It would have been trivial to make the error for non-bool constraint in
satisfy_atom unconditional, but that didn't give context for the error or
printing with the dependent form and template arguments. So I changed a
couple of places so that, when a hard error is encountered during quiet
substitution/satisfaction, we go through again noisily; this builds up the
necessary context.
The similar change to tsubst_nested_requirement does not build up the
necessary context; rather than try to fix that now I changed
get_constraint_error_location to give up and use input_location if there's
no CONSTR_CONTEXT. In the case of concepts-pr67697.C, we still have a good
source location because the NESTED_REQ has a correct EXPR_LOCATION, but this
patch doesn't improve context printing for this case as it does for the
above.
gcc/cp/ChangeLog
2020-03-24 Jason Merrill <jason@redhat.com>
PR c++/94186
* constraint.cc (constraint_satisfaction_value): Repeat noisily on
error.
(tsubst_nested_requirement): Likewise.
(get_constraint_error_location): Allow missing context.
(diagnose_atomic_constraint): Diagnose non-bool constraint here.
(satisfy_atom): Not here. Only diagnose non-constant when noisy.
