| ^^^^^^^^^^ argument requires that `'b` must outlive `'a`
|
= help: consider adding the following bound: `'b: 'a`
+ = note: requirement occurs because of a mutable reference to &isize
+ = note: mutable references are invariant over their type parameter
+ = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
error: higher-ranked subtype error
--> $DIR/region-multiple-lifetime-bounds-on-fns-where-clause.rs:22:12