SE-0055: Making pointer nullability explicit

CHANGELOG.md

@@ -3,6 +3,29 @@ Note: This is in reverse chronological order, so newer entries are added to the
 Swift 3.0
 -------
 
+* As part of the changes for SE-0055 (see below), the *pointee* types of
+  imported pointers (e.g. the `id` in `id *`) are no longer assumed to always
+  be `_Nullable` even if annotated otherwise. However, an implicit or explicit
+  annotation of `_Null_unspecified` on a pointee type is still imported as
+  `Optional`.
+
+* [SE-0055](https://github.com/apple/swift-evolution/blob/master/proposals/0055-optional-unsafe-pointers.md):
+  The types `UnsafePointer`, `UnsafeMutablePointer`,
+  `AutoreleasingUnsafeMutablePointer`, `OpaquePointer`, `Selector`, and `Zone`
+  (formerly `NSZone`) now represent non-nullable pointers, i.e. pointers that
+  are never `nil`. A nullable pointer is now represented using `Optional`, e.g.
+  `UnsafePointer<Int>?` For types imported from C, non-object pointers (such as
+  `int *`) now have their nullability taken into account.
+
+  One possible area of difficulty is passing a nullable pointer to a function
+  that uses C variadics. Swift will not permit this directly, so as a
+  workaround please use the following idiom to pass it as a pointer-sized
+  integer value instead:
+
+  ```swift
+  unsafeBitCast(nullablePointer, to: Int.self)
+  ```
+
 * [SE-0046] (https://github.com/apple/swift-evolution/blob/master/proposals/0046-first-label.md) Function parameters now have consistent labelling across all function parameters. With this update the first parameter declarations will now match the existing behavior of the second and later parameters. This change makes the language simpler. 
 
     Functions that were written and called as follows 

include/swift/Runtime/Metadata.h

@@ -907,6 +907,9 @@ extern "C" const ValueWitnessTable _TWVXwGSqBo_; // weak Builtin.NativeObject?
 SWIFT_RUNTIME_EXPORT
 extern "C" const ExtraInhabitantsValueWitnessTable _TWVBb; // Builtin.BridgeObject
 
+SWIFT_RUNTIME_EXPORT
+extern "C" const ExtraInhabitantsValueWitnessTable _TWVBp; // Builtin.RawPointer
+
 #if SWIFT_OBJC_INTEROP
 // The ObjC-pointer table can be used for arbitrary ObjC pointer types.
 SWIFT_RUNTIME_EXPORT
@@ -1288,6 +1291,8 @@ extern "C" const FullOpaqueMetadata _TMBo;        // Builtin.NativeObject
 SWIFT_RUNTIME_EXPORT
 extern "C" const FullOpaqueMetadata _TMBb;        // Builtin.BridgeObject
 SWIFT_RUNTIME_EXPORT
+extern "C" const FullOpaqueMetadata _TMBp;        // Builtin.RawPointer
+SWIFT_RUNTIME_EXPORT
 extern "C" const FullOpaqueMetadata _TMBB;        // Builtin.UnsafeValueBuffer
 #if SWIFT_OBJC_INTEROP
 SWIFT_RUNTIME_EXPORT

lib/AST/ASTContext.cpp

@@ -3620,7 +3620,7 @@ ASTContext::getForeignRepresentationInfo(NominalTypeDecl *nominal,
 
     // Pre-populate the foreign-representable cache with known types.
     if (auto stdlib = getStdlibModule()) {
-      addTrivial(getIdentifier("OpaquePointer"), stdlib);
+      addTrivial(getIdentifier("OpaquePointer"), stdlib, true);
 
       // Builtin types
       // FIXME: Layering violation to use the ClangImporter's define.
@@ -3636,13 +3636,13 @@ ASTContext::getForeignRepresentationInfo(NominalTypeDecl *nominal,
     }
 
     if (auto objectiveC = getLoadedModule(Id_ObjectiveC)) {
-      addTrivial(Id_Selector, objectiveC);
+      addTrivial(Id_Selector, objectiveC, true);
 
