我想看一个例子，其中在整个postfix-expression的上下文中查找conversion-type-id

Question

In [basic.lookup.classref]/7 (C++14) we have (emphasis is mine):

If the id-expression is a conversion-function-id , its conversion-type-id is first looked up in the class of the object expression and the name, if found, is used. Otherwise it is looked up in the context of the entire postfix-expression . In each of these lookups, only names that denote types or templates whose specializations are types are considered.

I don't understand the need for the Otherwise above. Therefore, I'd like to see an example, where the conversion-type-id is looked up in the context of the entire postfix-expression.

Answer 1

Something like this :

struct C {
    operator int() { return 42; }
};

typedef int X;

int main() {
  C c;
  c.operator X();  // calls c.operator int();
}

Clearly, the name X is not found in class C , but is found in the context of the expression where it's used.