Cannot add field that's not Arc<...>

[Nashenas88]

Currently it's not possible to add a field that's not Arc<...>. This makes sense for fields that are #[inject], but fields that are not #[inject] are also rejected, which should not occur.

The following is rejected, when it should not be:

#[derive(Inject)]
#[provides(Struct with Struct::new())]
struct Struct {
    a: usize,
}

impl Struct {
    fn new() -> Self {
        Self { a: 0 }
    }
}