never-never land
noun [ U ] uk/ˌnev.əˈnev.ə ˌlænd/ us/ˌnev.ɚˈnev.ɚ ˌlænd/
世外桃源，理想乐土
an imaginary place where everything is pleasant or perfect in a way that is impossible to achieve in real life
If he thinks we can get this done by next week, he's living in never-never land. 如果他认为我们下周就能把这项工作完成的话，那他简直是在妄想。