Given a concept and an unconstrained template, e.g.,

    auto concept HasFoo<typename T> {
      void foo(T&);
    }

    template<typename T>
    struct SomeThing {
      void bar(){}
    };

how can one write a concept map template that adapts all specializations of SomeThing to concept HasFoo? Because a concept map template is a constrained context, referring to SomeThing violates the prohibition against using a specialization of an unconstrained template.

Surrounding the entire concept map template with late_check would appear not to work; the location of the late_check is in the unconstrained context, and late_check is ignored in unconstrained contexts.

One possibility would be to allow late_check to appear in the concept_map syntax.