Issue1976-constraints3.agda:20,3-15
Ambiguous projection F.
It could refer to any of
  ShouldFail._.F (introduced at Issue1976-constraints3.agda:16,8-8)
  ShouldFail._.F (introduced at Issue1976-constraints3.agda:17,8-8)
when checking that the clause F test = Set has type M.R B
