From 42f6596205035ba50520a2c155a921bf386e406f Mon Sep 17 00:00:00 2001
From: Leonard Chan <leonardchan@google.com>
Date: Thu, 27 Aug 2026 20:39:08 +0000
Subject: [PATCH 1/2] compiler: Make +fix-cortex-a53-835769 a default feature
 for aarch64 fuchsia

This matches the default target features for aarch64 fuchsia emitted by
clang.
---
 .../src/spec/targets/aarch64_unknown_fuchsia.rs    |  2 +-
 .../aarch64-fuchsia-target-features.rs             | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 tests/codegen-llvm/aarch64-fuchsia-target-features.rs

diff --git a/compiler/rustc_target/src/spec/targets/aarch64_unknown_fuchsia.rs b/compiler/rustc_target/src/spec/targets/aarch64_unknown_fuchsia.rs
index d16110cfd66f9..8dede888055f7 100644
--- a/compiler/rustc_target/src/spec/targets/aarch64_unknown_fuchsia.rs
+++ b/compiler/rustc_target/src/spec/targets/aarch64_unknown_fuchsia.rs
@@ -5,7 +5,7 @@ use crate::spec::{
 pub(crate) fn target() -> Target {
     let mut base = base::fuchsia::opts();
     base.cpu = "generic".into();
-    base.features = "+v8a,+crc,+aes,+sha2,+neon".into();
+    base.features = "+v8a,+crc,+aes,+sha2,+neon,+fix-cortex-a53-835769".into();
     base.max_atomic_width = Some(128);
     base.stack_probes = StackProbeType::Inline;
     base.supported_sanitizers = SanitizerSet::ADDRESS
diff --git a/tests/codegen-llvm/aarch64-fuchsia-target-features.rs b/tests/codegen-llvm/aarch64-fuchsia-target-features.rs
new file mode 100644
index 0000000000000..32cdc2ce8a553
--- /dev/null
+++ b/tests/codegen-llvm/aarch64-fuchsia-target-features.rs
@@ -0,0 +1,14 @@
+//@ add-minicore
+//@ compile-flags: --crate-type=rlib --target=aarch64-unknown-fuchsia
+//@ needs-llvm-components: aarch64
+
+// CHECK: attributes #0 = { {{.*}}"target-features"="{{.*}}+fix-cortex-a53-835769{{.*}}" }
+
+#![feature(no_core, lang_items)]
+#![no_core]
+
+extern crate minicore;
+use minicore::*;
+
+#[no_mangle]
+pub fn test() {}

From b5e7cbfb9b588982a93a0ec322e26d0dbee8cdc1 Mon Sep 17 00:00:00 2001
From: mehdiakiki <mehdi.akiki@inferal.com>
Date: Mon, 24 Aug 2026 19:27:25 +0100
Subject: [PATCH 2/2] Allow Unpin impls for local extern type

---
 .../src/coherence/builtin.rs                   |  2 ++
 tests/crashes/155053.rs                        | 11 -----------
 .../pin-ergonomics/impl-unpin-extern-type.rs   | 18 ++++++++++++++++++
 3 files changed, 20 insertions(+), 11 deletions(-)
 delete mode 100644 tests/crashes/155053.rs
 create mode 100644 tests/ui/pin-ergonomics/impl-unpin-extern-type.rs

diff --git a/compiler/rustc_hir_analysis/src/coherence/builtin.rs b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
index 34a3f155baf43..f7faefa240abe 100644
--- a/compiler/rustc_hir_analysis/src/coherence/builtin.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
@@ -153,6 +153,8 @@ fn visit_implementation_of_unpin(checker: &Checker<'_>) -> Result<(), ErrorGuara
                 }));
             }
             ty::Adt(_, _) => {}
+            // `extern type`s have no fields, so they can't be structurally pinned.
+            ty::Foreign(_) => {}
             _ => {
                 return Err(tcx.dcx().span_delayed_bug(span, "impl of `Unpin` for a non-adt type"));
             }
diff --git a/tests/crashes/155053.rs b/tests/crashes/155053.rs
deleted file mode 100644
index 31b9ccaf20540..0000000000000
--- a/tests/crashes/155053.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-//@ known-bug: #155053
-#![feature(pin_ergonomics)]
-#![feature(extern_types)]
-
-unsafe extern "C" {
-    type ExternType;
-}
-
-impl Unpin for ExternType {}
-
-fn main() {}
diff --git a/tests/ui/pin-ergonomics/impl-unpin-extern-type.rs b/tests/ui/pin-ergonomics/impl-unpin-extern-type.rs
new file mode 100644
index 0000000000000..953c71ea84311
--- /dev/null
+++ b/tests/ui/pin-ergonomics/impl-unpin-extern-type.rs
@@ -0,0 +1,18 @@
+//! Verify that a local `extern type` can manually implement `Unpin` with `pin_ergonomics` enabled.
+//! Unlike a `#[pin_v2]` ADT, an extern type has no fields that could be structually pinned.
+//!
+//! Regression test for <https://github.com/rust-lang/rust/issues/155053>.
+
+//@ check-pass
+
+#![feature(pin_ergonomics)]
+#![feature(extern_types)]
+#![allow(incomplete_features)]
+
+unsafe extern "C" {
+    type ExternType;
+}
+
+impl Unpin for ExternType {}
+
+fn main() {}