warning: method `foo` is never used
  --> $DIR/coercion-as-explicit-cast.rs:9:8
   |
LL | trait Foo {
   |       --- method in this trait
LL |     fn foo(&self) {}
   |        ^^^
   |
   = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default

warning: 1 warning emitted