When is ADL applied?

Question

There are 3 examples:

I.

typedef int foo;

namespace B
{
    struct S
    {
        operator int(){ return 24; }
    };
        int foo(B::S s){ retu         


        

Answer 1

This Standard paragraph clarifies, and even has an example very much like your first example.

3.4.1/3:

The lookup for an unqualified name used as the postfix-expression of a function call is described in 3.4.2 [basic.lookup.argdep]. [Note: For purposes of determining (during parsing) whether an expression is a postfix-expression for a function call, the usual name lookup rules apply. The rules in 3.4.2 have no effect on the syntactic interpretation of an expression. For example,

typedef int f;
namespace N {
  struct A {
    friend void f(A &);
    operator int();
    void g(A a) {
      int i = f(a);    // f is the typedef, not the friend
                       // function: equivalent to int(a)
    }
  };
}

Because the expression is not a function call, the argument-dependent name lookup (3.4.2) does not apply and the friend function f is not found. -end note]