Revert "[VM/nnbd] Make Nullability and NNBDMode class enums to avoid name conflicts."

This reverts commit d45c3d15cb.

Reason for revert: Please see https://buganizer.corp.google.com/issues/144304690
(This CL is dependent on https://dart-review.googlesource.com/c/sdk/+/124480 which caused the regression).

Original change's description:
> [VM/nnbd] Make Nullability and NNBDMode class enums to avoid name conflicts.
> 
> Change-Id: Ic78d3f48964bb61cbd1d90a69fcd68b4f29071e4
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/124587
> Commit-Queue: Régis Crelier <regis@google.com>
> Reviewed-by: Alexander Markov <alexmarkov@google.com>

TBR=alexmarkov@google.com,regis@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I24603236f04bd2ec1ad80789d78cca89e70fb1d1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/125101
Reviewed-by: Siva Annamalai <asiva@google.com>

runtime/lib/mirrors.cc

@@ -633,17 +633,16 @@ static RawInstance* CreateTypeMirror(const AbstractType& type) {
     // TODO(regis): Until mirrors reflect nullability, force kLegacy, except for
     // Null type, which should remain nullable.
     if (!type.IsNullType()) {
-      const Type& legacy_type = Type::Handle(
-          Type::Cast(type).ToNullability(Nullability::kLegacy, Heap::kOld));
+      const Type& legacy_type =
+          Type::Handle(Type::Cast(type).ToNullability(kLegacy, Heap::kOld));
       return CreateClassMirror(cls, legacy_type, Bool::False(),
                                Object::null_instance());
     }
     return CreateClassMirror(cls, type, Bool::False(), Object::null_instance());
   } else if (type.IsTypeParameter()) {
     // TODO(regis): Until mirrors reflect nullability, force kLegacy.
-    const TypeParameter& legacy_type =
-        TypeParameter::Handle(TypeParameter::Cast(type).ToNullability(
-            Nullability::kLegacy, Heap::kOld));
+    const TypeParameter& legacy_type = TypeParameter::Handle(
+        TypeParameter::Cast(type).ToNullability(kLegacy, Heap::kOld));
     return CreateTypeVariableMirror(legacy_type, Object::null_instance());
   }
   UNREACHABLE();

runtime/vm/compiler/frontend/bytecode_reader.cc

@@ -502,12 +502,11 @@ void BytecodeReaderHelper::ReadClosureDeclaration(const Function& function,
   closures_->SetAt(closureIndex, closure);
 
   Type& signature_type = Type::Handle(
-      Z, ReadFunctionSignature(closure,
-                               (flags & kHasOptionalPositionalParamsFlag) != 0,
-                               (flags & kHasOptionalNamedParamsFlag) != 0,
-                               (flags & kHasTypeParamsFlag) != 0,
-                               /* has_positional_param_names = */ true,
-                               Nullability::kNonNullable));
+      Z, ReadFunctionSignature(
+             closure, (flags & kHasOptionalPositionalParamsFlag) != 0,
+             (flags & kHasOptionalNamedParamsFlag) != 0,
+             (flags & kHasTypeParamsFlag) != 0,
+             /* has_positional_param_names = */ true, kNonNullable));
 
   closure.SetSignatureType(signature_type);
 
@@ -1509,7 +1508,7 @@ RawObject* BytecodeReaderHelper::ReadObjectContents(uint32_t header) {
       const Nullability nullability =
           bytecode_component_->GetVersion() >= 24
               ? static_cast<Nullability>((flags & kNullabilityMask) / kFlagBit4)
-              : Nullability::kLegacy;
+              : kLegacy;
       return ReadType(tag, nullability);
     }
     default:

runtime/vm/compiler/frontend/kernel_fingerprints.cc

@@ -246,7 +246,7 @@ void KernelFingerprintHelper::CalculateDartTypeFingerprint() {
       break;
     case kTypeParameterType: {
       Nullability nullability = ReadNullability();
-      BuildHash(static_cast<uint32_t>(nullability));
+      BuildHash(nullability);
       ReadUInt();                              // read index for parameter.
       CalculateOptionalDartTypeFingerprint();  // read bound bound.
       break;
@@ -269,7 +269,7 @@ void KernelFingerprintHelper::CalculateOptionalDartTypeFingerprint() {
 
 void KernelFingerprintHelper::CalculateInterfaceTypeFingerprint(bool simple) {
   Nullability nullability = ReadNullability();
-  BuildHash(static_cast<uint32_t>(nullability));
+  BuildHash(nullability);
   NameIndex kernel_class = ReadCanonicalNameReference();
   ASSERT(H.IsClass(kernel_class));
   const String& class_name = H.DartClassName(kernel_class);
@@ -285,7 +285,7 @@ void KernelFingerprintHelper::CalculateInterfaceTypeFingerprint(bool simple) {
 
 void KernelFingerprintHelper::CalculateFunctionTypeFingerprint(bool simple) {
   Nullability nullability = ReadNullability();
-  BuildHash(static_cast<uint32_t>(nullability));
+  BuildHash(nullability);
 
   if (!simple) {
     CalculateTypeParametersListFingerprint();  // read type_parameters.

