diff --git a/include/swift/AST/TypeCheckRequests.h b/include/swift/AST/TypeCheckRequests.h
index 88434b3103a18..7349a21aa9dbd 100644
--- a/include/swift/AST/TypeCheckRequests.h
+++ b/include/swift/AST/TypeCheckRequests.h
@@ -2693,9 +2693,13 @@ enum class CustomAttrTypeKind {
   /// any contextual type parameters.
   NonGeneric,
 
-  /// Property delegates have some funky rules, like allowing
+  /// Property wrappers have some funky rules, like allowing
   /// unbound generic types.
-  PropertyDelegate,
+  PropertyWrapper,
+
+  /// Global actors are represented as custom type attributes. They don't
+  /// have any particularly interesting semantics.
+  GlobalActor,
 };
 
 void simple_display(llvm::raw_ostream &out, CustomAttrTypeKind value);
diff --git a/lib/AST/TypeCheckRequests.cpp b/lib/AST/TypeCheckRequests.cpp
index b72542686e9c4..214a1473f87e5 100644
--- a/lib/AST/TypeCheckRequests.cpp
+++ b/lib/AST/TypeCheckRequests.cpp
@@ -1427,8 +1427,12 @@ void swift::simple_display(llvm::raw_ostream &out, CustomAttrTypeKind value) {
     out << "non-generic";
     return;
 
-  case CustomAttrTypeKind::PropertyDelegate:
-    out << "property-delegate";
+  case CustomAttrTypeKind::PropertyWrapper:
+    out << "property-wrapper";
+    return;
+
+  case CustomAttrTypeKind::GlobalActor:
+    out << "global-actor";
     return;
   }
   llvm_unreachable("bad kind");
diff --git a/lib/Sema/TypeCheckConcurrency.cpp b/lib/Sema/TypeCheckConcurrency.cpp
index 474512979861c..28ba235fb2542 100644
--- a/lib/Sema/TypeCheckConcurrency.cpp
+++ b/lib/Sema/TypeCheckConcurrency.cpp
@@ -25,6 +25,24 @@
 
 using namespace swift;
 
+/// Determine whether it makes sense to infer an attribute in the given
+/// context.
+static bool shouldInferAttributeInContext(const DeclContext *dc) {
+  auto sourceFile = dc->getParentSourceFile();
+  if (!sourceFile)
+    return false;
+
+  switch (sourceFile->Kind) {
+  case SourceFileKind::Interface:
+  case SourceFileKind::SIL:
+    return false;
+
+  case SourceFileKind::Library:
+  case SourceFileKind::Main:
+    return true;
+  }
+}
+
 /// Check whether the @asyncHandler attribute can be applied to the given
 /// function declaration.
 ///
@@ -108,7 +126,7 @@ bool IsAsyncHandlerRequest::evaluate(
     return true;
   }
 
-  if (!func->getASTContext().LangOpts.EnableExperimentalConcurrency)
+  if (!shouldInferAttributeInContext(func->getDeclContext()))
     return false;
 
   // Are we in a context where inference is possible?
@@ -1013,15 +1031,18 @@ static Optional<ActorIsolation> getIsolationFromAttributes(Decl *decl) {
   // If the declaration is marked with a global actor, report it as being
   // part of that global actor.
   if (globalActorAttr) {
-    TypeResolutionOptions options(TypeResolverContext::None);
-    TypeResolution resolver = TypeResolution::forInterface(
-        decl->getInnermostDeclContext(), options, nullptr);
-    Type globalActorType = resolver.resolveType(
-        globalActorAttr->first->getTypeRepr(), nullptr);
+    ASTContext &ctx = decl->getASTContext();
+    auto dc = decl->getInnermostDeclContext();
+    Type globalActorType = evaluateOrDefault(
+        ctx.evaluator,
+        CustomAttrTypeRequest{
+          globalActorAttr->first, dc, CustomAttrTypeKind::GlobalActor},
+        Type());
     if (!globalActorType || globalActorType->hasError())
       return ActorIsolation::forUnspecified();
 
-    return ActorIsolation::forGlobalActor(globalActorType);
+    return ActorIsolation::forGlobalActor(
+        globalActorType->mapTypeOutOfContext());
   }
 
   llvm_unreachable("Forgot about an attribute?");
@@ -1135,23 +1156,32 @@ ActorIsolation ActorIsolationRequest::evaluate(
   }
 
   // Disable inference of actor attributes outside of normal Swift source files.
-  if (auto sourceFile = value->getDeclContext()->getParentSourceFile()) {
-    switch (sourceFile->Kind) {
-    case SourceFileKind::Interface:
-    case SourceFileKind::SIL:
-      return defaultIsolation;
-
-    case SourceFileKind::Library:
-    case SourceFileKind::Main:
-      // Attempt inference below.
-      break;
-    }
-  } else {
+  if (!shouldInferAttributeInContext(value->getDeclContext()))
     return defaultIsolation;
-  }
 
