From e2ad40debff8fbe9e096d22344359d2238e59042 Mon Sep 17 00:00:00 2001
From: Guillaume Lessard <guillaume.lessard@apple.com>
Date: Mon, 14 Apr 2025 14:52:37 -0700
Subject: [PATCH 1/2] [LifetimeDependenceMutableAccessors] add a long feature
 flag

---
 include/swift/Basic/Features.def |  1 +
 lib/AST/FeatureSet.cpp           | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/swift/Basic/Features.def b/include/swift/Basic/Features.def
index 2bf7ba744f313..6f0d9a42af37e 100644
--- a/include/swift/Basic/Features.def
+++ b/include/swift/Basic/Features.def
@@ -419,6 +419,7 @@ EXPERIMENTAL_FEATURE(LifetimeDependence, true)
 
 /// Enable inout lifetime dependence - @lifetime(&arg)
 EXPERIMENTAL_FEATURE(InoutLifetimeDependence, true)
+EXPERIMENTAL_FEATURE(LifetimeDependenceMutableAccessors, true)
 
 /// Enable the `@_staticExclusiveOnly` attribute.
 EXPERIMENTAL_FEATURE(StaticExclusiveOnly, true)
diff --git a/lib/AST/FeatureSet.cpp b/lib/AST/FeatureSet.cpp
index b17039fa98489..fb39268f3d188 100644
--- a/lib/AST/FeatureSet.cpp
+++ b/lib/AST/FeatureSet.cpp
@@ -293,6 +293,23 @@ static bool usesFeatureInoutLifetimeDependence(Decl *decl) {
   }
 }
 
+static bool usesFeatureLifetimeDependenceMutableAccessors(Decl *decl) {
+  if (!isa<VarDecl>(decl)) {
+    return false;
+  }
+  auto var = cast<VarDecl>(decl);
+  if (!var->isGetterMutating()) {
+    return false;
+  }
+  if (auto dc = var->getDeclContext()) {
+    if (auto nominal = dc->getSelfNominalTypeDecl()) {
+      auto sig = nominal->getGenericSignature();
+      return !var->getInterfaceType()->isEscapable(sig);
+    }
+  }
+  return false;
+}
+
 UNINTERESTING_FEATURE(DynamicActorIsolation)
 UNINTERESTING_FEATURE(NonfrozenEnumExhaustivity)
 UNINTERESTING_FEATURE(ClosureIsolation)

From 3670664ce668d3cf9ebf2af31d6355fc9c664cc7 Mon Sep 17 00:00:00 2001
From: Guillaume Lessard <guillaume.lessard@apple.com>
Date: Mon, 14 Apr 2025 16:57:51 -0700
Subject: [PATCH 2/2] =?UTF-8?q?[stdlib]=20use=20=E2=80=9CLifetimeDependenc?=
 =?UTF-8?q?eMutableAccessors=E2=80=9D?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 stdlib/cmake/modules/SwiftSource.cmake | 1 +
 1 file changed, 1 insertion(+)

diff --git a/stdlib/cmake/modules/SwiftSource.cmake b/stdlib/cmake/modules/SwiftSource.cmake
index b9f45730c5feb..a7893dfec0f73 100644
--- a/stdlib/cmake/modules/SwiftSource.cmake
+++ b/stdlib/cmake/modules/SwiftSource.cmake
@@ -636,6 +636,7 @@ function(_compile_swift_files
   list(APPEND swift_flags "-enable-experimental-feature" "NonescapableTypes")
   list(APPEND swift_flags "-enable-experimental-feature" "LifetimeDependence")
   list(APPEND swift_flags "-enable-experimental-feature" "InoutLifetimeDependence")
+  list(APPEND swift_flags "-enable-experimental-feature" "LifetimeDependenceMutableAccessors")
 
   list(APPEND swift_flags "-enable-upcoming-feature" "MemberImportVisibility")