presto-hive/src/main/java/io/prestosql/plugin/hive/coercions/TypeCoercer.java/TypeCoercer/TypeCoercer
class TypeCoercer:    protected TypeCoercer(F fromType, T toType)
    {
        this.fromType = requireNonNull(fromType);
        this.toType = requireNonNull(toType);
    }