presto-hive/src/main/java/io/prestosql/plugin/hive/HiveCoercionPolicy.java/HiveCoercionPolicy/canCoerceForMap
class HiveCoercionPolicy:    private boolean canCoerceForMap(HiveType fromHiveType, HiveType toHiveType)
    {
        if (!fromHiveType.getCategory().equals(Category.MAP) || !toHiveType.getCategory().equals(Category.MAP)) {
            return false;
        }
        HiveType fromKeyType = HiveType.valueOf(((MapTypeInfo) fromHiveType.getTypeInfo()).getMapKeyTypeInfo().getTypeName());
        HiveType fromValueType = HiveType.valueOf(((MapTypeInfo) fromHiveType.getTypeInfo()).getMapValueTypeInfo().getTypeName());
        HiveType toKeyType = HiveType.valueOf(((MapTypeInfo) toHiveType.getTypeInfo()).getMapKeyTypeInfo().getTypeName());
        HiveType toValueType = HiveType.valueOf(((MapTypeInfo) toHiveType.getTypeInfo()).getMapValueTypeInfo().getTypeName());
        return (fromKeyType.equals(toKeyType) || canCoerce(fromKeyType, toKeyType)) &&
                (fromValueType.equals(toValueType) || canCoerce(fromValueType, toValueType));
    }