error[E0107]: missing generics for associated type `C::DType`
  --> $DIR/issue-81712-cyclic-traits.rs:14:10
   |
LL |     type DType<T>: D<T, CType = Self>;
   |          ^^^^^ expected 1 type argument
   |
note: associated type defined here, with 1 type parameter: `T`
  --> $DIR/issue-81712-cyclic-traits.rs:14:10
   |
LL |     type DType<T>: D<T, CType = Self>;
   |          ^^^^^ -
help: use angle brackets to add missing type argument
   |
LL |     type DType<T><T>: D<T, CType = Self>;
   |               ^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0107`.