1 files changed, 193 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/redundant_async_block.rs b/src/tools/clippy/tests/ui/redundant_async_block.rs
new file mode 100644
index 000000000..7ae235583
--- /dev/null
+++ b/src/tools/clippy/tests/ui/redundant_async_block.rs
@@ -0,0 +1,193 @@
+// run-rustfix
+
+#![allow(unused, clippy::manual_async_fn)]
+#![warn(clippy::redundant_async_block)]
+
+use std::future::Future;
+
+async fn func1(n: usize) -> usize {
+    n + 1
+}
+
+async fn func2() -> String {
+    let s = String::from("some string");
+    let f = async { (*s).to_owned() };
+    let x = async { f.await };
+    x.await
+}
+
+fn main() {
+    let fut1 = async { 17 };
+    // Lint
+    let fut2 = async { fut1.await };
+
+    let fut1 = async { 25 };
+    // Lint
+    let fut2 = async move { fut1.await };
+
+    // Lint
+    let fut = async { async { 42 }.await };
+
+    // Do not lint: not a single expression
+    let fut = async {
+        func1(10).await;
+        func2().await
+    };
+
+    // Do not lint: expression contains `.await`
+    let fut = async { func1(func2().await.len()).await };
+}
+
+#[allow(clippy::let_and_return)]
+fn capture_local() -> impl Future<Output = i32> {
+    let fut = async { 17 };
+    // Lint
+    async move { fut.await }
+}
+
+fn capture_local_closure(s: &str) -> impl Future<Output = &str> {
+    let f = move || std::future::ready(s);
+    // Do not lint: `f` would not live long enough
+    async move { f().await }
+}
+
+#[allow(clippy::let_and_return)]
+fn capture_arg(s: &str) -> impl Future<Output = &str> {
+    let fut = async move { s };
+    // Lint
+    async move { fut.await }
+}
+
+fn capture_future_arg<T>(f: impl Future<Output = T>) -> impl Future<Output = T> {
+    // Lint
+    async { f.await }
+}
+
+fn capture_func_result<FN, F, T>(f: FN) -> impl Future<Output = T>
+where
+    F: Future<Output = T>,
+    FN: FnOnce() -> F,
+{
+    // Do not lint, as f() would be evaluated prematurely
+    async { f().await }
+}
+
+fn double_future(f: impl Future<Output = impl Future<Output = u32>>) -> impl Future<Output = u32> {
+    // Do not lint, we will get a `.await` outside a `.async`
+    async { f.await.await }
+}
+
+fn await_in_async<F, R>(f: F) -> impl Future<Output = u32>
+where
+    F: FnOnce() -> R,
+    R: Future<Output = u32>,
+{
+    // Lint
+    async { async { f().await + 1 }.await }
+}
+
+#[derive(Debug, Clone)]
+struct F {}
+
+impl F {
+    async fn run(&self) {}
+}
+
+pub async fn run() {
+    let f = F {};
+    let c = f.clone();
+    // Do not lint: `c` would not live long enough
+    spawn(async move { c.run().await });
+    let _f = f;
+}
+
+fn spawn<F: Future + 'static>(_: F) {}
+
+async fn work(_: &str) {}
+
+fn capture() {
+    let val = "Hello World".to_owned();
+    // Do not lint: `val` would not live long enough
+    spawn(async { work(&{ val }).await });
+}
+
+fn await_from_macro() -> impl Future<Output = u32> {
+    macro_rules! mac {
+        ($e:expr) => {
+            $e.await
+        };
+    }
+    // Do not lint: the macro may change in the future
+    // or return different things depending on its argument
+    async { mac!(async { 42 }) }
+}
+
+fn async_expr_from_macro() -> impl Future<Output = u32> {
+    macro_rules! mac {
+        () => {
+            async { 42 }
+        };
+    }
+    // Do not lint: the macro may change in the future
+    async { mac!().await }
+}
+
+fn async_expr_from_macro_deep() -> impl Future<Output = u32> {
+    macro_rules! mac {
+        () => {
+            async { 42 }
+        };
+    }
+    // Do not lint: the macro may change in the future
+    async { ({ mac!() }).await }
+}
+
+fn all_from_macro() -> impl Future<Output = u32> {
+    macro_rules! mac {
+        () => {
+            // Lint
+            async { async { 42 }.await }
+        };
+    }
+    mac!()
+}
+
+fn parts_from_macro() -> impl Future<Output = u32> {
+    macro_rules! mac {
+        ($e: expr) => {
+            // Do not lint: `$e` might not always be side-effect free
+            async { $e.await }
+        };
+    }
+    mac!(async { 42 })
+}
+
+fn safe_parts_from_macro() -> impl Future<Output = u32> {
+    macro_rules! mac {
+        ($e: expr) => {
+            // Lint
+            async { async { $e }.await }
+        };
+    }
+    mac!(42)
+}
+
+fn parts_from_macro_deep() -> impl Future<Output = u32> {
+    macro_rules! mac {
+        ($e: expr) => {
+            // Do not lint: `$e` might not always be side-effect free
+            async { ($e,).0.await }
+        };
+    }
+    let f = std::future::ready(42);
+    mac!(f)
+}
+
+fn await_from_macro_deep() -> impl Future<Output = u32> {
+    macro_rules! mac {
+        ($e:expr) => {{ $e }.await};
+    }
+    // Do not lint: the macro may change in the future
+    // or return different things depending on its argument
+    async { mac!(async { 42 }) }
+}