       // Note: ObjCBool is odd because it's bridged to Bool in APIs,
       // but can also be trivially bridged.
       addTrivial(getIdentifier("ObjCBool"), objectiveC);
 
-      addTrivial(getSwiftId(KnownFoundationEntity::NSZone), objectiveC);
+      addTrivial(getSwiftId(KnownFoundationEntity::NSZone), objectiveC, true);
     }
 
     if (auto coreGraphics = getLoadedModule(getIdentifier("CoreGraphics"))) {

lib/AST/Type.cpp

@@ -2116,10 +2116,6 @@ getForeignRepresentable(Type type, ForeignLanguage language, DeclContext *dc) {
   // Pointers may be representable in ObjC.
   PointerTypeKind pointerKind;
   if (auto pointerElt = type->getAnyPointerElementType(pointerKind)) {
-    // FIXME: Optionality should be embedded in the pointer types.
-    if (wasOptional)
-      return failure();
-
     switch (pointerKind) {
     case PTK_UnsafeMutablePointer:
     case PTK_UnsafePointer:

lib/ClangImporter/ImportType.cpp

@@ -85,9 +85,8 @@ namespace {
       /// The source type is a function pointer type.
       CFunctionPointer,
 
-      /// The source type is a specially-handled pointer type (usually a mapped
-      /// typedef) that nonetheless needs to preserve nullability.
-      CustomNullablePointer,
+      /// The source type is any other pointer type.
+      OtherPointer,
     };
 
     ImportHintKind Kind;
@@ -126,7 +125,7 @@ namespace {
     case ImportHint::ObjCBridged:
     case ImportHint::ObjCPointer:
     case ImportHint::CFunctionPointer:
-    case ImportHint::CustomNullablePointer:
+    case ImportHint::OtherPointer:
       return true;
     }
   }
@@ -151,17 +150,16 @@ namespace {
   getOptionalType(Type payloadType,
                   ImportTypeKind kind,
                   OptionalTypeKind OptKind = OTK_ImplicitlyUnwrappedOptional) {
-    // Import pointee types as true Optional.
-    if (kind == ImportTypeKind::Pointee)
-      return OptionalType::get(payloadType);
-
     switch (OptKind) {
-      case OTK_ImplicitlyUnwrappedOptional:
-        return ImplicitlyUnwrappedOptionalType::get(payloadType);
-      case OTK_None:
-        return payloadType;
-      case OTK_Optional:
+    case OTK_None:
+      return payloadType;
+    case OTK_Optional:
+      return OptionalType::get(payloadType);
+    case OTK_ImplicitlyUnwrappedOptional:
+      // Import pointee types as true Optional.
+      if (kind == ImportTypeKind::Pointee)
         return OptionalType::get(payloadType);
+      return ImplicitlyUnwrappedOptionalType::get(payloadType);
     }
   }
 
@@ -292,7 +290,7 @@ namespace {
                              Impl.SwiftContext.getSwiftName(
                                KnownFoundationEntity::NSZone));
           if (wrapperTy)
-            return wrapperTy;
+            return {wrapperTy, ImportHint::OtherPointer};
         }
       }
 
@@ -315,7 +313,8 @@ namespace {
       // If the pointed-to type is unrepresentable in Swift, import as
       // OpaquePointer.
       if (!pointeeType)
-        return getOpaquePointerType();
+        return {Impl.SwiftContext.getOpaquePointerDecl()->getDeclaredType(),
+                ImportHint::OtherPointer};
 
       if (pointeeQualType->isFunctionType()) {
         auto funcTy = pointeeType->castTo<FunctionType>();
@@ -329,29 +328,29 @@ namespace {
 
       auto quals = pointeeQualType.getQualifiers();
 
