rtic-macros: wrap everything in macro_rules! to improve the error experience and

royally **** up the DX experience (for lib.rs in rtic-macros, at least :P)

rtic-macros/src/codegen/bindings.rs

@@ -1,10 +1,3 @@
-#[cfg(not(any(
-    feature = "cortex-m-source-masking",
-    feature = "cortex-m-basepri",
-    feature = "test-template"
-)))]
-compile_error!("No backend selected");
-
 #[cfg(any(feature = "cortex-m-source-masking", feature = "cortex-m-basepri"))]
 pub use cortex::*;
 

rtic-macros/src/lib.rs

@@ -4,35 +4,50 @@
 )]
 //deny_warnings_placeholder_for_ci
 
-use proc_macro::TokenStream;
-use std::{env, fs, path::Path};
+macro_rules! with_backend {
+    (mod: [$($mod:tt),*]) => {
+        $(
+            with_backend!{ mod $mod; }
+        )*
+    };
+    ($($tokens:tt)*) => {
+        #[cfg(any(
+            feature = "cortex-m-source-masking",
+            feature = "cortex-m-basepri",
+            feature = "test-template"
+        ))]
+        $($tokens)*
+    };
+}
 
-mod analyze;
-mod check;
-mod codegen;
-mod syntax;
+with_backend! { mod: [analyze, check, codegen, syntax] }
+with_backend! { use std::{fs, env, path::Path}; }
+with_backend! { use proc_macro::TokenStream; }
 
-// Used for mocking the API in testing
-#[doc(hidden)]
-#[proc_macro_attribute]
-pub fn mock_app(args: TokenStream, input: TokenStream) -> TokenStream {
+with_backend! {
+    // Used for mocking the API in testing
+    #[doc(hidden)]
+    #[proc_macro_attribute]
+    pub fn mock_app(args: TokenStream, input: TokenStream) -> TokenStream {
         if let Err(e) = syntax::parse(args, input) {
             e.to_compile_error().into()
         } else {
             "fn main() {}".parse().unwrap()
         }
+    }
 }
 
-/// Attribute used to declare a RTIC application
-///
-/// For user documentation see the [RTIC book](https://rtic.rs)
-///
-/// # Panics
-///
-/// Should never panic, cargo feeds a path which is later converted to a string
-#[proc_macro_attribute]
-pub fn app(args: TokenStream, input: TokenStream) -> TokenStream {
-    let (app, analysis) = match syntax::parse(args, input) {
+with_backend! {
+    /// Attribute used to declare a RTIC application
+    ///
+    /// For user documentation see the [RTIC book](https://rtic.rs)
+    ///
+    /// # Panics
+    ///
+    /// Should never panic, cargo feeds a path which is later converted to a string
+    #[proc_macro_attribute]
+    pub fn app(_args: TokenStream, _input: TokenStream) -> TokenStream {
+        let (app, analysis) = match syntax::parse(_args, _input) {
             Err(e) => return e.to_compile_error().into(),
             Ok(x) => x,
         };
@@ -87,4 +102,12 @@ pub fn app(args: TokenStream, input: TokenStream) -> TokenStream {
         }
 
         ts.into()
+    }
 }
+
+#[cfg(not(any(
+    feature = "cortex-m-source-masking",
+    feature = "cortex-m-basepri",
+    feature = "test-template"
+)))]
+compile_error!("Cannot compile. No backend feature selected.");