#[constructor]Expand description
A dummy macro that does nothing.
This exists so #[uniffi::export] can emit its input verbatim without
causing unexpected errors, plus some extra code in case everything is okay.
It is important for #[uniffi::export] to not raise unexpected errors if it
fails to parse the input as this happens very often when the proc-macro is
run on an incomplete input by rust-analyzer while the developer is typing.