error[E0107]: missing generics for associated type `SuperTrait::SubType`
  --> $DIR/issue-76535.rs:34:33
   |
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:4:10
   |
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[E0038]: the trait `SuperTrait` is not dyn compatible
  --> $DIR/issue-76535.rs:34:22
   |
LL |     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` is not dyn compatible
   |
note: for a trait to be dyn compatible it needs to allow building a vtable
      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
  --> $DIR/issue-76535.rs:4:10
   |
LL | pub trait SuperTrait {
   |           ---------- this trait is not dyn compatible...
LL |     type SubType<'a>: SubTrait where Self: 'a;
   |          ^^^^^^^ ...because it contains the generic associated type `SubType`
   = help: consider moving `SubType` to another trait
   = help: only type `SuperStruct` implements `SuperTrait` within this crate; consider using it directly instead.
   = note: `SuperTrait` may be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0038, E0107.
For more information about an error, try `rustc --explain E0038`.