executor: fix unsoundness due to `impl Trait`, improve macro error handling. (#3425)

* executor-macros: don't parse function bodies.

* executor-macros: refactor for better recovery and ide-friendliness on errors.

* executor-macros: disallow `impl Trait` in task arguments.

Fixes #3420

* Fix example using `impl Trait` in tasks.

1 files changed, 7 insertions, 43 deletions

diff --git a/embassy-executor-macros/src/lib.rs b/embassy-executor-macros/src/lib.rs
index 61d388b9e..5f2182f10 100644
--- a/embassy-executor-macros/src/lib.rs
+++ b/embassy-executor-macros/src/lib.rs
@@ -1,28 +1,11 @@
 #![doc = include_str!("../README.md")]
 extern crate proc_macro;
 
-use darling::ast::NestedMeta;
 use proc_macro::TokenStream;
 
 mod macros;
 mod util;
 use macros::*;
-use syn::parse::{Parse, ParseBuffer};
-use syn::punctuated::Punctuated;
-use syn::Token;
-
-struct Args {
-    meta: Vec<NestedMeta>,
-}
-
-impl Parse for Args {
-    fn parse(input: &ParseBuffer) -> syn::Result<Self> {
-        let meta = Punctuated::<NestedMeta, Token![,]>::parse_terminated(input)?;
-        Ok(Args {
-            meta: meta.into_iter().collect(),
-        })
-    }
-}
 
 /// Declares an async task that can be run by `embassy-executor`. The optional `pool_size` parameter can be used to specify how
 /// many concurrent tasks can be spawned (default is 1) for the function.
@@ -56,17 +39,12 @@ impl Parse for Args {
 /// ```
 #[proc_macro_attribute]
 pub fn task(args: TokenStream, item: TokenStream) -> TokenStream {
-    let args = syn::parse_macro_input!(args as Args);
-    let f = syn::parse_macro_input!(item as syn::ItemFn);
-
-    task::run(&args.meta, f).unwrap_or_else(|x| x).into()
+    task::run(args.into(), item.into()).into()
 }
 
 #[proc_macro_attribute]
 pub fn main_avr(args: TokenStream, item: TokenStream) -> TokenStream {
-    let args = syn::parse_macro_input!(args as Args);
-    let f = syn::parse_macro_input!(item as syn::ItemFn);
-    main::run(&args.meta, f, main::avr()).unwrap_or_else(|x| x).into()
+    main::run(args.into(), item.into(), &main::ARCH_AVR).into()
 }
 
 /// Creates a new `executor` instance and declares an application entry point for Cortex-M spawning the corresponding function body as an async task.
@@ -89,9 +67,7 @@ pub fn main_avr(args: TokenStream, item: TokenStream) -> TokenStream {
 /// ```
 #[proc_macro_attribute]
 pub fn main_cortex_m(args: TokenStream, item: TokenStream) -> TokenStream {
-    let args = syn::parse_macro_input!(args as Args);
-    let f = syn::parse_macro_input!(item as syn::ItemFn);
-    main::run(&args.meta, f, main::cortex_m()).unwrap_or_else(|x| x).into()
+    main::run(args.into(), item.into(), &main::ARCH_CORTEX_M).into()
 }
 
 /// Creates a new `executor` instance and declares an architecture agnostic application entry point spawning
@@ -116,11 +92,7 @@ pub fn main_cortex_m(args: TokenStream, item: TokenStream) -> TokenStream {
 /// ```
 #[proc_macro_attribute]
 pub fn main_spin(args: TokenStream, item: TokenStream) -> TokenStream {
-    let args = syn::parse_macro_input!(args as Args);
-    let f = syn::parse_macro_input!(item as syn::ItemFn);
-    main::run(&args.meta, f, main::spin(&args.meta))
-        .unwrap_or_else(|x| x)
-        .into()
+    main::run(args.into(), item.into(), &main::ARCH_SPIN).into()
 }
 
 /// Creates a new `executor` instance and declares an application entry point for RISC-V spawning the corresponding function body as an async task.
@@ -153,11 +125,7 @@ pub fn main_spin(args: TokenStream, item: TokenStream) -> TokenStream {
 /// ```
 #[proc_macro_attribute]
 pub fn main_riscv(args: TokenStream, item: TokenStream) -> TokenStream {
-    let args = syn::parse_macro_input!(args as Args);
-    let f = syn::parse_macro_input!(item as syn::ItemFn);
-    main::run(&args.meta, f, main::riscv(&args.meta))
-        .unwrap_or_else(|x| x)
-        .into()
+    main::run(args.into(), item.into(), &main::ARCH_RISCV).into()
 }
 
 /// Creates a new `executor` instance and declares an application entry point for STD spawning the corresponding function body as an async task.
@@ -180,9 +148,7 @@ pub fn main_riscv(args: TokenStream, item: TokenStream) -> TokenStream {
 /// ```
 #[proc_macro_attribute]
 pub fn main_std(args: TokenStream, item: TokenStream) -> TokenStream {
-    let args = syn::parse_macro_input!(args as Args);
-    let f = syn::parse_macro_input!(item as syn::ItemFn);
-    main::run(&args.meta, f, main::std()).unwrap_or_else(|x| x).into()
+    main::run(args.into(), item.into(), &main::ARCH_STD).into()
 }
 
 /// Creates a new `executor` instance and declares an application entry point for WASM spawning the corresponding function body as an async task.
@@ -205,7 +171,5 @@ pub fn main_std(args: TokenStream, item: TokenStream) -> TokenStream {
 /// ```
 #[proc_macro_attribute]
 pub fn main_wasm(args: TokenStream, item: TokenStream) -> TokenStream {
-    let args = syn::parse_macro_input!(args as Args);
-    let f = syn::parse_macro_input!(item as syn::ItemFn);
-    main::run(&args.meta, f, main::wasm()).unwrap_or_else(|x| x).into()
+    main::run(args.into(), item.into(), &main::ARCH_WASM).into()
 }