Add remove global actor isolation

Sources/OpenSwiftUICore/Render/GeometryEffect/GeometryEffect.swift

@@ -16,7 +16,7 @@ package import OpenGraphShims
 /// The only change the effect makes to the view's ancestors and descendants is
 /// to change the coordinate transform to and from them.
 @available(OpenSwiftUI_v1_0, *)
-public protocol GeometryEffect: Animatable, ViewModifier where Body == Never {
+public protocol GeometryEffect: Animatable, ViewModifier, _RemoveGlobalActorIsolation where Body == Never {
     /// Returns the current value of the effect.
     func effectValue(size: CGSize) -> ProjectionTransform
 

Sources/OpenSwiftUICore/Util/_RemoveGlobalActor.swift

@@ -0,0 +1,26 @@
+//
+//  _RemoveGlobalActor.swift
+//  OpenSwiftUICore
+//
+//  Audited for 6.5.4
+//  Status: Complete
+//  ID: E36588D6F4797F7C6EF26CC7E1C2D1CE
+
+@globalActor
+public actor _ImpossibleActor: Sendable {
+    public static var shared = _ImpossibleActor()
+
+    public nonisolated var unownedExecutor: UnownedSerialExecutor {
+        _ImpossibleExecutor().asUnownedSerialExecutor()
+    }
+}
+
+private final class _ImpossibleExecutor: SerialExecutor {
+    func enqueue(_ job: consuming ExecutorJob) {
+        preconditionFailure("_RemoveGlobalActorIsolation is not intended to be used as a stand-alone protocol with a global actor isolation.")
+    }
+}
+
+@_marker
+@_ImpossibleActor
+public protocol _RemoveGlobalActorIsolation {}

Tests/OpenSwiftUICoreTests/Util/_RemoveGlobalActorTests.swift

@@ -0,0 +1,33 @@
+//
+//  _RemoveGlobalActorTests.swift
+//  OpenSwiftUICoreTests
+
+import OpenSwiftUICore
+import Testing
+
+// MARK: - _RemoveGlobalActorTests
+
+struct _RemoveGlobalActorTests {
+    @MainActor
+    protocol P {}
+
+    @Test
+    func removeGlobalActorIsolation() {
+        struct A: P, _RemoveGlobalActorIsolation {
+            static func p() {}
+        }
+        A.p()
+    }
+
+    #if compiler(>=6.2)
+    @Test
+    func standaloneConstraintCrash() async {
+        struct B: _RemoveGlobalActorIsolation {
+            static func p() {}
+        }
+        await #expect(processExitsWith: .failure) {
+            await B.p()
+        }
+    }
+    #endif
+}