fixup! refactor(embassy): Allow building net without a backend for do…

…cs and linting

src/riot-rs-embassy/src/lib.rs

@@ -77,7 +77,7 @@ cfg_if::cfg_if! {
     } else if #[cfg(context = "riot-rs")] {
         compile_error!("no backend for net is active");
     } else {
-        type NetworkDevice = network::DummyDriver;
+        use network::DummyDriver as NetworkDevice;
     }
 }
 
@@ -271,9 +271,6 @@ async fn init_task(mut peripherals: arch::OptionalPeripherals) {
     #[cfg(feature = "wifi-esp")]
     let device = arch::wifi::esp_wifi::init(&mut peripherals, spawner);
 
-    #[cfg(not(any(feature = "wifi-esp", feature = "wifi-cyw43", feature = "usb-ethernet")))]
-    let device = panic!();
-
     #[cfg(feature = "net")]
     {
         use embassy_net::StackResources;
@@ -286,6 +283,12 @@ async fn init_task(mut peripherals: arch::OptionalPeripherals) {
             "maximum number of concurrent sockets allowed by the network stack"
         );
 
+        #[cfg(not(any(feature = "wifi-esp", feature = "wifi-cyw43", feature = "usb-ethernet")))]
+        // The creation of `device` is not organized in such a way that they could be put in a
+        // cfg-if without larger refactoring; relying on unused variable lints to keep the
+        // condition list up to date.
+        let device: NetworkDevice = network::new_dummy();
+
         let config = network::config();
 
         // Generate random seed

src/riot-rs-embassy/src/network.rs

@@ -21,6 +21,7 @@ pub(crate) async fn net_task(mut runner: Runner<'static, NetworkDevice>) -> ! {
     runner.run().await
 }
 
+#[allow(dead_code, reason = "false positive during builds outside of laze")]
 pub(crate) fn config() -> embassy_net::Config {
     #[cfg(not(feature = "override-network-config"))]
     {
@@ -35,12 +36,26 @@ pub(crate) fn config() -> embassy_net::Config {
     }
 }
 
-/// An uninhabited type that stands in for a network driver in documentation and linting.
+/// Constructor for [`DummyDriver`']
+///
+/// This is a standalone function instead of an associated method to ease moving [`DummyDriver`]
+/// into [`embassy_net`].
+#[allow(
+    dead_code,
+    reason = "constructor is only used in linter / documentation situations"
+)]
+pub(crate) fn new_dummy() -> DummyDriver {
+    panic!(
+        "DummyDriver must only ever be constructed for documentation and linting, not for running"
+    )
+}
+
+/// Stand-in for a network driver in documentation and linting.
 ///
 /// It also doubles as the infallible type for its own associated types.
 // FIXME: This should be core::convert::Infallible as soon as embassy-net implements the traits on
 // that.
-pub(crate) enum DummyDriver {}
+pub(crate) struct DummyDriver(core::convert::Infallible);
 
 impl embassy_net::driver::Driver for DummyDriver {
     type RxToken<'a> = Self
@@ -55,23 +70,23 @@ impl embassy_net::driver::Driver for DummyDriver {
         &mut self,
         _cx: &mut core::task::Context,
     ) -> Option<(Self::RxToken<'_>, Self::TxToken<'_>)> {
-        match *self {}
+        match self.0 {}
     }
 
     fn transmit(&mut self, _cx: &mut core::task::Context) -> Option<Self::TxToken<'_>> {
-        match *self {}
+        match self.0 {}
     }
 
     fn link_state(&mut self, _cx: &mut core::task::Context) -> embassy_net::driver::LinkState {
-        match *self {}
+        match self.0 {}
     }
 
     fn capabilities(&self) -> embassy_net::driver::Capabilities {
-        match *self {}
+        match self.0 {}
     }
 
     fn hardware_address(&self) -> embassy_net::driver::HardwareAddress {
-        match *self {}
+        match self.0 {}
     }
 }
 
@@ -80,7 +95,7 @@ impl embassy_net::driver::TxToken for DummyDriver {
     where
         F: FnOnce(&mut [u8]) -> R,
     {
-        match self {}
+        match self.0 {}
     }
 }
 
@@ -89,6 +104,6 @@ impl embassy_net::driver::RxToken for DummyDriver {
     where
         F: FnOnce(&mut [u8]) -> R,
     {
-        match self {}
+        match self.0 {}
     }
 }