From 6d988dc1e307db8e04442a75a757f6aeb7b3c2c9 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Wed, 28 Apr 2021 08:47:09 -0700
Subject: [PATCH] Fix undocumented unsafe in AssertUnwindSafe impls

---
 library/core/src/panic/unwind_safe.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/library/core/src/panic/unwind_safe.rs b/library/core/src/panic/unwind_safe.rs
index c889dd81846..a1ee47e4d48 100644
--- a/library/core/src/panic/unwind_safe.rs
+++ b/library/core/src/panic/unwind_safe.rs
@@ -281,6 +281,7 @@ impl<F: Future> Future for AssertUnwindSafe<F> {
     type Output = F::Output;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        // SAFETY: pin projection. AssertUnwindSafe follows structural pinning.
         let pinned_field = unsafe { Pin::map_unchecked_mut(self, |x| &mut x.0) };
         F::poll(pinned_field, cx)
     }
@@ -291,6 +292,7 @@ impl<S: Stream> Stream for AssertUnwindSafe<S> {
     type Item = S::Item;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<S::Item>> {
+        // SAFETY: pin projection. AssertUnwindSafe follows structural pinning.
         unsafe { self.map_unchecked_mut(|x| &mut x.0) }.poll_next(cx)
     }