1 @safe unittest
2 {
3     struct CustomString
4     {
5     @safe:
6         string _impl;
emptyCustomString7         @property bool empty() const { return !_impl.length; }
8     }
9 
find(CustomString a,CustomString b)10     CustomString find(CustomString a, CustomString b)
11     {
12         return CustomString.init;
13     }
14 
15     auto r = find(CustomString("a"), CustomString("b"));
16     assert(r.empty);
17 }
18