How does VBA determine whether the default property is implicitly used or not?

Question

VBA determines that IsEmpty(Range("A1")) implicitly uses the default property, so the expression is the same as IsEmpty(Range("A1").[_Default]) . On the other hand, VBA determines that TypeName(Range("A1")) does not use the default property, so the expression is different from TypeName(Range("A1").[_Default]) .

Question

How does VBA determine whether the default property is implicitly used or not?

Answer 1

IsEmpty需要一个数据值，而不是一个对象类型，所以你会得到隐式的 Let-coercion，它会调用默认属性来尝试获取一个简单的数据值。