Allow extensions to define private module methods

lib/AST/NameLookup.cpp

@@ -1726,12 +1726,17 @@ shouldDiagnoseConflict(NominalTypeDecl *ty, AbstractFunctionDecl *newDecl,
   // bridging header? Some code bases implement ObjC methods in Swift even
   // though it's not exactly supported.
   auto newDeclModuleName = newDecl->getModuleContext()->getName();
+  auto newDeclPrivateModuleName = newDecl->getASTContext().getIdentifier(
+                     (llvm::Twine(newDeclModuleName.str()) + "_Private").str());
+  auto bridgingHeaderModuleName = newDecl->getASTContext().getIdentifier(
+                                                     CLANG_HEADER_MODULE_NAME);
   if (llvm::all_of(vec, [&](AbstractFunctionDecl *oldDecl) {
     if (!oldDecl->hasClangNode())
       return false;
     auto oldDeclModuleName = oldDecl->getModuleContext()->getName();
     return oldDeclModuleName == newDeclModuleName
-               || oldDeclModuleName.str() == CLANG_HEADER_MODULE_NAME;
+               || oldDeclModuleName == newDeclPrivateModuleName
+               || oldDeclModuleName == bridgingHeaderModuleName;
   }))
     return false;
 

test/ClangImporter/Inputs/custom-modules/module.map

@@ -271,8 +271,3 @@ module CommonName {
   header "CommonName.h"
   export *
 }
-
-module objc_init_redundant {
-  header "objc_init_redundant.h"
-  export *
-}

test/ClangImporter/Inputs/frameworks/objc_init_redundant.framework/Modules/module.modulemap

@@ -0,0 +1,4 @@
+framework module objc_init_redundant {
+  header "objc_init_redundant.h"
+  export *
+}

test/ClangImporter/Inputs/frameworks/objc_init_redundant.framework/Modules/module.private.modulemap

@@ -0,0 +1,4 @@
+framework module objc_init_redundant_Private {
+  header "objc_init_redundant_priv.h"
+  export *
+}

test/ClangImporter/Inputs/frameworks/objc_init_redundant.framework/PrivateHeaders/objc_init_redundant_priv.h

@@ -0,0 +1,7 @@
+#import <Foundation.h>
+
+@interface MyPrivateObject : NSObject
+
+- (void)implementedInSwift;
+
+@end

test/ClangImporter/objc_init_redundant.swift

@@ -1,10 +1,11 @@
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk -I %S/Inputs/custom-modules) -import-underlying-module -import-objc-header %S/Inputs/objc_init_redundant_bridging.h -emit-sil %s -verify
-// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk -I %S/Inputs/custom-modules) -import-underlying-module -import-objc-header %S/Inputs/objc_init_redundant_bridging.h -emit-sil %s > %t.log 2>&1
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk -I %S/Inputs/custom-modules -F %S/Inputs/frameworks) -import-underlying-module -import-objc-header %S/Inputs/objc_init_redundant_bridging.h -emit-sil %s -verify
+// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk -I %S/Inputs/custom-modules -F %S/Inputs/frameworks) -import-underlying-module -import-objc-header %S/Inputs/objc_init_redundant_bridging.h -emit-sil %s > %t.log 2>&1
 // RUN: %FileCheck %s < %t.log
 
 // REQUIRES: objc_interop
 
 import Foundation
+@_implementationOnly import objc_init_redundant_Private
 
 // rdar://problem/17687082
 extension NSObject {
@@ -28,3 +29,8 @@ extension MyObject {
 extension MyBridgedObject {
   @objc func implementedInSwift() {}
 }
+
+// ...or the private module
+extension MyPrivateObject {
+  @objc func implementedInSwift() {}
+}