run cargo bless

tests/ui/async_yields_async.fixed

@@ -1,5 +1,5 @@
 #![warn(clippy::async_yields_async)]
-#![allow(clippy::redundant_async_block)]
+#![allow(clippy::redundant_async_block, clippy::missing_must_use_on_future_types)]
 
 use core::future::Future;
 use core::pin::Pin;

tests/ui/async_yields_async.rs

@@ -1,5 +1,5 @@
 #![warn(clippy::async_yields_async)]
-#![allow(clippy::redundant_async_block)]
+#![allow(clippy::redundant_async_block, clippy::missing_must_use_on_future_types)]
 
 use core::future::Future;
 use core::pin::Pin;

tests/ui/crashes/ice-13862.rs

@@ -1,5 +1,6 @@
 #![crate_type = "lib"]
 #![no_std]
+#![allow(clippy::missing_must_use_on_future_types)]
 
 use core::future::Future;
 use core::pin::Pin;

tests/ui/missing_must_use_on_future_types.fixed

@@ -0,0 +1,118 @@
+#![warn(clippy::missing_must_use_on_future_types)]
+#![allow(path_statements, unused, clippy::no_effect)]
+
+use std::fmt::Display;
+use std::future::Future;
+use std::marker::PhantomData;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+// basic struct case
+#[must_use]
+struct BasicStruct;
+
+impl Future for BasicStruct {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+// basic enum case
+#[must_use]
+enum BasicEnum {
+    Var1,
+    Var2,
+}
+
+impl Future for BasicEnum {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+// should be ignored if type doesn't implement `Future`
+struct NonFuture;
+
+// should still trigger if a type only sometimes implements `Future`
+#[must_use]
+struct SometimesFuture<T>(PhantomData<T>);
+
+impl<T: Copy> Future for SometimesFuture<T> {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+// should be ignored on trait objects
+trait Trait {}
+
+impl Future for dyn Trait {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+struct TraitImpl {}
+impl Trait for TraitImpl {}
+
+fn trait_obj() -> Box<dyn Trait> {
+    Box::new(TraitImpl {})
+}
+
+// struct with multiple fields and impls
+#[derive(Debug)]
+#[must_use]
+pub struct ComplexStruct {
+    x: usize,
+    y: &'static str,
+}
+
+impl ComplexStruct {
+    fn sum(&self) -> usize {
+        self.x + self.y.len()
+    }
+}
+
+impl Display for ComplexStruct {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "complex")
+    }
+}
+
+impl Future for ComplexStruct {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+// should be ignored on already #[must_use] struct
+#[must_use]
+struct AlreadyMustUse;
+
+impl Future for AlreadyMustUse {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+fn main() {
+    BasicStruct;
+    BasicEnum::Var2;
+    NonFuture;
+    SometimesFuture::<String>(PhantomData);
+    trait_obj();
+    ComplexStruct { x: 42, y: "complex" };
+    AlreadyMustUse;
+}

tests/ui/missing_must_use_on_future_types.stderr

@@ -0,0 +1,52 @@
+error: this struct implements `Future` but is missing a `#[must_use]` attribute
+  --> tests/ui/missing_must_use_on_future_types.rs:11:1
+   |
+LL | struct BasicStruct;
+   | ^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::missing-must-use-on-future-types` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::missing_must_use_on_future_types)]`
+help: add the attribute
+   |
+LL + #[must_use]
+LL | struct BasicStruct;
+   |
+
+error: this struct implements `Future` but is missing a `#[must_use]` attribute
+  --> tests/ui/missing_must_use_on_future_types.rs:22:1
+   |
+LL | enum BasicEnum {
+   | ^^^^^^^^^^^^^^
+   |
+help: add the attribute
+   |
+LL + #[must_use]
+LL | enum BasicEnum {
+   |
+
+error: this struct implements `Future` but is missing a `#[must_use]` attribute
+  --> tests/ui/missing_must_use_on_future_types.rs:39:1
+   |
+LL | struct SometimesFuture<T>(PhantomData<T>);
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add the attribute
+   |
+LL + #[must_use]
+LL | struct SometimesFuture<T>(PhantomData<T>);
+   |
+
+error: this struct implements `Future` but is missing a `#[must_use]` attribute
+  --> tests/ui/missing_must_use_on_future_types.rs:69:1
+   |
+LL | pub struct ComplexStruct {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add the attribute
+   |
+LL + #[must_use]
+LL | pub struct ComplexStruct {
+   |
+
+error: aborting due to 4 previous errors
+