[CodeCompletion] Handle clang async attributes for visibilities

Control 'async' variant of imported ObjC methods.

For non-'async' variant:
1) if 'swift_private' is specified, hide.

For 'async' variant:
1) if 'swift_async(swift_private)' is specified, hide.
2) if 'swift_async(not_swift_private)' is specified, show.
3) if 'swift_async_name()' is specified, show.
4) if 'swift_private' is specified, hide.

rdar://80602940

Author: rintaro

lib/AST/Decl.cpp

@@ -3324,8 +3324,32 @@ bool ValueDecl::shouldHideFromEditor() const {
   if (AvailableAttr::isUnavailable(this))
     return true;
 
+  // Hide 'swift_private' clang decls. They are imported with '__' prefix.
   if (auto *ClangD = getClangDecl()) {
-    if (ClangD->hasAttr<clang::SwiftPrivateAttr>())
+    bool bypassSwiftPrivate = false;
+    if (auto *AFD = dyn_cast<AbstractFunctionDecl>(this)) {
+      if (AFD->getForeignAsyncConvention().hasValue()) {
+        // For imported 'async' declartions, visibility can be controlled by
+        // 'swift_async(...)' attribute.
+        if (auto *asyncAttr = ClangD->getAttr<clang::SwiftAsyncAttr>()) {
+          bypassSwiftPrivate = true;
+          switch (asyncAttr->getKind()) {
+          case clang::SwiftAsyncAttr::None:
+            // Should be unreachable.
+            return true;
+          case clang::SwiftAsyncAttr::SwiftPrivate:
+            // Hide 'swift_async(swift_private, ...)'.
+            return true;
+          case clang::SwiftAsyncAttr::NotSwiftPrivate:
+            break;
+          }
+        } else if (ClangD->getAttr<clang::SwiftAsyncNameAttr>()) {
+          // Manually specifying the name bypasses 'swift_private' attr.
+          bypassSwiftPrivate = true;
+        }
+      }
+    }
+    if (!bypassSwiftPrivate && ClangD->hasAttr<clang::SwiftPrivateAttr>())
       return true;
   }
 

test/IDE/complete_async_imported.swift

@@ -0,0 +1,50 @@
+// REQUIRES: objc_interop
+// REQUIRES: concurrency
+
+// RUN: %empty-directory(%t)
+// RUN: %empty-directory(%t/out)
+// RUN: split-file %s %t
+// RUN: %target-swift-ide-test(mock-sdk: %clang-importer-sdk) -swift-version 5.6 -batch-code-completion -source-filename %t/test.swift -filecheck %raw-FileCheck -completion-output-dir %t/out -import-objc-header %t/ObjC.h -enable-objc-interop 
+
+
+//--- ObjC.h
+
+
+@import Foundation;
+
+_Pragma("clang assume_nonnull begin")
+
+@interface MyObjCClass: NSObject
+
+- (void)method1WithCompletionHandler:(void (^)(NSError * _Nullable err))completionHandler;
+- (void)method2WithCompletionHandler:(void (^)(NSError * _Nullable err))completionHandler __attribute__((swift_private));
+- (void)method3WithCompletionHandler:(void (^)(NSError * _Nullable err))completionHandler __attribute__((swift_private)) __attribute__((swift_async_name("named3()")));
+- (void)method4WithCompletionHandler:(void (^)(NSError * _Nullable err))completionHandler __attribute__((swift_async(swift_private, 1)));
+- (void)method5WithCompletionHandler:(void (^)(NSError * _Nullable err))completionHandler __attribute__((swift_async(swift_private, 1))) __attribute__((swift_async_name("named5()")));
+- (void)method6WithCompletionHandler:(void (^)(NSError * _Nullable err))completionHandler __attribute__((swift_async(not_swift_private, 1)));
+- (void)method7WithCompletionHandler:(void (^)(NSError * _Nullable err))completionHandler __attribute__((swift_async(not_swift_private, 1))) __attribute__((swift_async_name("named7()")));
+
+@end
+
+_Pragma("clang assume_nonnull end")
+
+//--- test.swift
+
+func test(obj: MyObjCClass) async throws {
+    obj.#^COMPLETE^#
+// COMPLETE: Begin completions
+// COMPLETE-NOT: method2(
+// COMPLETE-NOT: method4()
+// COMPLETE-NOT: method5()
+// COMPLETE-DAG: Keyword[self]/CurrNominal:          self[#MyObjCClass#]; name=self
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   method1({#completionHandler: (Error?) -> Void##(Error?) -> Void#})[#Void#];
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   method1()[' async'][' throws'][#Void#];
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   named3()[' async'][' throws'][#Void#];
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   method4({#completionHandler: (Error?) -> Void##(Error?) -> Void#})[#Void#];
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   method5({#completionHandler: (Error?) -> Void##(Error?) -> Void#})[#Void#];
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   method6({#completionHandler: (Error?) -> Void##(Error?) -> Void#})[#Void#];
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   method6()[' async'][' throws'][#Void#];
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   method7({#completionHandler: (Error?) -> Void##(Error?) -> Void#})[#Void#];
+// COMPLETE-DAG: Decl[InstanceMethod]/CurrNominal:   named7()[' async'][' throws'][#Void#];
+// COMPLETE: End completions
+}