error: return types are denoted using `->`
  --> $DIR/avoid-ice-on-warning.rs:4:23
   |
LL | fn call_this<F>(f: F) : Fn(&str) + call_that {}
   |                       ^
   |
help: use `->` instead
   |
LL | fn call_this<F>(f: F) -> Fn(&str) + call_that {}
   |                       ~~

error[E0405]: cannot find trait `call_that` in this scope
  --> $DIR/avoid-ice-on-warning.rs:4:36
   |
LL | fn call_this<F>(f: F) : Fn(&str) + call_that {}
   |                                    ^^^^^^^^^ not found in this scope

warning: trait objects without an explicit `dyn` are deprecated
  --> $DIR/avoid-ice-on-warning.rs:4:25
   |
LL | fn call_this<F>(f: F) : Fn(&str) + call_that {}
   |                         ^^^^^^^^^^^^^^^^^^^^
   |
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
   = note: `#[warn(bare_trait_objects)]` on by default
help: if this is an object-safe trait, use `dyn`
   |
LL | fn call_this<F>(f: F) : dyn Fn(&str) + call_that {}
   |                         +++

error: aborting due to 2 previous errors; 1 warning emitted

For more information about this error, try `rustc --explain E0405`.