On Tuesday, April 15, 2025, Jason McKesson wrote:

There's a reason concepts are the only kind of template that can't be
specialized. It is *very* important to the integrity of the concepts
system that there's a single, fixed definition against which all
constrained templates can be tested. `concept_name<type>` should have
exactly and only one answer, and that answer must be the same
everywhere.

You would never get a "bad answer" though.

Translation units that don't include "HugeInt.hpp" won't ever make reference to the class 'HugeInt', and therefore it doesn't matter if the concept allows for HugeInt in some translation units but not in others.