error: expected one of `>`, a const expression, lifetime, or type, found `,` --> $DIR/issue-20616-7.rs:28:22 | LL | type Type_7 = Box<(),,>; | ^ expected one of `>`, a const expression, lifetime, or type | help: you might have meant to end the type parameters here | LL | type Type_7 = Box<()>,,>; | + error: aborting due to 1 previous error