12 Overloading [over]

12.4 Overload resolution [over.match]

12.4.2 Candidate functions and argument lists [over.match.funcs]

12.4.2.7 Initialization by conversion function for direct reference binding [over.match.ref]

1
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Under the conditions specified in [dcl.init.ref], a reference can be bound directly to the result of applying a conversion function to an initializer expression.
Overload resolution is used to select the conversion function to be invoked.
Assuming that “reference to cv1 T” is the type of the reference being initialized, and “cv S” is the type of the initializer expression, with S a class type, the candidate functions are selected as follows:
  • (1.1)
    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 “lvalue reference to cv2 T2” (when initializing an lvalue reference or an rvalue reference to function) or “cv2 T2” or “rvalue reference to cv2 T2” (when initializing an rvalue reference or an lvalue reference to function), where “cv1 T” is reference-compatible with “cv2 T2”, are candidate functions.
    For direct-initialization, those explicit conversion functions that are not hidden within S and yield type “lvalue reference to cv2 T2” (when initializing an lvalue reference or an rvalue reference to function) or “rvalue reference to cv2 T2” (when initializing an rvalue reference or an lvalue reference to function), where T2 is the same type as T or can be converted to type T with a qualification conversion, are also candidate functions.
2
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The argument list has one argument, which is the initializer expression.
[Note 1:
This argument will be compared against the implicit object parameter of the conversion functions.
— end note]