Fails to generate code for maps within structs

[i]

Attempting to run easyjson on this file generates the following errors:

types.go

package types

type UUID string
type Meter string

type Thing struct {
  UUID   UUID
  Length Meter
}

type Response struct {
  Things map[UUID]Thing
}

errors:

# ezjson_test
./types_easyjson.go:27: undefined: types in types.UUID
./types_easyjson.go:27: undefined: types in types.Thing
./types_easyjson.go:36: cannot use key (type string) as type UUID in map index
./types_easyjson.go:63: cannot use v2_name (type UUID) as type string in argument to out.String