error[E0038]: the trait `Bar` is not dyn compatible
  --> $DIR/mention-correct-dyn-incompatible-trait.rs:19:24
   |
LL |     let test: &mut dyn Bar = &mut thing;
   |                        ^^^ `Bar` 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/mention-correct-dyn-incompatible-trait.rs:4:8
   |
LL |     fn foo<T>(&self, val: T);
   |        ^^^ ...because method `foo` has generic type parameters
...
LL | trait Bar: Foo { }
   |       --- this trait is not dyn compatible...
   = help: consider moving `foo` to another trait
   = help: only type `Thing` implements `Bar`; consider using it directly instead.

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0038`.