1 files changed, 128 insertions, 0 deletions
diff --git a/tests/run-make/coverage/async.rs b/tests/run-make/coverage/async.rs
new file mode 100644
index 00000000000..efd9e62d64e
--- /dev/null
+++ b/tests/run-make/coverage/async.rs
@@ -0,0 +1,128 @@
+#![allow(unused_assignments, dead_code)]
+
+// compile-flags: --edition=2018 -C opt-level=1
+
+async fn c(x: u8) -> u8 {
+    if x == 8 {
+        1
+    } else {
+        0
+    }
+}
+
+async fn d() -> u8 { 1 }
+
+async fn e() -> u8 { 1 } // unused function; executor does not block on `g()`
+
+async fn f() -> u8 { 1 }
+
+async fn foo() -> [bool; 10] { [false; 10] } // unused function; executor does not block on `h()`
+
+pub async fn g(x: u8) {
+    match x {
+        y if e().await == y => (),
+        y if f().await == y => (),
+        _ => (),
+    }
+}
+
+async fn h(x: usize) { // The function signature is counted when called, but the body is not
+                       // executed (not awaited) so the open brace has a `0` count (at least when
+                       // displayed with `llvm-cov show` in color-mode).
+    match x {
+        y if foo().await[y] => (),
+        _ => (),
+    }
+}
+
+async fn i(x: u8) { // line coverage is 1, but there are 2 regions:
+                    // (a) the function signature, counted when the function is called; and
+                    // (b) the open brace for the function body, counted once when the body is
+                    // executed asynchronously.
+    match x {
+        y if c(x).await == y + 1 => { d().await; }
+        y if f().await == y + 1 => (),
+        _ => (),
+    }
+}
+
+fn j(x: u8) {
+    // non-async versions of `c()`, `d()`, and `f()` to make it similar to async `i()`.
+    fn c(x: u8) -> u8 {
+        if x == 8 {
+            1 // This line appears covered, but the 1-character expression span covering the `1`
+              // is not executed. (`llvm-cov show` displays a `^0` below the `1` ). This is because
+              // `fn j()` executes the open brace for the function body, followed by the function's
+              // first executable statement, `match x`. Inner function declarations are not
+              // "visible" to the MIR for `j()`, so the code region counts all lines between the
+              // open brace and the first statement as executed, which is, in a sense, true.
+              // `llvm-cov show` overcomes this kind of situation by showing the actual counts
+              // of the enclosed coverages, (that is, the `1` expression was not executed, and
+              // accurately displays a `0`).
+        } else {
+            0
+        }
+    }
+    fn d() -> u8 { 1 } // inner function is defined in-line, but the function is not executed
+    fn f() -> u8 { 1 }
+    match x {
+        y if c(x) == y + 1 => { d(); }
+        y if f() == y + 1 => (),
+        _ => (),
+    }
+}
+
+fn k(x: u8) { // unused function
+    match x {
+        1 => (),
+        2 => (),
+        _ => (),
+    }
+}
+
+fn l(x: u8) {
+    match x {
+        1 => (),
+        2 => (),
+        _ => (),
+    }
+}
+
+async fn m(x: u8) -> u8 { x - 1 }
+
+fn main() {
+    let _ = g(10);
+    let _ = h(9);
+    let mut future = Box::pin(i(8));
+    j(7);
+    l(6);
+    let _ = m(5);
+    executor::block_on(future.as_mut());
+}
+
+mod executor {
+    use core::{
+        future::Future,
+        pin::Pin,
+        task::{Context, Poll, RawWaker, RawWakerVTable, Waker},
+    };
+
+    pub fn block_on<F: Future>(mut future: F) -> F::Output {
+        let mut future = unsafe { Pin::new_unchecked(&mut future) };
+        use std::hint::unreachable_unchecked;
+        static VTABLE: RawWakerVTable = RawWakerVTable::new(
+            |_| unsafe { unreachable_unchecked() }, // clone
+            |_| unsafe { unreachable_unchecked() }, // wake
+            |_| unsafe { unreachable_unchecked() }, // wake_by_ref
+            |_| (),
+        );
+        let waker = unsafe { Waker::from_raw(RawWaker::new(core::ptr::null(), &VTABLE)) };
+        let mut context = Context::from_waker(&waker);
+
+        loop {
+            if let Poll::Ready(val) = future.as_mut().poll(&mut context) {
+                break val;
+            }
+        }
+    }
+}