From 96d917992ca591def3d7be87bc9f03486549b2a0 Mon Sep 17 00:00:00 2001 From: Dario Nieuwenhuis <dirbaio@dirbaio.net> Date: Tue, 26 Apr 2022 18:36:38 +0200 Subject: [PATCH] macros: simplify task macro using "TAIT laundering". --- embassy-macros/src/macros/task.rs | 31 ++++++++++++++----------------- 1 file changed, 14 insertions(+), 17 deletions(-) diff --git a/embassy-macros/src/macros/task.rs b/embassy-macros/src/macros/task.rs index c37ad212c..396ce18f2 100644 --- a/embassy-macros/src/macros/task.rs +++ b/embassy-macros/src/macros/task.rs @@ -33,12 +33,10 @@ pub fn run(args: syn::AttributeArgs, f: syn::ItemFn) -> Result<TokenStream, Toke ctxt.error_spanned_by(&f.sig, "pool_size must be 1 or greater"); } - let mut arg_types = Vec::new(); let mut arg_names = Vec::new(); - let mut arg_indexes = Vec::new(); let mut fargs = f.sig.inputs.clone(); - for (i, arg) in fargs.iter_mut().enumerate() { + for arg in fargs.iter_mut() { match arg { syn::FnArg::Receiver(_) => { ctxt.error_spanned_by(arg, "task functions must not have receiver arguments"); @@ -46,8 +44,6 @@ pub fn run(args: syn::AttributeArgs, f: syn::ItemFn) -> Result<TokenStream, Toke syn::FnArg::Typed(t) => match t.pat.as_mut() { syn::Pat::Ident(id) => { arg_names.push(id.ident.clone()); - arg_types.push(t.ty.clone()); - arg_indexes.push(syn::Index::from(i)); id.mutability = None; } _ => { @@ -64,8 +60,6 @@ pub fn run(args: syn::AttributeArgs, f: syn::ItemFn) -> Result<TokenStream, Toke let task_ident = f.sig.ident.clone(); let task_inner_ident = format_ident!("__{}_task", task_ident); - let mod_ident = format_ident!("__{}_mod", task_ident); - let args_ident = format_ident!("__{}_args", task_ident); let mut task_inner = f; let visibility = task_inner.vis.clone(); @@ -73,29 +67,32 @@ pub fn run(args: syn::AttributeArgs, f: syn::ItemFn) -> Result<TokenStream, Toke task_inner.sig.ident = task_inner_ident.clone(); let result = quote! { + // This is the user's task function, renamed. + // We put it outside the #task_ident fn below, because otherwise + // the items defined there (such as POOL) would be in scope + // in the user's code. #task_inner - #[allow(non_camel_case_types)] - type #args_ident = (#(#arg_types,)*); - - mod #mod_ident { + #visibility fn #task_ident(#fargs) -> #embassy_path::executor::SpawnToken<impl ::core::future::Future + 'static> { + use ::core::future::Future; use #embassy_path::executor::SpawnToken; use #embassy_path::executor::raw::TaskStorage; - type Fut = impl ::core::future::Future + 'static; + type Fut = impl Future + 'static; #[allow(clippy::declare_interior_mutable_const)] const NEW_TS: TaskStorage<Fut> = TaskStorage::new(); static POOL: [TaskStorage<Fut>; #pool_size] = [NEW_TS; #pool_size]; - pub(super) fn task(args: super::#args_ident) -> SpawnToken<Fut> { - unsafe { TaskStorage::spawn_pool(&POOL, move || super::#task_inner_ident(#(args.#arg_indexes),*)) } + // Opaque type laundering, to obscure its origin! + // Workaround for "opaque type's hidden type cannot be another opaque type from the same scope" + // https://github.com/rust-lang/rust/issues/96406 + fn launder_tait(token: SpawnToken<impl Future+'static>) -> SpawnToken<impl Future+'static> { + token } - } - #visibility fn #task_ident(#fargs) -> #embassy_path::executor::SpawnToken<impl ::core::future::Future + 'static> { - #mod_ident::task((#(#arg_names,)*)) + launder_tait(unsafe { TaskStorage::spawn_pool(&POOL, move || #task_inner_ident(#(#arg_names,)*)) }) } };