1 error[E0425]: cannot find value `o` in this scope
2 --> $DIR/trailing-question-in-macro-type.rs:12:15
4 LL | fn_expr!{ o?.when(|&i| i > 0)?.when(|&i| i%2 == 0) };
5 | ^ not found in this scope
7 error: aborting due to previous error
9 For more information about this error, try `rustc --explain E0425`.