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macros: simplify task macro using "TAIT laundering".

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This commit is contained in:
Dario Nieuwenhuis 2022-04-26 18:36:38 +02:00
parent a39d796c3d
commit 96d917992c
1 changed files with 14 additions and 17 deletions
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31
embassy-macros/src/macros/task.rs
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@ -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,)*)) })
}
};