ban-types: Refactor to function (#2550)
ban-types: Refactor to function (#2550)

[no-log] simple refactor
berickson1/tslint,mprobst/tslint,andy-ms/tslint,andy-hanson/tslint,berickson1/tslint,JoshuaKGoldberg/tslint,andy-hanson/tslint,IllusionMH/tslint,andy-hanson/tslint,palantir/tslint,palantir/tslint,mprobst/tslint,andy-ms/tslint,mprobst/tslint,IllusionMH/tslint,andy-ms/tslint,berickson1/tslint,palantir/tslint,JoshuaKGoldberg/tslint,JoshuaKGoldberg/tslint,IllusionMH/tslint