In other languages we can use the logical-or shortcut. If maybeSomeNumber() 
returns null, assign a default value of 2:

value = maybeSomeNumber() || 2

In Dart we can’t do this because the expression needs to be a boolean (“the 
operands of the || operator must be assignable to bool").
That’s why the ?? operator exists:

var value = maybeSomeNumber() ?? 2;