error[E0432]: unresolved import `a::b1::C1`
  --> $DIR/use-nested-groups-error.rs:19:14
   |
LL | use a::{b1::{C1, C2}, B2};
   |              ^^ no `C1` in `a::b1`. Did you mean to use `C2`?

error: aborting due to previous error

For more information about this error, try `rustc --explain E0432`.