Stage implementation of SE-0033 behind a flag, -enable-swift-newtype.

We're going to quarantine this feature behind a frontend flag for a
bit.

Author: DougGregor

include/swift/ClangImporter/ClangImporterOptions.h

@@ -70,6 +70,9 @@ class ClangImporterOptions {
 
   /// If true ignore the swift bridged attribute.
   bool DisableSwiftBridgeAttr = false;
+
+  /// Whether we should honor the swift_newtype attribute.
+  bool HonorSwiftNewtypeAttr = false;
 };
 
 } // end namespace swift

include/swift/Option/FrontendOptions.td

@@ -232,6 +232,10 @@ def enable_infer_import_as_member :
   Flag<["-"], "enable-infer-import-as-member">,
   HelpText<"Infer when a global could be imported as a member">;
 
+def enable_swift_newtype :
+  Flag<["-"], "enable-swift-newtype">,
+  HelpText<"Enable the swift_newtype attribute">;
+
 def enable_strip_ns_prefix :
   Flag<["-"], "enable-strip-ns-prefix">,
   HelpText<"Strip 'NS' prefix from Foundation entities">;

lib/ClangImporter/ClangImporter.cpp

@@ -1209,6 +1209,7 @@ ClangImporter::Implementation::Implementation(ASTContext &ctx,
     ImportForwardDeclarations(opts.ImportForwardDeclarations),
     InferImportAsMember(opts.InferImportAsMember),
     DisableSwiftBridgeAttr(opts.DisableSwiftBridgeAttr),
+    HonorSwiftNewtypeAttr(opts.HonorSwiftNewtypeAttr),
     BridgingHeaderLookupTable(nullptr)
 {
   // Add filters to determine if a Clang availability attribute
@@ -2032,7 +2033,10 @@ static bool moduleIsInferImportAsMember(const clang::NamedDecl *decl,
 
 // If this decl is associated with a swift_newtype typedef, return it, otherwise
 // null
-static clang::TypedefNameDecl *findSwiftNewtype(const clang::Decl *decl) {
+static clang::TypedefNameDecl *findSwiftNewtype(const clang::Decl *decl,
+                                                bool honorSwiftNewtypeAttr) {
+  if (!honorSwiftNewtypeAttr) return nullptr;
+
   if (auto varDecl = dyn_cast<clang::VarDecl>(decl))
     if (auto typedefTy = varDecl->getType()->getAs<clang::TypedefType>())
       if (typedefTy->getDecl()->hasAttr<clang::SwiftNewtypeAttr>())
@@ -2076,7 +2080,7 @@ auto ClangImporter::Implementation::importFullName(
       break;
     }
   // Import onto a swift_newtype if present
-  } else if (auto newtypeDecl = findSwiftNewtype(D)) {
+  } else if (auto newtypeDecl = findSwiftNewtype(D, HonorSwiftNewtypeAttr)) {
     result.EffectiveContext = newtypeDecl;
   // Everything else goes into its redeclaration context.
   } else {
@@ -2551,7 +2555,7 @@ auto ClangImporter::Implementation::importFullName(
 
   // swift_newtype-ed declarations may have common words with the type name
   // stripped.
-  if (auto newtypeDecl = findSwiftNewtype(D)) {
+  if (auto newtypeDecl = findSwiftNewtype(D, HonorSwiftNewtypeAttr)) {
     // Skip a leading 'k' in a 'kConstant' pattern
     if (baseName.size() >= 2 && baseName[0] == 'k' &&
         clang::isUppercase(baseName[1]))

lib/ClangImporter/ImportDecl.cpp

@@ -1276,7 +1276,7 @@ namespace {
         return nullptr;
 
       // Check for swift_newtype
-      if (!SwiftType) {
+      if (!SwiftType && Impl.HonorSwiftNewtypeAttr) {
         if (auto newtypeAttr =
                 Decl->template getAttr<clang::SwiftNewtypeAttr>()) {
           switch (newtypeAttr->getNewtypeKind()) {

lib/ClangImporter/ImportType.cpp

@@ -548,7 +548,8 @@ namespace {
       Type mappedType = decl->getDeclaredType();
       ImportHint hint = ImportHint::None;
 
-      if (type->getDecl()->hasAttr<clang::SwiftNewtypeAttr>()) {
+      if (Impl.HonorSwiftNewtypeAttr &&
+          type->getDecl()->hasAttr<clang::SwiftNewtypeAttr>()) {
         hint = ImportHint::SwiftNewtype;
 
