tests/ui/match/match-ref-mut-invariance.stderr

   1 error: lifetime may not live long enough
   2   --> $DIR/match-ref-mut-invariance.rs:10:9
   3    |
   4 LL | impl<'b> S<'b> {
   5    |      -- lifetime `'b` defined here
   6 LL |     fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
   7    |            -- lifetime `'a` defined here
   8 LL |         match self.0 { ref mut x => x }
   9    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ associated function was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
  10    |
  11    = help: consider adding the following bound: `'a: 'b`
  12    = note: requirement occurs because of a mutable reference to `&i32`
  13    = note: mutable references are invariant over their type parameter
  14    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
  15
  16 error: aborting due to previous error
  17