Currently updating the schema will fail as it tries to extract a non existing Doctrine type from the column comment. In general reverse engineering custom column types that are not known to Doctrine will fail.

I guess this is a matter of preference here how Doctrine shall behave in such a case.

Any opinions?