    1|       |#![allow(unused_assignments, dead_code)]
    2|       |
    3|       |// compile-flags: --edition=2018 -C opt-level=1
    4|       |
    5|      1|async fn c(x: u8) -> u8 {
    6|      1|    if x == 8 {
    7|      1|        1
    8|       |    } else {
    9|      0|        0
   10|       |    }
   11|      1|}
   12|       |
   13|      0|async fn d() -> u8 { 1 }
   14|       |
   15|      0|async fn e() -> u8 { 1 } // unused function; executor does not block on `g()`
   16|       |
   17|      1|async fn f() -> u8 { 1 }
   18|       |
   19|      0|async fn foo() -> [bool; 10] { [false; 10] } // unused function; executor does not block on `h()`
   20|       |
   21|      1|pub async fn g(x: u8) {
   22|      0|    match x {
   23|      0|        y if e().await == y => (),
   24|      0|        y if f().await == y => (),
   25|      0|        _ => (),
   26|       |    }
   27|      0|}
   28|       |
   29|      1|async fn h(x: usize) { // The function signature is counted when called, but the body is not
   30|      0|                       // executed (not awaited) so the open brace has a `0` count (at least when
   31|      0|                       // displayed with `llvm-cov show` in color-mode).
   32|      0|    match x {
   33|      0|        y if foo().await[y] => (),
   34|      0|        _ => (),
   35|       |    }
   36|      0|}
   37|       |
   38|      1|async fn i(x: u8) { // line coverage is 1, but there are 2 regions:
   39|      1|                    // (a) the function signature, counted when the function is called; and
   40|      1|                    // (b) the open brace for the function body, counted once when the body is
   41|      1|                    // executed asynchronously.
   42|      1|    match x {
   43|      1|        y if c(x).await == y + 1 => { d().await; }
                      ^0       ^0                   ^0 ^0
   44|      1|        y if f().await == y + 1 => (),
                      ^0      ^0                 ^0
   45|      1|        _ => (),
   46|       |    }
   47|      1|}
   48|       |
   49|      1|fn j(x: u8) {
   50|      1|    // non-async versions of `c()`, `d()`, and `f()` to make it similar to async `i()`.
   51|      1|    fn c(x: u8) -> u8 {
   52|      1|        if x == 8 {
   53|      1|            1 // This line appears covered, but the 1-character expression span covering the `1`
                          ^0
   54|      1|              // is not executed. (`llvm-cov show` displays a `^0` below the `1` ). This is because
   55|      1|              // `fn j()` executes the open brace for the function body, followed by the function's
   56|      1|              // first executable statement, `match x`. Inner function declarations are not
   57|      1|              // "visible" to the MIR for `j()`, so the code region counts all lines between the
   58|      1|              // open brace and the first statement as executed, which is, in a sense, true.
   59|      1|              // `llvm-cov show` overcomes this kind of situation by showing the actual counts
   60|      1|              // of the enclosed coverages, (that is, the `1` expression was not executed, and
   61|      1|              // accurately displays a `0`).
   62|      1|        } else {
   63|      1|            0
   64|      1|        }
   65|      1|    }
   66|      1|    fn d() -> u8 { 1 } // inner function is defined in-line, but the function is not executed
                  ^0
   67|      1|    fn f() -> u8 { 1 }
   68|      1|    match x {
   69|      1|        y if c(x) == y + 1 => { d(); }
                      ^0                    ^0
   70|      1|        y if f() == y + 1 => (),
                      ^0                   ^0
   71|      1|        _ => (),
   72|       |    }
   73|      1|}
   74|       |
   75|      0|fn k(x: u8) { // unused function
   76|      0|    match x {
   77|      0|        1 => (),
   78|      0|        2 => (),
   79|      0|        _ => (),
   80|       |    }
   81|      0|}
   82|       |
   83|      1|fn l(x: u8) {
   84|      1|    match x {
   85|      0|        1 => (),
   86|      0|        2 => (),
   87|      1|        _ => (),
   88|       |    }
   89|      1|}
   90|       |
   91|      1|async fn m(x: u8) -> u8 { x - 1 }
                                      ^0
   92|       |
   93|      1|fn main() {
   94|      1|    let _ = g(10);
   95|      1|    let _ = h(9);
   96|      1|    let mut future = Box::pin(i(8));
   97|      1|    j(7);
   98|      1|    l(6);
   99|      1|    let _ = m(5);
  100|      1|    executor::block_on(future.as_mut());
  101|      1|}
  102|       |
  103|       |mod executor {
  104|       |    use core::{
  105|       |        future::Future,
  106|       |        pin::Pin,
  107|       |        task::{Context, Poll, RawWaker, RawWakerVTable, Waker},
  108|       |    };
  109|       |
  110|      1|    pub fn block_on<F: Future>(mut future: F) -> F::Output {
  111|      1|        let mut future = unsafe { Pin::new_unchecked(&mut future) };
  112|      1|        use std::hint::unreachable_unchecked;
  113|      1|        static VTABLE: RawWakerVTable = RawWakerVTable::new(
  114|      1|            |_| unsafe { unreachable_unchecked() }, // clone
                              ^0
  115|      1|            |_| unsafe { unreachable_unchecked() }, // wake
                              ^0
  116|      1|            |_| unsafe { unreachable_unchecked() }, // wake_by_ref
                              ^0
  117|      1|            |_| (),
  118|      1|        );
  119|      1|        let waker = unsafe { Waker::from_raw(RawWaker::new(core::ptr::null(), &VTABLE)) };
  120|      1|        let mut context = Context::from_waker(&waker);
  121|       |
  122|       |        loop {
  123|      1|            if let Poll::Ready(val) = future.as_mut().poll(&mut context) {
  124|      1|                break val;
  125|      0|            }
  126|       |        }
  127|      1|    }
  128|       |}

