Parse_Str does not return a correct error

[Bleachfuel]

why does parse_str not return the span at which it failed? Or does it do that and am I missing something, because I'm having trouble highlighting the spans at which parsing fails.

        if let Some(lit) = literal {
            syn::parse_str::<syn::WherePredicate>(&lit.value())
            .map(Some)
            .map_err(|err| {
                syn::Error::new_spanned(lit, err)
            })
        } else {
            Ok(None)
        }