error[E0596]: cannot borrow `foo` as mutable, as it is not declared as mutable --> $DIR/span-covering-argument-1.rs:5:14 | LL | *&mut $s = 0; | ^^^^^^^ cannot borrow as mutable ... LL | bad!(foo whatever); | ------------------ in this macro invocation | = note: this error originates in the macro `bad` (in Nightly builds, run with -Z macro-backtrace for more info) help: consider changing this to be mutable | LL | let mut $s = 0; | +++ error: aborting due to previous error For more information about this error, try `rustc --explain E0596`.