Under the conditions specified in [dcl.init], as part of an initialization of an object of nonclass type, a conversion function can be invoked to convert an initializer expression of class type to the type of the object being initialized. Overload resolution is used to select the conversion function to be invoked. Assuming that “cv1 T” is the type of the object being initialized, and “cv S” is the type of the initializer expression, with S a class type, the candidate functions are selected as follows:
The conversion functions of S and its base classes are considered. Those non-explicit conversion functions that are not hidden within S and yield type T or a type that can be converted to type T via a standard conversion sequence ([over.ics.scs]) are candidate functions. For direct-initialization, those explicit conversion functions that are not hidden within S and yield type T or a type that can be converted to type T with a qualification conversion ([conv.qual]) are also candidate functions. Conversion functions that return a cv-qualified type are considered to yield the cv-unqualified version of that type for this process of selecting candidate functions. Conversion functions that return “reference to cv2 X” return lvalues or xvalues, depending on the type of reference, of type “cv2 X” and are therefore considered to yield X for this process of selecting candidate functions.
The argument list has one argument, which is the initializer expression. [ Note: This argument will be compared against the implicit object parameter of the conversion functions. — end note ]