1 #![feature(trait_alias)] // Enabled to reduce stderr output, but can be triggered even if disabled. 2 trait Trait {} 3 trait WithType { 4 type Ctx; 5 } 6 trait Alias<T> = where T: Trait; 7 8 impl<T> WithType for T { 9 type Ctx = dyn Alias<T>; 10 //~^ ERROR at least one trait is required for an object type [E0224] 11 } main()12fn main() {} 13