[Concurrency] Fix async throws import nullability in the presence of typedefs.

Author: DougGregor

lib/ClangImporter/ImportType.cpp

@@ -621,7 +621,9 @@ namespace {
         // handler that can also express a thrown error.
         ImportTypeKind paramImportKind = ImportTypeKind::Parameter;
         unsigned paramIdx = param - type->param_type_begin();
-        if (type == CompletionHandlerType &&
+        if (CompletionHandlerType &&
+            Impl.getClangASTContext().hasSameType(
+                CompletionHandlerType, type) &&
             paramIdx != CompletionHandlerErrorParamIndex) {
           paramImportKind = ImportTypeKind::CompletionHandlerResultParameter;
         }
@@ -1585,6 +1587,8 @@ ImportedType ClangImporter::Implementation::importType(
     if (auto blockPtrType = type->getAs<clang::BlockPointerType>()) {
       completionHandlerType =
           blockPtrType->getPointeeType()->castAs<clang::FunctionType>();
+
+      type = clang::QualType(blockPtrType, 0);
     }
   }
 

test/IDE/print_clang_objc_async.swift

@@ -21,6 +21,7 @@
 // CHECK-DAG:     func findAnswerFailingly(completionHandler handler: @escaping (String?, Error?) -> Void) throws
 // CHECK-DAG:     func findAnswerFailingly() async throws -> String
 // CHECK-DAG:     func findQAndA() async throws -> (String?, String)
+// CHECK-DAG:     func findQuestionableAnswers() async throws -> (String, String?)
 // CHECK-DAG:     func doSomethingFun(_ operation: String) async
 // CHECK: {{^[}]$}}
 

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

@@ -8,6 +8,8 @@
 -(void)allOperationsWithCompletionHandler:(void (^)(NSArray<NSString *> *))completion;
 @end
 
+typedef void (^CompletionHandler)(NSString * _Nullable, NSString * _Nullable_result, NSError * _Nullable);
+
 @interface SlowServer : NSObject <ServiceProvider>
 -(void)doSomethingSlow:(NSString *)operation completionHandler:(void (^)(NSInteger))handler;
 -(void)doSomethingDangerous:(NSString *)operation completionHandler:(void (^ _Nullable)(NSString *_Nullable, NSError * _Nullable))handler;
@@ -18,6 +20,7 @@
 -(void)findAnswerAsynchronously:(void (^)(NSString *_Nullable, NSError * _Nullable))handler __attribute__((swift_name("findAnswer(completionHandler:)")));
 -(BOOL)findAnswerFailinglyWithError:(NSError * _Nullable * _Nullable)error completion:(void (^)(NSString *_Nullable, NSError * _Nullable))handler __attribute__((swift_name("findAnswerFailingly(completionHandler:)")));
 -(void)findQAndAWithCompletionHandler:(void (^)(NSString *_Nullable_result, NSString *_Nullable answer, NSError * _Nullable))handler;
+-(void)findQuestionableAnswersWithCompletionHandler:(CompletionHandler)handler;
 -(void)doSomethingFun:(NSString *)operation then:(void (^)(void))completionHandler;
 -(void)getFortuneAsynchronouslyWithCompletionHandler:(void (^)(NSString *_Nullable, NSError * _Nullable))handler;
 -(void)getMagicNumberAsynchronouslyWithSeed:(NSInteger)seed completionHandler:(void (^)(NSInteger, NSError * _Nullable))handler;