warning: method `foo_a` is never used
  --> $DIR/replace-vptr.rs:4:8
   |
LL | trait A {
   |       - method in this trait
LL |     fn foo_a(&self);
   |        ^^^^^
   |
   = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default

warning: method `foo_c` is never used
  --> $DIR/replace-vptr.rs:12:8
   |
LL | trait C: A + B {
   |       - method in this trait
LL |     fn foo_c(&self);
   |        ^^^^^

warning: 2 warnings emitted