1 error: expected one of `>`, identifier, lifetime, or type, found `,`
2 --> $DIR/issue-20616-3.rs:25:24
4 LL | type Type_3<T> = Box<T,,>; //~ error: expected one of `>`, identifier, lifetime, or type, found `,`
5 | ^ expected one of `>`, identifier, lifetime, or type here
7 error: aborting due to previous error