error[E0367]: `Drop` impl requires `T: Sized` but the struct it is implemented for does not
  --> $DIR/issue-17959.rs:11:6
   |
LL | impl<T> Drop for G<T> {
   |      ^
   |
note: the implementor must specify the same requirement
  --> $DIR/issue-17959.rs:7:1
   |
LL | / struct G<T: ?Sized> {
LL | |     _ptr: *const T
LL | | }
   | |_^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0367`.