error[E0617]: can't pass a function item to a variadic function
  --> $DIR/issue-32201.rs:9:16
   |
LL |         foo(0, bar);
   |                ^^^
   |
   = help: a function item is zero-sized and needs to be cast into a function pointer to be used in FFI
   = note: for more information on function items, visit https://doc.rust-lang.org/reference/types/function-item.html
help: use a function pointer instead
   |
LL |         foo(0, bar as fn(*const u8));
   |                    ++++++++++++++++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0617`.