error[E0366]: Implementations of Drop cannot be specialized
  --> $DIR/issue-38868.rs:5:1
   |
LL | / impl Drop for List<i32> {
LL | |     fn drop(&mut self) {
LL | |         panic!()
LL | |     }
LL | | }
   | |_^
   |
note: Use same sequence of generic type and region parameters that is on the struct/enum definition
  --> $DIR/issue-38868.rs:1:1
   |
LL | / pub struct List<T> {
LL | |     head: T,
LL | | }
   | |_^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0366`.