tmp/tmpi_jdczzx/{from.md → to.md}
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### General <a id="over.match.general">[[over.match.general]]</a>
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Overload resolution is a mechanism for selecting the best function to
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call given a list of expressions that are to be the arguments of the
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call and a set of *candidate functions* that can be called based on the
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context of the call. The selection criteria for the best function are
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the number of arguments, how well the arguments match the
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parameter-type-list of the candidate function, how well (for non-static
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member functions) the object matches the object parameter, and certain
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other properties of the candidate function.
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[*Note 1*: The function selected by overload resolution is not
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guaranteed to be appropriate for the context. Other restrictions, such
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as the accessibility of the function, can make its use in the calling
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context ill-formed. — *end note*]
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Overload resolution selects the function to call in seven distinct
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contexts within the language:
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- invocation of a function named in the function call syntax
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[[over.call.func]];
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- invocation of a function call operator, a pointer-to-function
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conversion function, a reference-to-pointer-to-function conversion
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function, or a reference-to-function conversion function on a class
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object named in the function call syntax [[over.call.object]];
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- invocation of the operator referenced in an expression
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[[over.match.oper]];
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- invocation of a constructor for default- or direct-initialization
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[[dcl.init]] of a class object [[over.match.ctor]];
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- invocation of a user-defined conversion for copy-initialization
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[[dcl.init]] of a class object [[over.match.copy]];
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- invocation of a conversion function for initialization of an object of
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a non-class type from an expression of class type [[over.match.conv]];
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and
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- invocation of a conversion function for conversion in which a
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reference [[dcl.init.ref]] will be directly bound [[over.match.ref]].
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Each of these contexts defines the set of candidate functions and the
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list of arguments in its own unique way. But, once the candidate
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functions and argument lists have been identified, the selection of the
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best function is the same in all cases:
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- First, a subset of the candidate functions (those that have the proper
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number of arguments and meet certain other conditions) is selected to
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form a set of viable functions [[over.match.viable]].
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- Then the best viable function is selected based on the implicit
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conversion sequences [[over.best.ics]] needed to match each argument
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to the corresponding parameter of each viable function.
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If a best viable function exists and is unique, overload resolution
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succeeds and produces it as the result. Otherwise overload resolution
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fails and the invocation is ill-formed. When overload resolution
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succeeds, and the best viable function is not accessible
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[[class.access]] in the context in which it is used, the program is
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ill-formed.
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Overload resolution results in a *usable candidate* if overload
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resolution succeeds and the selected candidate is either not a function
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[[over.built]], or is a function that is not deleted and is accessible
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from the context in which overload resolution was performed.
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