   // Function used when returning an inferred isolation.
   auto inferredIsolation = [&](ActorIsolation inferred) {
+    // Add an implicit attribute to capture the actor isolation that was
+    // inferred, so that (e.g.) it will be printed and serialized.
+    ASTContext &ctx = value->getASTContext();
+    switch (inferred) {
+    case ActorIsolation::Independent:
+      value->getAttrs().add(new (ctx) ActorIndependentAttr(true));
+      break;
+
+    case ActorIsolation::GlobalActor: {
+      auto typeExpr = TypeExpr::createImplicit(inferred.getGlobalActor(), ctx);
+      auto attr = CustomAttr::create(
+          ctx, SourceLoc(), typeExpr, /*implicit=*/true);
+      value->getAttrs().add(attr);
+      break;
+    }
+
+    case ActorIsolation::ActorInstance:
+    case ActorIsolation::Unspecified:
+      // Nothing to do.
+      break;
+    }
     return inferred;
   };
 
diff --git a/lib/Sema/TypeCheckPropertyWrapper.cpp b/lib/Sema/TypeCheckPropertyWrapper.cpp
index 14f18c8a4f412..9529b61d06270 100644
--- a/lib/Sema/TypeCheckPropertyWrapper.cpp
+++ b/lib/Sema/TypeCheckPropertyWrapper.cpp
@@ -513,7 +513,7 @@ Type AttachedPropertyWrapperTypeRequest::evaluate(Evaluator &evaluator,
   auto ty = evaluateOrDefault(
       evaluator,
       CustomAttrTypeRequest{customAttr, var->getDeclContext(),
-                            CustomAttrTypeKind::PropertyDelegate},
+                            CustomAttrTypeKind::PropertyWrapper},
       Type());
   if (!ty || ty->hasError()) {
     return ErrorType::get(var->getASTContext());
diff --git a/lib/Sema/TypeCheckType.cpp b/lib/Sema/TypeCheckType.cpp
index 2a2040fc26505..4fd9b91dbda8c 100644
--- a/lib/Sema/TypeCheckType.cpp
+++ b/lib/Sema/TypeCheckType.cpp
@@ -3974,7 +3974,7 @@ Type CustomAttrTypeRequest::evaluate(Evaluator &eval, CustomAttr *attr,
 
   OpenUnboundGenericTypeFn unboundTyOpener = nullptr;
   // Property delegates allow their type to be an unbound generic.
-  if (typeKind == CustomAttrTypeKind::PropertyDelegate) {
+  if (typeKind == CustomAttrTypeKind::PropertyWrapper) {
     unboundTyOpener = [](auto unboundTy) {
       // FIXME: Don't let unbound generic types
       // escape type resolution. For now, just
diff --git a/test/ModuleInterface/actor_isolation.swift b/test/ModuleInterface/actor_isolation.swift
new file mode 100644
index 0000000000000..dd565f4fc4bfe
--- /dev/null
+++ b/test/ModuleInterface/actor_isolation.swift
@@ -0,0 +1,44 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -o %t/Test.swiftmodule -emit-module-interface-path %t/Test.swiftinterface -module-name Test -enable-experimental-concurrency %s
+// RUN: %FileCheck %s --check-prefix FROMSOURCE --check-prefix CHECK < %t/Test.swiftinterface
+// RUN: %target-swift-frontend -emit-module -o /dev/null -merge-modules %t/Test.swiftmodule -disable-objc-attr-requires-foundation-module -emit-module-interface-path %t/TestFromModule.swiftinterface -module-name Test -enable-experimental-concurrency
+// RUN: %FileCheck %s --check-prefix FROMMODULE --check-prefix CHECK < %t/TestFromModule.swiftinterface
+
+// REQUIRES: concurrency
+import _Concurrency
+
+// CHECK: actor public class SomeActor
+public actor class SomeActor {
+  @actorIndependent func maine() { }
+}
+
+// CHECK: @globalActor public struct SomeGlobalActor
+@globalActor
+public struct SomeGlobalActor {
+  public static let shared = SomeActor()
+}
+
+// CHECK: @{{(Test.)?}}SomeGlobalActor public protocol P1
+// CHECK-NEXT: @{{(Test.)?}}SomeGlobalActor func method()
+@SomeGlobalActor
+public protocol P1 {
+  func method()
+}
+
+// CHECK: class C1
+// CHECK-NEXT: @{{(Test.)?}}SomeGlobalActor public func method()
+public class C1: P1 {
+  public func method() { }
+}
+
+@SomeGlobalActor
+public class C2 { }
+
+// CHECK: @{{(Test.)?}}SomeGlobalActor public class C2
+public class C3: C2 { }
+
+// CHECK: actor public class SomeSubActor
+// CHECK-NEXT: @actorIndependent public func maine()
+public actor class SomeSubActor: SomeActor {
+  override public func maine() { }
+}