Merge #1236

1236: Add `#[must_use]` to all futures r=Dirbaio a=GrantM11235

I think that's all of them, I just grep'd for `impl.* Future for`

Co-authored-by: Grant Miller <GrantM11235@gmail.com>

embassy-futures/src/yield_now.rs

@@ -24,6 +24,7 @@ pub fn yield_now() -> impl Future<Output = ()> {
     YieldNowFuture { yielded: false }
 }
 
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 struct YieldNowFuture {
     yielded: bool,
 }

embassy-nrf/src/gpiote.rs

@@ -315,6 +315,7 @@ impl<'d, C: Channel, T: GpioPin> OutputChannel<'d, C, T> {
 
 // =======================
 
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub(crate) struct PortInputFuture<'a> {
     pin: PeripheralRef<'a, AnyPin>,
 }

embassy-rp/src/dma.rs

@@ -151,6 +151,7 @@ fn copy_inner<'a, C: Channel>(
     Transfer::new(ch)
 }
 
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct Transfer<'a, C: Channel> {
     channel: PeripheralRef<'a, C>,
 }

embassy-rp/src/gpio.rs

@@ -193,6 +193,7 @@ unsafe fn IO_IRQ_BANK0() {
     }
 }
 
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 struct InputFuture<'a, T: Pin> {
     pin: PeripheralRef<'a, T>,
     level: InterruptTrigger,

embassy-rp/src/pio.rs

@@ -120,6 +120,7 @@ unsafe fn PIO1_IRQ_0() {
 }
 
 /// Future that waits for TX-FIFO to become writable
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct FifoOutFuture<'a, PIO: PioInstance, SM: PioStateMachine + Unpin> {
     sm: &'a mut SM,
     pio: PhantomData<PIO>,
@@ -182,6 +183,7 @@ impl<'d, PIO: PioInstance, SM: PioStateMachine + Unpin> Drop for FifoOutFuture<'
 }
 
 /// Future that waits for RX-FIFO to become readable
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct FifoInFuture<'a, PIO: PioInstance, SM: PioStateMachine> {
     sm: &'a mut SM,
     pio: PhantomData<PIO>,
@@ -241,6 +243,7 @@ impl<'d, PIO: PioInstance, SM: PioStateMachine> Drop for FifoInFuture<'d, PIO, S
 }
 
 /// Future that waits for IRQ
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct IrqFuture<PIO: PioInstance> {
     pio: PhantomData<PIO>,
     irq_no: u8,

embassy-stm32/src/dma/mod.rs

@@ -273,6 +273,7 @@ mod transfers {
         Transfer::new(channel)
     }
 
+    #[must_use = "futures do nothing unless you `.await` or poll them"]
     pub(crate) struct Transfer<'a, C: Channel> {
         channel: PeripheralRef<'a, C>,
     }

embassy-stm32/src/exti.rs

@@ -198,6 +198,7 @@ mod eha {
     }
 }
 
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 struct ExtiInputFuture<'a> {
     pin: u8,
     phantom: PhantomData<&'a mut AnyPin>,

embassy-sync/src/channel.rs

@@ -181,6 +181,7 @@ where
 }
 
 /// Future returned by [`Channel::recv`] and  [`Receiver::recv`].
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct RecvFuture<'ch, M, T, const N: usize>
 where
     M: RawMutex,
@@ -203,6 +204,7 @@ where
 }
 
 /// Future returned by [`DynamicReceiver::recv`].
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct DynamicRecvFuture<'ch, T> {
     channel: &'ch dyn DynamicChannel<T>,
 }
@@ -219,6 +221,7 @@ impl<'ch, T> Future for DynamicRecvFuture<'ch, T> {
 }
 
 /// Future returned by [`Channel::send`] and  [`Sender::send`].
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct SendFuture<'ch, M, T, const N: usize>
 where
     M: RawMutex,
@@ -250,6 +253,7 @@ where
 impl<'ch, M, T, const N: usize> Unpin for SendFuture<'ch, M, T, N> where M: RawMutex {}
 
 /// Future returned by [`DynamicSender::send`].
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct DynamicSendFuture<'ch, T> {
     channel: &'ch dyn DynamicChannel<T>,
     message: Option<T>,

embassy-sync/src/pipe.rs

@@ -48,6 +48,7 @@ where
 }
 
 /// Future returned by [`Pipe::write`] and  [`Writer::write`].
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct WriteFuture<'p, M, const N: usize>
 where
     M: RawMutex,
@@ -110,6 +111,7 @@ where
 }
 
 /// Future returned by [`Pipe::read`] and  [`Reader::read`].
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct ReadFuture<'p, M, const N: usize>
 where
     M: RawMutex,

embassy-time/src/timer.rs

@@ -26,6 +26,7 @@ pub async fn with_timeout<F: Future>(timeout: Duration, fut: F) -> Result<F::Out
 }
 
 /// A future that completes at a specified [Instant](struct.Instant.html).
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct Timer {
     expires_at: Instant,
     yielded_once: bool,