If there is no requirement for a destructor for a type, according to _N2914_.14.11.2.1 [temp.archetype.assemble] paragraph 5 its archetype will have a deleted destructor. As a result, several examples in the current wording are ill-formed:

• _N2914_.14.10.2 [concept.map] paragraph 11: the add function.

• _N2914_.14.10.3.1 [concept.member.lookup] paragraph 3: the f function. (Also missing the copy constructor requirement.)

• _N2914_.14.10.3.1 [concept.member.lookup] paragraph 5: the h function. (Also missing the copy constructor requirement.)

• _N2914_.14.11.1 [temp.req] paragraph 3: the f function.

• _N2914_.14.11.1.1 [temp.req.sat] paragraph 6: the g function. (Also missing the copy constructor requirement.)

• _N2914_.14.11.2 [temp.archetype] paragraph 15: the distance function.

• _N2914_.14.11.2.1 [temp.archetype.assemble] paragraph 2: the foo function.

• _N2914_.14.11.2.1 [temp.archetype.assemble] paragraph 3: the f function.

• _N2914_.14.11.4 [temp.constrained.inst] paragraph 4: needed for difference_type.

One possibility would be to add the destructor requirement directly in these examples. Another might be to use std::CopyConstructible instead of a local concept. Yet another would be to consider an implicit requirement for a destructor for std::Returnable and std::VariableType.