1 error[E0596]: cannot borrow `foo` as mutable, as it is not declared as mutable
2 --> $DIR/span-covering-argument-1.rs:5:14
5 | ^^^^^^^ cannot borrow as mutable
7 LL | bad!(foo whatever);
8 | ------------------ in this macro invocation
10 = note: this error originates in the macro `bad` (in Nightly builds, run with -Z macro-backtrace for more info)
11 help: consider changing this to be mutable
16 error: aborting due to previous error
18 For more information about this error, try `rustc --explain E0596`.