nonesuch
Synopsis
Declared in <folly/Traits.h>
struct nonesuch;Description
A tag type which traits may use to indicate lack of a result type.
Similar to void in that no values of this type may be constructed. Different from void in that no functions may be defined with this return type and no complete expressions may evaluate with this expression type.
mimic: std::experimental::nonesuch, Library Fundamentals TS v2