From ba2f14e065ef4a798b23fad8b786616e79c59dd5 Mon Sep 17 00:00:00 2001
From: Chase Wilson <me@chasewilson.dev>
Date: Sat, 4 Jun 2022 12:33:01 -0500
Subject: [PATCH 1/3] Fixed premature assertions that caused -Z
 randomize-layout to fail on alloc

---
 compiler/rustc_codegen_ssa/src/base.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 420adec456f6..ecb7863304d6 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -216,11 +216,12 @@ pub fn unsize_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
             let mut result = None;
             for i in 0..src_layout.fields.count() {
                 let src_f = src_layout.field(bx.cx(), i);
-                assert_eq!(src_layout.fields.offset(i).bytes(), 0);
-                assert_eq!(dst_layout.fields.offset(i).bytes(), 0);
                 if src_f.is_zst() {
                     continue;
                 }
+
+                assert_eq!(src_layout.fields.offset(i).bytes(), 0);
+                assert_eq!(dst_layout.fields.offset(i).bytes(), 0);
                 assert_eq!(src_layout.size, src_f.size);
 
                 let dst_f = dst_layout.field(bx.cx(), i);

From 857453d36c5b396d2009e08b38b672695c5cddba Mon Sep 17 00:00:00 2001
From: Chase Wilson <me@chasewilson.dev>
Date: Sat, 4 Jun 2022 13:33:56 -0500
Subject: [PATCH 2/3] Added test for #97732

---
 src/test/ui/unsized/issue-97732.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 src/test/ui/unsized/issue-97732.rs

diff --git a/src/test/ui/unsized/issue-97732.rs b/src/test/ui/unsized/issue-97732.rs
new file mode 100644
index 000000000000..172f0724d426
--- /dev/null
+++ b/src/test/ui/unsized/issue-97732.rs
@@ -0,0 +1,23 @@
+// check-pass
+
+#![feature(coerce_unsized)]
+
+// Ensure that unsizing structs that contain ZSTs at non-zero offsets don't ICE
+
+use std::ops::CoerceUnsized;
+
+#[repr(C)]
+pub struct BoxWithZstTail<T: ?Sized>(Box<T>, ());
+
+impl<S: ?Sized, T: ?Sized> CoerceUnsized<BoxWithZstTail<T>> for BoxWithZstTail<S> where
+    Box<S>: CoerceUnsized<Box<T>>
+{
+}
+
+pub fn noop_dyn_upcast_with_zst_tail(
+    b: BoxWithZstTail<dyn Send + Sync>,
+) -> BoxWithZstTail<dyn Send> {
+    b
+}
+
+fn main() {}

From 10336cf1624ada36e8ba64e851d4df3f2976da81 Mon Sep 17 00:00:00 2001
From: Chase Wilson <buckshot1233@gmail.com>
Date: Mon, 6 Jun 2022 10:19:33 -0500
Subject: [PATCH 3/3] Update src/test/ui/unsized/issue-97732.rs

Co-authored-by: Eduard-Mihai Burtescu <edy.burt@gmail.com>
---
 src/test/ui/unsized/issue-97732.rs | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/test/ui/unsized/issue-97732.rs b/src/test/ui/unsized/issue-97732.rs
index 172f0724d426..72f765033969 100644
--- a/src/test/ui/unsized/issue-97732.rs
+++ b/src/test/ui/unsized/issue-97732.rs
@@ -15,9 +15,14 @@ impl<S: ?Sized, T: ?Sized> CoerceUnsized<BoxWithZstTail<T>> for BoxWithZstTail<S
 }
 
 pub fn noop_dyn_upcast_with_zst_tail(
-    b: BoxWithZstTail<dyn Send + Sync>,
-) -> BoxWithZstTail<dyn Send> {
+    b: BoxWithZstTail<dyn ToString + Send>,
+) -> BoxWithZstTail<dyn ToString> {
     b
 }
 
-fn main() {}
+fn main() {
+    let original = "foo";
+    let boxed = BoxWithZstTail(Box::new(original) as Box<dyn ToString + Send>, ());
+    let noop_upcasted = noop_dyn_upcast_with_zst_tail(boxed);
+    assert_eq!(original, noop_upcasted.0.to_string());
+}