From 3e655665b76e5771d74b6b2af9de1eaef5f43b60 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sat, 19 Sep 2020 11:33:16 +0200
Subject: [PATCH 1/2] test VecDeque::iter_mut aliasing

---
 tests/run-pass/vecdeque.rs | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/tests/run-pass/vecdeque.rs b/tests/run-pass/vecdeque.rs
index 9c9909802e..34f32ee1d9 100644
--- a/tests/run-pass/vecdeque.rs
+++ b/tests/run-pass/vecdeque.rs
@@ -1,5 +1,17 @@
 use std::collections::VecDeque;
 
+fn test_all_refs<'a, T: 'a>(dummy: &mut T, iter: impl Iterator<Item = &'a mut T>) {
+    // Gather all those references.
+    let mut refs: Vec<&mut T> = iter.collect();
+    // Use them all. Twice, to be sure we got all interleavings.
+    for r in refs.iter_mut() {
+        std::mem::swap(dummy, r);
+    }
+    for r in refs {
+        std::mem::swap(dummy, r);
+    }
+}
+
 fn main() {
     let mut dst = VecDeque::new();
     dst.push_front(Box::new(1));
@@ -18,6 +30,21 @@ fn main() {
     println!("{:?}", VecDeque::<u32>::new().iter());
 
     for a in dst {
-      assert_eq!(*a, 2);
+        assert_eq!(*a, 2);
     }
+
+    // # Aliasing tests.
+    let mut v = std::collections::VecDeque::new();
+    v.push_back(1);
+    v.push_back(2);
+
+    // Test `fold` bad aliasing.
+    let mut it = v.iter_mut();
+    let ref0 = it.next().unwrap();
+    let sum = it.fold(0, |x, y| x + *y);
+    assert_eq!(*ref0 + sum, 3);
+
+    // Test general iterator aliasing.
+    v.push_front(0);
+    test_all_refs(&mut 0, v.iter_mut());
 }

From 63a0f04ed05af0b0822bfe000511e37489b71662 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Wed, 7 Oct 2020 09:05:18 +0200
Subject: [PATCH 2/2] rustup; bring back mir-opt-level 3

---
 ci.sh        | 3 +--
 rust-version | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/ci.sh b/ci.sh
index a6daa80645..56a6f1228a 100755
--- a/ci.sh
+++ b/ci.sh
@@ -25,8 +25,7 @@ function run_tests {
   ./miri test --locked
   if ! [ -n "${MIRI_TEST_TARGET+exists}" ]; then
     # Only for host architecture: tests with MIR optimizations
-    #FIXME: Only testing opt level 1 due to <https://github.com/rust-lang/rust/issues/77564>.
-    MIRIFLAGS="-Z mir-opt-level=1" ./miri test --locked
+    MIRIFLAGS="-Z mir-opt-level=3" ./miri test --locked
   fi
   # "miri test" has built the sysroot for us, now this should pass without
   # any interactive questions.
diff --git a/rust-version b/rust-version
index b0644a3d73..79ba8eebc1 100644
--- a/rust-version
+++ b/rust-version
@@ -1 +1 @@
-efbaa413061c2a6e52f06f00a60ee7830fcf3ea5
+c9ced8523bbb90561385aab305232f2167228a83