error[E0107]: missing generics for associated type `SuperTrait::SubType`
  --> $DIR/issue-76535.rs:39:33
   |
LL |     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
   |                                 ^^^^^^^ expected 1 lifetime argument
   |
note: associated type defined here, with 1 lifetime parameter: `'a`
  --> $DIR/issue-76535.rs:9:10
   |
LL |     type SubType<'a>: SubTrait where Self: 'a;
   |          ^^^^^^^ --
help: add missing lifetime argument
   |
LL |     let sub: Box<dyn SuperTrait<SubType<'a> = SubStruct>> = Box::new(SuperStruct::new(0));
   |                                        ++++

error: aborting due to previous error

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