Bug: "Item is not monomorphic" for `--monomorphize`

[ssyram]

Code snippet to reproduce the bug:

trait Modifiable<T> {
    fn modify(&mut self, arg: &T) -> T;
}
impl <T : Clone> Modifiable<T> for i32 {
    fn modify(&mut self, arg: &T) -> T {
        *self += 1;
        arg.clone()
    }
}
fn modify_something<T: Clone>(arg: &T) -> T {
    let x = &mut 199;
    x.modify(arg)
}
fn main() {
    let y = &mut 99;
    assert!(!modify_something(&"Hello, world!".to_string()).is_empty());
    assert_eq!(y.modify(&mut 100), 100);
}

Reproduction of error:

Then, we simply run:

charon rustc --monomorphize -- charon/tests/ui/mono.rs

Bug Report: Then we get the bug:

note: the error occurred when translating `core::fmt::{impl core::fmt::Display::<Str>}::fmt`, which is (transitively) used at the following location(s):
  --> charon/tests/ui/mono.rs:16:32
   |
16 |     assert!(!modify_something(&"Hello, world!".to_string()).is_empty());
   |                                ---------------------------
warning: Item is not monomorphic: Mono(ItemRef { contents: Node { id: Id { id: 1104 }, value: ItemRefContents { def_id: core::fmt::Formatter, generic_args: [Lifetime(Region { kind: ReBound(0, BoundRegion { var: 2, kind: Anon }) })], impl_exprs: [], in_trait: None, has_param: true } } })

[N1ark]

Smaller reproduction:

fn main() {
    let a = "Hello, world!".to_string();
}

[Nadrieril]

Tried it again just now, this got fixed in the meantime :)