[type.descriptions] (original) (raw)

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Many of the customization point objects in the library evaluate function call expressions with an unqualified name which results in a call to a program-defined function found by argument dependent name lookup ([basic.lookup.argdep]).

To preclude such an expression resulting in a call to unconstrained functions with the same name in namespace std, customization point objects specify that lookup for these expressions is performed in a context that includes deleted overloads matching the signatures of overloads defined in namespace std.

When the deleted overloads are viable, program-defined overloads need be more specialized ([temp.func.order]) or more constrained ([temp.constr.order]) to be used by a customization point object.

— end note