I am having trouble understanding some code I saw of the form:

fun myfun: Boolean {
  return foo?.stringProperty.isNullOrEmpty()
}

It seems to me that this would return

null

, which is not

Boolean

when

foo

is

null

. Why is the above code legal?

Note the lack of

?

before the final function call.

isNullOrEmpty

is an extension on a nullable type, so it can be called with a null receiver and will still return a non-null value.

isNullOrEmpty is defined on a nullable type