-      if (quals.hasConst())
+      if (quals.hasConst()) {
         return {Impl.getNamedSwiftTypeSpecialization(Impl.getStdlibModule(),
                                                      "UnsafePointer",
                                                      pointeeType),
-                ImportHint::None};
+                ImportHint::OtherPointer};
+      }
+
       // Mutable pointers with __autoreleasing or __unsafe_unretained
       // ownership map to AutoreleasingUnsafeMutablePointer<T>.
-      else if (quals.getObjCLifetime() == clang::Qualifiers::OCL_Autoreleasing
-            || quals.getObjCLifetime() == clang::Qualifiers::OCL_ExplicitNone)
+      if (quals.getObjCLifetime() == clang::Qualifiers::OCL_Autoreleasing ||
+          quals.getObjCLifetime() == clang::Qualifiers::OCL_ExplicitNone) {
         return {
           Impl.getNamedSwiftTypeSpecialization(
             Impl.getStdlibModule(), "AutoreleasingUnsafeMutablePointer",
             pointeeType),
-            ImportHint::None};
+          ImportHint::OtherPointer};
+      }
+
       // All other mutable pointers map to UnsafeMutablePointer.
       return {Impl.getNamedSwiftTypeSpecialization(Impl.getStdlibModule(),
                                                    "UnsafeMutablePointer",
                                                    pointeeType),
-              ImportHint::None};
-    }
-
-    Type getOpaquePointerType() {
-      return Impl.getNamedSwiftType(Impl.getStdlibModule(), "OpaquePointer");
+              ImportHint::OtherPointer};
     }
 
     ImportResult VisitBlockPointerType(const clang::BlockPointerType *type) {
@@ -568,11 +567,8 @@ namespace {
           hint = ImportHint::CFPointer;
         } else if (mappedType->isAnyExistentialType()) { // id, Class
           hint = ImportHint::ObjCPointer;
-        } else if (type->isBlockPointerType()) {
-          // FIXME: This should eventually be "isAnyPointerType", but right now
-          // non-object, non-block pointers are never Optional in Swift; they
-          // just can have a value of 'nil' themselves.
-          hint = ImportHint::CustomNullablePointer;
+        } else if (type->isPointerType() || type->isBlockPointerType()) {
+          hint = ImportHint::OtherPointer;
         }
         // Any other interesting mapped types should be hinted here.
 

lib/IDE/CodeCompletion.cpp

@@ -3309,6 +3309,7 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
     // If the expected type is ObjectiveC.Selector, add #selector.
     if (Ctx.LangOpts.EnableObjCInterop) {
       for (auto T : ExpectedTypes) {
+        T = T->lookThroughAllAnyOptionalTypes();
         if (auto structDecl = T->getStructOrBoundGenericStruct()) {
           if (structDecl->getName() == Ctx.Id_Selector &&
               structDecl->getParentModule()->getName() == Ctx.Id_ObjectiveC) {

lib/IRGen/GenMeta.cpp

@@ -1765,7 +1765,8 @@ namespace {
       if (t == C.TheEmptyTupleType
           || t == C.TheNativeObjectType
           || t == C.TheUnknownObjectType
-          || t == C.TheBridgeObjectType)
+          || t == C.TheBridgeObjectType
+          || t == C.TheRawPointerType)
         return true;
       if (auto intTy = dyn_cast<BuiltinIntegerType>(t)) {
         auto width = intTy->getWidth();

