> [temp.res.general]/6.4 is not talking about substitution failure,
> it's talking about satisfaction checks of atomic constraints
> being ill-formed (a situation that arises when substitution
> succeeds but does not produce a constant expression of
> type bool). If a satisfaction check of A is performed, then
> the program is just ill-formed (diagnostic required).

Thank you for this contribution.
I wonder the term 'satisfaction check' is just twice in the standard,
both occurrences in [temp.res.general]/6.4.
Might you please help me with any reference to other parts
supporting this terminology ?


> Since CWG2461 there's no equivalent of [expr.prim.req.general]/5 for
> atomic constraints. (Maybe there should be; I'm not entirely convinced
> the removal was intentional.)

Thank you for this comment, too.
Do you have idea about any effective removal on it ?
Restoring/adding it might be a topic.