[Distributed] Generic reqs must be forwarded to accessor from enclosing actor

lib/IRGen/GenDistributed.cpp

@@ -271,9 +271,17 @@ static CanSILFunctionType getAccessorType(IRGenModule &IGM,
     auto *actor = getDistributedActorOf(Target);
     assert(actor);
 
-    for (auto *genericParam : actor->getInnermostGenericParamTypes())
+    for (auto *genericParam : actor->getInnermostGenericParamTypes()) {
       genericParams.push_back(genericParam);
 
+      // and also forward all requirements this generic parameter might have.
+      for (auto req : actor->getGenericRequirements()) {
+        if (req.getFirstType()->isEqual(genericParam)) {
+          genericRequirements.push_back(req);
+        }
+      }
+    }
+
     // Add a generic parameter `D` which stands for decoder type in the
     // accessor signature - `inout D`.
     genericParams.push_back(decoderType);

test/Distributed/Runtime/distributed_actor_generic_constraint_issue_115497090.swift

@@ -0,0 +1,57 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend-emit-module -emit-module-path %t/FakeDistributedActorSystems.swiftmodule -module-name FakeDistributedActorSystems -disable-availability-checking %S/../Inputs/FakeDistributedActorSystems.swift
+// RUN: %target-build-swift -module-name main  -Xfrontend -disable-availability-checking -j2 -parse-as-library -I %t %s %S/../Inputs/FakeDistributedActorSystems.swift -o %t/a.out
+// RUN: %target-run %t/a.out | %FileCheck %s --color
+
+// REQUIRES: executable_test
+// REQUIRES: concurrency
+// REQUIRES: distributed
+
+// rdar://76038845
+// UNSUPPORTED: use_os_stdlib
+// UNSUPPORTED: back_deployment_runtime
+
+import Distributed
+import FakeDistributedActorSystems
+
+import Distributed
+import FakeDistributedActorSystems
+
+typealias DefaultDistributedActorSystem = FakeActorSystem
+
+protocol SomeProtocol {
+  static var isInteger: Bool { get }
+}
+
+distributed actor TestActor<Value> where Value: Codable & Identifiable, Value.ID: SomeProtocol {
+  distributed func requirementsFromActor(value: Value) async throws {
+    print("OK: \(value)")
+  }
+  distributed func requirementsFromActorAndMethod(value: Value) async throws where Value: VerySpecific {
+    print("OK: \(value)")
+  }
+}
+
+protocol VerySpecific {}
+
+struct TheValue: Codable, Identifiable, VerySpecific {
+  let id: String
+  init() {
+    self.id = "id"
+  }
+}
+extension String: SomeProtocol {
+  static var isInteger: Bool { false }
+}
+
+@main struct Main {
+  static func main() async throws {
+    let ta: TestActor<TheValue> = TestActor(actorSystem: .init())
+    try await ta.requirementsFromActor(value: TheValue())
+    try await ta.requirementsFromActorAndMethod(value: TheValue())
+    // CHECK: OK
+  }
+}
+
+// FIXME: repro testing
+// export VER=5.9; swiftly install $VER && swiftly use $VER; swiftly list | grep use; swift build --build-tests; if [[ "$?" -eq 0 ]]; then echo "$VER: OK" >> ../checks; else echo "$VER: broken" >> ../checks; fi