[ClangImporter] Import NS_OPTIONS 0 values with explicit Swift-names.

This shows that the owner of the option set has thought about the
zero case, and wants it to be available in Swift, rather than disabling
it with the default "use [] to construct an empty option set" message.

rdar://problem/26290766

Author: jrose-apple

lib/ClangImporter/ImportDecl.cpp

@@ -2066,7 +2066,8 @@ namespace {
                                const clang::EnumDecl *clangEnum,
                                NominalTypeDecl *theStruct) {
       Optional<ImportedName> swift3Name;
-      auto name = importFullName(decl, swift3Name).Imported.getBaseName();
+      ImportedName nameInfo = importFullName(decl, swift3Name);
+      Identifier name = nameInfo.Imported.getBaseName();
       if (name.empty())
         return nullptr;
 
@@ -2083,7 +2084,8 @@ namespace {
       // NS_OPTIONS members that have a value of 0 (typically named "None") do
       // not operate as a set-like member.  Mark them unavailable with a message
       // that says that they should be used as [].
-      if (!decl->getInitVal() && !CD->getAttrs().hasAttribute<AvailableAttr>()){
+      if (decl->getInitVal() == 0 && !nameInfo.HasCustomName &&
+          !CD->getAttrs().isUnavailable(Impl.SwiftContext)) {
         /// Create an AvailableAttr that indicates specific availability
         /// for all platforms.
         auto attr =

test/ClangModules/enum.swift

@@ -179,3 +179,14 @@ let audioComponentFlags2: FakeAudioComponentFlags = [.loadOutOfProcess]
 let objcFlags: objc_flags = [.taggedPointer, .swiftRefcount]
 
 let optionsWithSwiftName: NSOptionsAlsoGetSwiftName = .Case
+
+// <rdar://problem/25168818> Don't import None members in NS_OPTIONS types
+#if !IRGEN
+let _ = NSRuncingOptions.none // expected-error {{'none' is unavailable: use [] to construct an empty option set}}
+#endif
+// ...but do if they have a custom name
+_ = EmptySet1.default
+// ...even if the custom name is the same as the name they would have had
+_ = EmptySet2.none
+// ...or the original name.
+_ = EmptySet3.None

test/ClangModules/objc_parse.swift

@@ -598,7 +598,3 @@ func testNSUInteger(_ obj: NSUIntegerTests, uint: UInt, int: Int) {
   let _: String = num.uintValue // expected-error {{cannot convert value of type 'UInt' to specified type 'String'}}
 }
 
-
-// <rdar://problem/25168818> Don't import None members in NS_OPTIONS types
-let _ = NSRuncingOptions.none // expected-error {{'none' is unavailable: use [] to construct an empty option set}}
-

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

@@ -52,3 +52,13 @@ typedef CF_ENUM(UInt32, AU3DMixerAttenuationCurve) {
   k3DMixerAttenuationCurve_Inverse = 2,
   k3DMixerAttenuationCurve_Linear = 3
 };
+
+typedef CF_OPTIONS(UInt32, EmptySet1) {
+  kEmptySet1DefaultOptions __attribute__((swift_name("default")))
+};
+typedef CF_OPTIONS(UInt32, EmptySet2) {
+  kEmptySet2None __attribute__((swift_name("none")))
+};
+typedef CF_OPTIONS(UInt32, EmptySet3) {
+  kEmptySet3None __attribute__((swift_name("None")))
+};