nif macro fails with macro arguments

[denumerate]

The nif macro fails when a tuple is passed to a function, like below:

#[rustler::nif]
fn test_fn(item: (usize, usize)) -> (usize, usize) {
    (item.0 + 1, item.1 + 1)
}

The error is:

error: custom attribute panicked
  --> src/lib.rs:37:1
   |
37 | #[rustler::nif]
   | ^^^^^^^^^^^^^^^
   |
   = help: message: unsupported input given: Tuple(TypeTuple { paren_token: Paren, elems: [Path(TypePath { qself: None, path: Path { leading_colon: None, segments: [PathSegment { ident: Ident { ident: "usize", span: #0 bytes(1029..1034) }, arguments: None }] } }), Comma, Path(TypePath { qself: None, path: Path { leading_colon: None, segments: [PathSegment { ident: Ident { ident: "usize", span: #0 bytes(1036..1041) }, arguments: None }] } })] })

I looked into rustler_codegen and it looks like tuple isn't supported in the macro. Is there any special reason for this? Tuples are types provided by the standard library in both rust and elixir, and already have both decode and encode implemented. I could use the NifTuple macro, but I'd probably just be re-implementing tuples, which seems wasteful.

[filmor]

It should be enough to add a syn::Type::Tuple branch to this match https://github.com/rusterlium/rustler/blob/master/rustler_codegen/src/nif.rs#L118

The decoder already exists, so you can probably just use the exact same implementation as https://github.com/rusterlium/rustler/blob/master/rustler_codegen/src/nif.rs#L119-L128

[denumerate]

Thanks for the help! That at least worked locally