[Clang importer] Don't suppress properties due to async method imports.

The Clang importer had some logic to suppress the import of a property that
had the same name as a method with no parameters. This logic
inadvertently meant that an async import of a completion-handler method
could prevent a (non-async) property of the same name to not be
imported, breaking existing code. In such cases, don't suppress the
property import.

Fixes rdar://73326019.

Author: DougGregor

lib/ClangImporter/ImportDecl.cpp

@@ -2177,6 +2177,11 @@ namespace {
           if (!fd->getName().getArgumentNames().empty())
             continue;
 
+          // async methods don't conflict with properties because of sync/async
+          // overloading.
+          if (fd->hasAsync())
+            continue;
+
           foundMethod = true;
         } else if (auto *var = dyn_cast<VarDecl>(result)) {
           if (var->isInstanceMember() != decl->isInstanceProperty())

test/ClangImporter/objc_async.swift

@@ -46,6 +46,9 @@ func testSlowServer(slowServer: SlowServer) async throws {
   slowServer.repeatTrick("jump") // expected-error{{missing argument for parameter 'completionHandler' in call}}
 
   _ = try await slowServer.someAsyncMethod()
+
+
+  _ = await slowServer.operations()
 }
 
 func testSlowServerSynchronous(slowServer: SlowServer) {
@@ -57,6 +60,9 @@ func testSlowServerSynchronous(slowServer: SlowServer) {
   slowServer.dance("jig") { s in print(s + "") }
   slowServer.leap(17) { s in print(s + "") }
   slowServer.repeatTrick("jump") { i in print(i + 1) }
+
+  let s = slowServer.operations
+  _ = s + []
 }
 
 func testSlowServerOldSchool(slowServer: SlowServer) {

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

@@ -57,6 +57,10 @@ typedef void (^CompletionHandler)(NSString * _Nullable, NSString * _Nullable_res
 -(void)oldAPIWithCompletionHandler:(void (^ _Nonnull)(NSString *_Nullable, NSError *_Nullable))handler __attribute__((availability(macosx, deprecated=10.14)));
 
 -(void)someAsyncMethodWithBlock:(void (^ _Nonnull)(NSString *_Nullable, NSError *_Nullable))completionHandler;
+
+// Property & async method overloading
+-(void)getOperationsWithCompletionHandler:(void (^)(NSArray<NSString *> *))handler;
+@property (readonly, nonatomic) NSArray<NSString *> *operations;
 @end
 
 @protocol RefrigeratorDelegate<NSObject>