[Distributed] Improve getting return type metadata for distributed invocations

rdar://141313340

Author: ktoso

stdlib/public/runtime/MetadataLookup.cpp

@@ -2945,8 +2945,13 @@ swift_func_getReturnTypeInfo(const char *typeNameStart, size_t typeNameLength,
 
   SubstGenericParametersFromMetadata substFn(genericEnv, genericArguments);
 
-  DecodedMetadataBuilder builder(
-      demangler,
+  auto request = MetadataRequest(MetadataState::Complete,
+      /*non-blocking*/ true);
+
+  NodePointer nodePointer = resultType->getFirstChild();
+  auto typeInfoOrErr = swift_getTypeByMangledNode(
+      request, demangler, nodePointer,
+      /*arguments=*/{},
       /*substGenericParam=*/
       [&substFn](unsigned depth, unsigned index) {
         return substFn.getMetadata(depth, index).Ptr;
@@ -2956,9 +2961,12 @@ swift_func_getReturnTypeInfo(const char *typeNameStart, size_t typeNameLength,
         return substFn.getWitnessTable(type, index);
       });
 
-  TypeDecoder<DecodedMetadataBuilder> decoder(builder);
+  if (typeInfoOrErr.isError()) {
+    return nullptr;
+  }
 
-  return decodeType(decoder, resultType->getFirstChild());
+  auto typeInfo = typeInfoOrErr.getType();
+  return typeInfo.getMetadata();
 }
 
 SWIFT_CC(swift) SWIFT_RUNTIME_STDLIB_SPI

test/Distributed/Inputs/FakeDistributedActorSystems.swift

@@ -459,7 +459,7 @@ public final class FakeInvocationDecoder: DistributedTargetInvocationDecoder {
 
   var argumentIndex: Int = 0
 
-  fileprivate init(
+  public init(
     args: [Any],
     substitutions: [Any.Type] = [],
     returnType: Any.Type? = nil,

test/Distributed/Runtime/distributed_actor_func_calls_without_touching_returnType_metadata_first.swift

@@ -0,0 +1,76 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend-emit-module -emit-module-path %t/FakeDistributedActorSystems.swiftmodule -module-name FakeDistributedActorSystems -target %target-swift-5.7-abi-triple %S/../Inputs/FakeDistributedActorSystems.swift
+// RUN: %target-build-swift -module-name main -target %target-swift-5.7-abi-triple -j2 -parse-as-library -plugin-path %swift-plugin-dir -I %t %s %S/../Inputs/FakeDistributedActorSystems.swift -o %t/a.out
+// RUN: %target-codesign %t/a.out
+// RUN: %target-run %t/a.out | %FileCheck %s
+
+// REQUIRES: executable_test
+// REQUIRES: concurrency
+// REQUIRES: distributed
+
+// rdar://76038845
+// UNSUPPORTED: use_os_stdlib
+// UNSUPPORTED: back_deployment_runtime
+
+// FIXME(distributed): Distributed actors currently have some issues on windows, isRemote always returns false. rdar://82593574
+// UNSUPPORTED: OS=windows-msvc
+
+import Distributed
+import FakeDistributedActorSystems
+
+typealias DefaultDistributedActorSystem = FakeRoundtripActorSystem
+
+struct SuperLargeSizeStruct: Codable {
+  let i1a: Int = 0
+  let i2a: Int = 0
+  let i3a: Int = 0
+  let i4a: Int = 0
+  let i5a: Int = 0
+  let i6a: Int = 0
+  let i7a: Int = 0
+  let i8a: Int = 0
+}
+
+@available(SwiftStdlib 6.0, *)
+distributed actor TheWorker {
+  typealias ActorSystem = DefaultDistributedActorSystem
+
+  distributed func callMeCallMe() async throws -> SuperLargeSizeStruct {
+    return .init()
+  }
+}
+
+@available(SwiftStdlib 6.0, *)
+func test_generic(system: DefaultDistributedActorSystem) async throws {
+  let localW = TheWorker(actorSystem: system)
+  let remoteW = try! TheWorker.resolve(id: localW.id, using: system)
+
+  let target = RemoteCallTarget("$s4main9TheWorkerC010callMeCallE0AA20SuperLargeSizeStructVyYaKFTE")
+  var invocation = FakeInvocationEncoder()
+  try invocation.recordReturnType(SuperLargeSizeStruct.self)
+  try invocation.recordErrorType(Error.self)
+  try invocation.doneRecording()
+
+  do {
+    try await system.remoteCall(
+      on: localW,
+      target: target,
+      invocation: &invocation,
+      throwing: Error.self,
+      returning: SuperLargeSizeStruct.self
+    )
+    // CHECK: >> remoteCall: on:main.TheWorker, target:main.TheWorker.callMeCallMe(), invocation:FakeInvocationEncoder(genericSubs: [], arguments: [], returnType: Optional(main.SuperLargeSizeStruct), errorType: Optional(Swift.Error)), throwing:Swift.Error, returning:main.SuperLargeSizeStruct
+    // CHECK: > execute distributed target: main.TheWorker.callMeCallMe(), identifier: $s4main9TheWorkerC010callMeCallE0AA20SuperLargeSizeStructVyYaKFTE
+    // CHECK: << remoteCall return: SuperLargeSizeStruct
+  }
+  print("==== ----------------------------------------------------------------")
+}
+
+@available(SwiftStdlib 6.0, *)
+@main struct Main {
+  static func main() async {
+    let system = DefaultDistributedActorSystem()
+    print("===================================================================")
+    try! await test_generic(system: system)
+  }
+}