From 92a5d21bc4a0b735750a4dff1eac204ce636b513 Mon Sep 17 00:00:00 2001
From: Eric Holk <ericholk@microsoft.com>
Date: Thu, 19 Sep 2024 15:29:01 -0700
Subject: [PATCH] Add a test case to make sure we don't reborrow twice

---
 tests/ui/async-await/pin-reborrow-arg.rs      |  2 +-
 tests/ui/async-await/pin-reborrow-once.rs     | 13 +++++++++++++
 tests/ui/async-await/pin-reborrow-once.stderr | 12 ++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/async-await/pin-reborrow-once.rs
 create mode 100644 tests/ui/async-await/pin-reborrow-once.stderr

diff --git a/tests/ui/async-await/pin-reborrow-arg.rs b/tests/ui/async-await/pin-reborrow-arg.rs
index 34f23533b65..b3e8718d036 100644
--- a/tests/ui/async-await/pin-reborrow-arg.rs
+++ b/tests/ui/async-await/pin-reborrow-arg.rs
@@ -15,7 +15,7 @@ fn baz(self: Pin<&mut Self>) {
 fn foo(_: Pin<&mut Foo>) {
 }
 
-fn bar(mut x: Pin<&mut Foo>) {
+fn bar(x: Pin<&mut Foo>) {
     foo(x);
     foo(x); // for this to work we need to automatically reborrow,
             // as if the user had written `foo(x.as_mut())`.
diff --git a/tests/ui/async-await/pin-reborrow-once.rs b/tests/ui/async-await/pin-reborrow-once.rs
new file mode 100644
index 00000000000..241efadef7d
--- /dev/null
+++ b/tests/ui/async-await/pin-reborrow-once.rs
@@ -0,0 +1,13 @@
+#![feature(pin_ergonomics)]
+#![allow(dead_code, incomplete_features)]
+
+// Make sure with pin reborrowing that we can only get one mutable reborrow of a pinned reference.
+
+use std::pin::{pin, Pin};
+
+fn twice(_: Pin<&mut i32>, _: Pin<&mut i32>) {}
+
+fn main() {
+    let x = pin!(42);
+    twice(x, x); //~ ERROR cannot borrow
+}
diff --git a/tests/ui/async-await/pin-reborrow-once.stderr b/tests/ui/async-await/pin-reborrow-once.stderr
new file mode 100644
index 00000000000..b8fde8ffee8
--- /dev/null
+++ b/tests/ui/async-await/pin-reborrow-once.stderr
@@ -0,0 +1,12 @@
+error[E0499]: cannot borrow `*x.__pointer` as mutable more than once at a time
+  --> $DIR/pin-reborrow-once.rs:12:14
+   |
+LL |     twice(x, x);
+   |     ----- -  ^ second mutable borrow occurs here
+   |     |     |
+   |     |     first mutable borrow occurs here
+   |     first borrow later used by call
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0499`.