foo.sh

set -ex
rm -rf tmp
mkdir tmp

rustc="rustc --out-dir tmp -L tmp -C debuginfo=2"
$rustc mycore.rs --crate-type rlib
$rustc mystd.rs --crate-type dylib -C prefer-dynamic
$rustc mygetopts.rs --crate-type rlib
$rustc mytest.rs --crate-type dylib -C prefer-dynamic

mycore.rs

pub trait Object { fn method(&self) { } }

impl Object for u32 { }
impl Object for () { }
impl<T> Object for &T { }

pub fn unused() {
    let ref u = 0_u32;
    let _d = &u as &dyn crate::Object;
    loop { }
}

mygetopts.rs

extern crate mystd;
use mystd::Object;

pub fn another_dyn_debug() {
    let ref u = 1_u32;
    let _d = &u as &dyn crate::Object;
    loop { }
}

mystd.rs

extern crate mycore;
pub use mycore::Object;

mytest.rs

extern crate mygetopts;