error: expected one of `>`, a const expression, lifetime, or type, found `,` --> $DIR/issue-20616-3.rs:13:24 | LL | type Type_3 = Box; | ^ expected one of `>`, a const expression, lifetime, or type | help: you might have meant to end the type parameters here | LL | type Type_3 = Box,,>; | + error: aborting due to previous error