error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
  --> $DIR/issue-67535.rs:3:1
   |
LL | impl std::ops::AddAssign for () {
   | ^^^^^-------------------^^^^^--
   | |    |                       |
   | |    |                       this is not defined in the current crate because tuples are always foreign
   | |    this is not defined in the current crate because this is a foreign trait
   | impl doesn't use only types from inside the current crate
   |
   = note: define and implement a trait or new type instead

error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
  --> $DIR/issue-67535.rs:10:1
   |
LL | impl std::ops::AddAssign for [(); 1] {
   | ^^^^^-------------------^^^^^-------
   | |    |                       |
   | |    |                       this is not defined in the current crate because arrays are always foreign
   | |    this is not defined in the current crate because this is a foreign trait
   | impl doesn't use only types from inside the current crate
   |
   = note: define and implement a trait or new type instead

error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
  --> $DIR/issue-67535.rs:17:1
   |
LL | impl std::ops::AddAssign for &[u8] {
   | ^^^^^-------------------^^^^^-----
   | |    |                       |
   | |    |                       this is not defined in the current crate because slices are always foreign
   | |    this is not defined in the current crate because this is a foreign trait
   | impl doesn't use only types from inside the current crate
   |
   = note: define and implement a trait or new type instead

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0117`.