       // For certain special typedefs, we don't want to use the imported type.

lib/ClangImporter/ImporterImpl.h

@@ -263,6 +263,7 @@ class LLVM_LIBRARY_VISIBILITY ClangImporter::Implementation
   const bool ImportForwardDeclarations;
   const bool InferImportAsMember;
   const bool DisableSwiftBridgeAttr;
+  const bool HonorSwiftNewtypeAttr;
 
   constexpr static const char * const moduleImportBufferName =
     "<swift-imported-modules>";

lib/Frontend/CompilerInvocation.cpp

@@ -894,6 +894,7 @@ static bool ParseClangImporterArgs(ClangImporterOptions &Opts,
   }
 
   Opts.InferImportAsMember |= Args.hasArg(OPT_enable_infer_import_as_member);
+  Opts.HonorSwiftNewtypeAttr |= Args.hasArg(OPT_enable_swift_newtype);
   Opts.DumpClangDiagnostics |= Args.hasArg(OPT_dump_clang_diagnostics);
 
   if (Args.hasArg(OPT_embed_bitcode))

test/IDE/newtype.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-ide-test(mock-sdk: %clang-importer-sdk) -I %t -I %S/Inputs/custom-modules -print-module -source-filename %s -module-to-print=Newtype > %t.printed.A.txt
+// RUN: %target-swift-ide-test(mock-sdk: %clang-importer-sdk) -I %t -I %S/Inputs/custom-modules -enable-swift-newtype -print-module -source-filename %s -module-to-print=Newtype > %t.printed.A.txt
 // RUN: FileCheck %s -check-prefix=PRINT -strict-whitespace < %t.printed.A.txt
 // REQUIRES: objc_interop
 
@@ -32,7 +32,7 @@
 // PRINT-NEXT:    static let thirdEntry: ClosedEnum
 // PRINT-NEXT:  }
 
-// RUN: %target-parse-verify-swift -I %S/Inputs/custom-modules
+// RUN: %target-parse-verify-swift -I %S/Inputs/custom-modules -enable-swift-newtype
 import Newtype
 
 func tests() {
@@ -50,4 +50,4 @@ func tests() {
 	let _ = ErrorDomain(rawValue: thirdEnum.rawValue)
 	let _ = ClosedEnum(rawValue: errOne.rawValue)
 
-}
+}

test/IRGen/newtype.swift

@@ -1,4 +1,4 @@
-// RUN// RUN: %target-swift-frontend -I %S/../IDE/Inputs/custom-modules %s -emit-ir | FileCheck %s
+// RUN// RUN: %target-swift-frontend -I %S/../IDE/Inputs/custom-modules %s -emit-ir -enable-swift-newtype | FileCheck %s
 import Newtype
 
 // REQUIRES: objc_interop

tools/swift-ide-test/swift-ide-test.cpp

@@ -300,6 +300,11 @@ InferImportAsMember("enable-infer-import-as-member",
                    llvm::cl::desc("Infer when a global could be imported as a member"),
                    llvm::cl::init(false));
 
+static llvm::cl::opt<bool>
+HonorSwiftNewtypeAttr("enable-swift-newtype",
+                      llvm::cl::desc("Enable swift_newtype import"),
+                      llvm::cl::init(false));
+
 static llvm::cl::opt<bool>
 StripNSPrefix("enable-strip-ns-prefix",
               llvm::cl::desc("Strip the NS prefix from Foundation et al"),
@@ -2680,11 +2685,14 @@ int main(int argc, char *argv[]) {
       options::CodeCompleteInitsInPostfixExpr;
   InitInvok.getLangOptions().Swift3Migration |= options::Swift3Migration;
   InitInvok.getLangOptions().InferImportAsMember |=
-    options::InferImportAsMember;  InitInvok.getLangOptions().StripNSPrefix |= options::StripNSPrefix;
+    options::InferImportAsMember;
+  InitInvok.getLangOptions().StripNSPrefix |= options::StripNSPrefix;
   InitInvok.getClangImporterOptions().ImportForwardDeclarations |=
     options::ObjCForwardDeclarations;
   InitInvok.getClangImporterOptions().InferImportAsMember |=
     options::InferImportAsMember;
+  InitInvok.getClangImporterOptions().HonorSwiftNewtypeAttr |=
+    options::HonorSwiftNewtypeAttr;
   if (!options::ResourceDir.empty()) {
     InitInvok.setRuntimeResourcePath(options::ResourceDir);
   }