Annex D (normative) Compatibility features [depr]

D.12 Requires paragraph [depr.res.on.required]

In addition to the elements specified in [structure.specifications], descriptions of function semantics may also contain a Requires: element to denote the preconditions for calling a function.
Violation of any preconditions specified in a function's Requires: element results in undefined behavior unless the function's Throws: element specifies throwing an exception when the precondition is violated.