[concurrency] Ensure that we treat closures that are nonisolated(nonsending) via their ActorIsolation as nonisolated(nonsending).

lib/SIL/IR/SILFunctionType.cpp

@@ -2633,6 +2633,9 @@ static CanSILFunctionType getSILFunctionType(
         } else if (decl->getAttrs().hasAttribute<ConcurrentAttr>()) {
           actorIsolation = ActorIsolation::forNonisolated(false /*unsafe*/);
         }
+      } else if (auto *closure = constant->getAbstractClosureExpr()) {
+        if (auto isolation = closure->getActorIsolation())
+          actorIsolation = isolation;
       }
 
       if (!actorIsolation) {

lib/SILGen/SILGen.cpp

@@ -765,6 +765,13 @@ static ActorIsolation getActorIsolationForFunction(SILFunction &fn) {
       return ActorIsolation::forNonisolated(false);
     }
 
+    // If we have a closure expr, check if our type is
+    // nonisolated(nonsending). In that case, we use that instead.
+    if (auto *closureExpr = constant.getAbstractClosureExpr()) {
+      if (auto actorIsolation = closureExpr->getActorIsolation())
+        return actorIsolation;
+    }
+
     // If we have actor isolation for our constant, put the isolation onto the
     // function. If the isolation is unspecified, we do not return it.
     if (auto isolation =

lib/Sema/CSApply.cpp

@@ -1346,8 +1346,32 @@ namespace {
           new (ctx) AutoClosureExpr(/*set body later*/ nullptr, thunkTy, dc);
       thunk->setParameterList(thunkParamList);
       thunk->setThunkKind(AutoClosureExpr::Kind::SingleCurryThunk);
+
+      // TODO: We should do this in the ActorIsolation checker but for now it is
+      // too risky. This is a narrow fix for 6.2.
+      //
+      // The problem that this is working around is given an autoclosure that
+      // returns an autoclosure that partially applies over an instance method,
+      // we do not visit the inner autoclosure in the ActorIsolation checker
+      // meaning that we do not properly call setActorIsolation on the
+      // AbstractClosureExpr that we produce here.
+      switch (thunkTy->getIsolation().getKind()) {
+      case FunctionTypeIsolation::Kind::NonIsolated:
+      case FunctionTypeIsolation::Kind::Parameter:
+      case FunctionTypeIsolation::Kind::Erased:
+        break;
+      case FunctionTypeIsolation::Kind::GlobalActor:
+        thunk->setActorIsolation(ActorIsolation::forGlobalActor(
+            thunkTy->getIsolation().getGlobalActorType()));
+        break;
+      case FunctionTypeIsolation::Kind::NonIsolatedCaller:
+        thunk->setActorIsolation(
+            ActorIsolation::forCallerIsolationInheriting());
+        break;
+      }
+
       cs.cacheType(thunk);
-      
+
       // If the `self` type is existential, it must be opened.
       OpaqueValueExpr *baseOpened = nullptr;
       Expr *origBaseExpr = baseExpr;

test/Inputs/clang-importer-sdk/usr/include/ObjCConcurrency.h

@@ -123,6 +123,16 @@ typedef void (^NonsendableCompletionHandler)(NSString * _Nullable, NSString * _N
     __attribute__((swift_async_error(zero_argument, 3)));
 - (void)getIceCreamFlavorWithCompletionHandler:
     (void (^)(Flavor flavor, NSError *__nullable error))completionHandler;
+
+@property(class, strong, readonly) SlowServer *standardServer;
+- (void)getValueWithKey:(NSString *)valueIdentifier
+             completion:(void (^)(NSString *__nullable value,
+                                  NSError *__nullable error))completionHandler;
+- (void)getMainActorValueWithKey:(NSString *)valueIdentifier
+                      completion:
+                          (void (^)(NSString *__nullable value,
+                                    NSError *__nullable error))completionHandler
+    MAIN_ACTOR;
 @end
 
 @protocol RefrigeratorDelegate<NSObject>