---
assert((a as? String)?.length == 5)
        | |            |      |
        | |            |      false
        | |            4
        | test
        test
---
---
assert((a as? String)?.length == 5)
        | |            |      |
        | |            |      false
        | |            null
        | null
        1
---
---
requireNotNull(a as? String)
               | |
               | null
               1
---
