src/lib.rs:206:14: 206:54 error: type mismatch: the type `fn(&mut syntax::ext::base::ExtCtxt<'_>, syntax::codemap::Span, &syntax::codemap::Spanned<syntax::ast::MetaItem_>, syntax::ext::base::Annotatable) -> syntax::ext::base::Annotatable {packet_modifier}` implements the trait `for<'r, 'r, 'r> core::ops::Fn<(&'r mut syntax::ext::base::ExtCtxt<'r>, syntax::codemap::Span, &'r syntax::codemap::Spanned<syntax::ast::MetaItem_>, syntax::ext::base::Annotatable)>`, but the trait `for<'r, 'r, 'r, 'r, 'r> core::ops::Fn<(&'r mut syntax::ext::base::ExtCtxt<'r>, syntax::codemap::Span, &'r syntax::codemap::Spanned<syntax::ast::MetaItem_>, &'r syntax::ext::base::Annotatable, &'r mut core::ops::FnMut(syntax::ext::base::Annotatable) + 'r)>` is required (expected a tuple with 5 elements, found one with 4 elements) [E0281]