Hi Bruno,
OK, yes. I now remember we mailed about this. You are right, we cannot check the concepts here (as long as the concept check is not variant aware ;-) ).
So "as early as possible" is then as soon as variants are resolved. This probably also accounts for dimension checks etc. OK for me.

Yes I wanted to check the influence on early/later checks for compiler messages, but did not do that yet.

Regards, Barend