Safe call on a non-null receiver will have nullable type in future releases.

Safe_call_on_a_non-null_receiver_will_have_nullable_type_in_future_releases.md

Safe call on a non-null receiver will have nullable type in future releases.

Right now safe call on non nullable receiver has not null type:

"hello"?.length has type Int

In future releases all safe calls will have nullable type:

"hello"?.length will have type Int?

用意:

1. 不要濫用 nullable type and safe call(?.) : 如果確定是 non-null object 請直接用 dot call 提取 property 或 呼叫 function
2. safe call 性質傳遞 : 不論是否 non-null object 用 safe call 提取 property 或 function return 也直接感染 nullable type