lib/IRGen/GenType.cpp

@@ -411,7 +411,53 @@ namespace {
                       Alignment align)
       : PODSingleScalarTypeInfo(storage, size, std::move(spareBits), align) {}
   };
-
+
+  /// A TypeInfo implementation for bare non-null pointers (like `void *`).
+  class RawPointerTypeInfo final :
+    public PODSingleScalarTypeInfo<RawPointerTypeInfo, LoadableTypeInfo> {
+  public:
+    RawPointerTypeInfo(llvm::Type *storage, Size size, Alignment align)
+      : PODSingleScalarTypeInfo(
+          storage, size,
+          SpareBitVector::getConstant(size.getValueInBits(), false),
+          align) {}
+
+    bool mayHaveExtraInhabitants(IRGenModule &IGM) const override {
+      return true;
+    }
+
+    unsigned getFixedExtraInhabitantCount(IRGenModule &IGM) const override {
+      return 1;
+    }
+
+    APInt getFixedExtraInhabitantValue(IRGenModule &IGM, unsigned bits,
+                                       unsigned index) const override {
+      assert(index == 0);
+      return APInt(bits, 0);
+    }
+
+    llvm::Value *getExtraInhabitantIndex(IRGenFunction &IGF,
+                                         Address src,
+                                         SILType T) const override {
+      // Copied from BridgeObjectTypeInfo.
+      src = IGF.Builder.CreateBitCast(src, IGF.IGM.IntPtrTy->getPointerTo());
+      auto val = IGF.Builder.CreateLoad(src);
+      auto zero = llvm::ConstantInt::get(IGF.IGM.IntPtrTy, 0);
+      auto isNonzero = IGF.Builder.CreateICmpNE(val, zero);
+      // We either have extra inhabitant 0 or no extra inhabitant (-1).
+      // Conveniently, this is just a sext i1 -> i32 away.
+      return IGF.Builder.CreateSExt(isNonzero, IGF.IGM.Int32Ty);
+    }
+
+    void storeExtraInhabitant(IRGenFunction &IGF, llvm::Value *index,
+                              Address dest, SILType T) const override {
+      // Copied from BridgeObjectTypeInfo.
+      // There's only one extra inhabitant, 0.
+      dest = IGF.Builder.CreateBitCast(dest, IGF.IGM.IntPtrTy->getPointerTo());
+      IGF.Builder.CreateStore(llvm::ConstantInt::get(IGF.IGM.IntPtrTy, 0),dest);
+    }
+  };
+
   /// A TypeInfo implementation for opaque storage. Swift will preserve any
   /// data stored into this arbitrarily sized and aligned field, but doesn't
   /// know anything about the data.
@@ -720,6 +766,20 @@ const LoadableTypeInfo &TypeConverter::getBridgeObjectTypeInfo() {
   return *BridgeObjectTI;
 }
 
+const LoadableTypeInfo &IRGenModule::getRawPointerTypeInfo() {
+  return Types.getRawPointerTypeInfo();
+}
+
+const LoadableTypeInfo &TypeConverter::getRawPointerTypeInfo() {
+  if (RawPointerTI) return *RawPointerTI;
+  RawPointerTI = new RawPointerTypeInfo(IGM.Int8PtrTy,
+                                        IGM.getPointerSize(),
+                                        IGM.getPointerAlignment());
+  RawPointerTI->NextConverted = FirstType;
+  FirstType = RawPointerTI;
+  return *RawPointerTI;
+}
+
 const LoadableTypeInfo &TypeConverter::getEmptyTypeInfo() {
   if (EmptyTI) return *EmptyTI;
   EmptyTI = new EmptyTypeInfo(IGM.Int8Ty);
@@ -1263,6 +1323,7 @@ TypeCacheEntry TypeConverter::convertType(CanType ty) {
                            getFixedBufferSize(IGM),
                            getFixedBufferAlignment(IGM));
   case TypeKind::BuiltinRawPointer:
+    return &getRawPointerTypeInfo();
   case TypeKind::BuiltinFloat:
   case TypeKind::BuiltinInteger:
   case TypeKind::BuiltinVector: {

