error[E0128]: type parameters with a default cannot use forward declared identifiers | |
--> $DIR/generic-type-params-forward-mention.rs:2:23 | |
| | |
LL | struct Foo<T = Option<U>, U = bool>(T, U); | |
| ^ defaulted type parameters cannot be forward declared | |
error: aborting due to previous error | |
For more information about this error, try `rustc --explain E0128`. |