error[E0381]: used binding `y` is possibly-uninitialized
  --> $DIR/no-non-guaranteed-initialization.rs:9:5
   |
LL |     let y;
   |         - binding declared here but left uninitialized
LL |     if x > 5 {
   |        ----- if this `if` condition is `false`, `y` is not initialized
LL |         y = echo(10).await;
LL |     }
   |      - an `else` arm might be missing here, initializing `y`
LL |     y
   |     ^ `y` used here but it is possibly-uninitialized

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0381`.