error[E0107]: missing generics for associated type `MapLike::VRefCont`
  --> $DIR/issue-79422.rs:45:36
   |
LL |         as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
   |                                    ^^^^^^^^ expected 1 lifetime argument
   |
note: associated type defined here, with 1 lifetime parameter: `'a`
  --> $DIR/issue-79422.rs:18:10
   |
LL |     type VRefCont<'a>: RefCont<'a, V>
   |          ^^^^^^^^ --
help: add missing lifetime argument
   |
LL |         as Box<dyn MapLike<u8, u8, VRefCont<'a> = dyn RefCont<'_, u8>>>;
   |                                            ++++

error[E0038]: the trait `MapLike` is not dyn compatible
  --> $DIR/issue-79422.rs:45:20
   |
LL |         as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` 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-79422.rs:18:10
   |
LL | trait MapLike<K, V> {
   |       ------- this trait is not dyn compatible...
LL |     type VRefCont<'a>: RefCont<'a, V>
   |          ^^^^^^^^ ...because it contains the generic associated type `VRefCont`
   = help: consider moving `VRefCont` to another trait

error: aborting due to 2 previous errors

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