error: bound modifier `?` can only be applied to default traits like `Sized`
  --> $DIR/more_maybe_bounds.rs:16:20
   |
LL | fn bar<T: ?Sized + ?Trait2 + ?Trait1 + ?Trait4>(_: &T) {}
   |                    ^^^^^^^

error: bound modifier `?` can only be applied to default traits like `Sized`
  --> $DIR/more_maybe_bounds.rs:16:30
   |
LL | fn bar<T: ?Sized + ?Trait2 + ?Trait1 + ?Trait4>(_: &T) {}
   |                              ^^^^^^^

error: bound modifier `?` can only be applied to default traits like `Sized`
  --> $DIR/more_maybe_bounds.rs:16:40
   |
LL | fn bar<T: ?Sized + ?Trait2 + ?Trait1 + ?Trait4>(_: &T) {}
   |                                        ^^^^^^^

error: aborting due to 3 previous errors