lib/IRGen/GenType.h

@@ -86,6 +86,7 @@ class TypeConverter {
   const LoadableTypeInfo *NativeObjectTI = nullptr;
   const LoadableTypeInfo *UnknownObjectTI = nullptr;
   const LoadableTypeInfo *BridgeObjectTI = nullptr;
+  const LoadableTypeInfo *RawPointerTI = nullptr;
   const LoadableTypeInfo *WitnessTablePtrTI = nullptr;
   const LoadableTypeInfo *TypeMetadataPtrTI = nullptr;
   const LoadableTypeInfo *ObjCClassPtrTI = nullptr;
@@ -148,6 +149,7 @@ class TypeConverter {
   const LoadableTypeInfo &getNativeObjectTypeInfo();
   const LoadableTypeInfo &getUnknownObjectTypeInfo();
   const LoadableTypeInfo &getBridgeObjectTypeInfo();
+  const LoadableTypeInfo &getRawPointerTypeInfo();
   const LoadableTypeInfo &getTypeMetadataPtrTypeInfo();
   const LoadableTypeInfo &getObjCClassPtrTypeInfo();
   const LoadableTypeInfo &getWitnessTablePtrTypeInfo();

lib/IRGen/IRGenModule.h

@@ -550,6 +550,7 @@ class IRGenModule {
   const LoadableTypeInfo &getNativeObjectTypeInfo();
   const LoadableTypeInfo &getUnknownObjectTypeInfo();
   const LoadableTypeInfo &getBridgeObjectTypeInfo();
+  const LoadableTypeInfo &getRawPointerTypeInfo();
   llvm::Type *getStorageTypeForUnlowered(Type T);
   llvm::Type *getStorageTypeForLowered(CanType T);
   llvm::Type *getStorageType(SILType T);

lib/PrintAsObjC/PrintAsObjC.cpp

@@ -430,7 +430,7 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
       // parameter, print it.
       if (errorConvention && i == errorConvention->getErrorParameterIndex()) {
         os << piece << ":(";
-        print(errorConvention->getErrorParameterType(), OTK_None);
+        print(errorConvention->getErrorParameterType(), None);
         os << ")error";
         continue;
       }
@@ -918,10 +918,8 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
       return false;
 
     os << iter->second.first;
-    if (iter->second.second) {
-      // FIXME: Selectors and pointers should be nullable.
-      printNullability(OptionalTypeKind::OTK_ImplicitlyUnwrappedOptional);
-    }
+    if (iter->second.second)
+      printNullability(optionalKind);
     return true;
   }
 
@@ -932,13 +930,6 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
     os << " */";
   }
 
-  bool isClangObjectPointerType(const clang::TypeDecl *clangTypeDecl) const {
-    ASTContext &ctx = M.getASTContext();
-    auto &clangASTContext = ctx.getClangModuleLoader()->getClangASTContext();
-    clang::QualType clangTy = clangASTContext.getTypeDeclType(clangTypeDecl);
-    return clangTy->isObjCRetainableType();
-  }
-
   bool isClangPointerType(const clang::TypeDecl *clangTypeDecl) const {
     ASTContext &ctx = M.getASTContext();
     auto &clangASTContext = ctx.getClangModuleLoader()->getClangASTContext();
@@ -958,13 +949,9 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
       auto *clangTypeDecl = cast<clang::TypeDecl>(alias->getClangDecl());
       os << clangTypeDecl->getName();
 
-      // Print proper nullability for CF types, but _Null_unspecified for
-      // all other non-object Clang pointer types.
       if (aliasTy->hasReferenceSemantics() ||
-          isClangObjectPointerType(clangTypeDecl)) {
+          isClangPointerType(clangTypeDecl)) {
         printNullability(optionalKind);
-      } else if (isClangPointerType(clangTypeDecl)) {
-        printNullability(OptionalTypeKind::OTK_ImplicitlyUnwrappedOptional);
       }
       return;
     }
@@ -1069,8 +1056,7 @@ class ObjCPrinter : private DeclVisitor<ObjCPrinter>,
     if (isConst)
       os << " const";
     os << " *";
-    // FIXME: Pointer types should be nullable.
-    printNullability(OptionalTypeKind::OTK_ImplicitlyUnwrappedOptional);
+    printNullability(optionalKind);
     return true;
   }