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,)*)) })
}
};