runtime/vm/compiler/frontend/kernel_translation_helper.cc

@@ -2768,7 +2768,7 @@ void TypeTranslator::BuildTypeInternal() {
       break;
     case kBottomType:
       result_ = Class::Handle(Z, I->object_store()->null_class())
-                    .DeclarationType(Nullability::kNullable);
+                    .DeclarationType(kNullable);
       ASSERT(result_.IsNullable());
       break;
     case kNeverType:

runtime/vm/object.cc

@@ -944,13 +944,13 @@ void Object::Init(Isolate* isolate) {
   cls.set_is_type_finalized();
 
   cls = dynamic_class_;
-  *dynamic_type_ = Type::NewNonParameterizedType(cls, Nullability::kNullable);
+  *dynamic_type_ = Type::NewNonParameterizedType(cls, kNullable);
 
   cls = void_class_;
-  *void_type_ = Type::NewNonParameterizedType(cls, Nullability::kNullable);
+  *void_type_ = Type::NewNonParameterizedType(cls, kNullable);
 
   cls = never_class_;
-  *never_type_ = Type::NewNonParameterizedType(cls, Nullability::kNonNullable);
+  *never_type_ = Type::NewNonParameterizedType(cls, kNonNullable);
 
   // Since TypeArguments objects are passed as function arguments, make them
   // behave as Dart instances, although they are just VM objects.
@@ -1934,7 +1934,7 @@ RawError* Object::Init(Isolate* isolate,
     // name is a built-in identifier (this is wrong).  The corresponding types
     // are stored in the object store.
     cls = object_store->null_class();
-    type = Type::NewNonParameterizedType(cls, Nullability::kNullable);
+    type = Type::NewNonParameterizedType(cls, kNullable);
     cls.set_declaration_type(type);
     object_store->set_null_type(type);
     ASSERT(type.IsNullable());
@@ -4345,7 +4345,7 @@ RawType* Class::DeclarationType(Nullability nullability) const {
   ASSERT(is_declaration_loaded());
   if (IsNullClass()) {
     // Ignore requested nullability (e.g. by mirrors).
-    nullability = Nullability::kNullable;
+    nullability = kNullable;
   }
   Type& type = Type::Handle(declaration_type());
   if (!type.IsNull()) {
@@ -16664,8 +16664,8 @@ RawAbstractType* Instance::GetType(Heap::Space space) const {
     }
     // TODO(regis): The runtime type of a non-null instance should be
     // non-nullable instead of legacy. Revisit.
-    type = Type::New(cls, type_arguments, TokenPosition::kNoSource,
-                     Nullability::kLegacy, space);
+    type = Type::New(cls, type_arguments, TokenPosition::kNoSource, kLegacy,
+                     space);
     type.SetIsFinalized();
     type ^= type.Canonicalize();
   }
@@ -17019,7 +17019,7 @@ TokenPosition AbstractType::token_pos() const {
 Nullability AbstractType::nullability() const {
   // AbstractType is an abstract class.
   UNREACHABLE();
-  return Nullability::kNullable;
+  return kNullable;
 }
 
 bool AbstractType::IsInstantiated(Genericity genericity,
@@ -17201,21 +17201,8 @@ RawString* AbstractType::PrintURIs(URIs* uris) {
   return Symbols::FromConcatAll(thread, pieces);
 }
 
-static const String& NullabilitySuffix(Nullability value) {
-  // Keep in sync with Nullability enum in runtime/vm/object.h.
-  switch (value) {
-    case Nullability::kUndetermined:
-      return Symbols::Percent();
-    case Nullability::kNullable:
-      return Symbols::QuestionMark();
-    case Nullability::kNonNullable:
-      return Symbols::Empty();
-    case Nullability::kLegacy:
-      return Symbols::Star();
-    default:
-      UNREACHABLE();
-  }
-}
+// Keep in sync with Nullability enum in runtime/vm/object.h.
+static const char* nullability_suffix[4] = {"%", "?", "", "*"};
 
 RawString* AbstractType::BuildName(NameVisibility name_visibility) const {
   ASSERT(name_visibility != kScrubbedName);
@@ -17225,7 +17212,7 @@ RawString* AbstractType::BuildName(NameVisibility name_visibility) const {
     if (FLAG_show_nullability) {
       return Symbols::FromConcat(
           thread, String::Handle(zone, TypeParameter::Cast(*this).name()),
-          NullabilitySuffix(nullability()));
+          String::Handle(zone, String::New(nullability_suffix[nullability()])));
     }
     return TypeParameter::Cast(*this).name();
   }
@@ -17243,7 +17230,8 @@ RawString* AbstractType::BuildName(NameVisibility name_visibility) const {
         return Symbols::FromConcat(
             thread,
             String::Handle(zone, signature_function.UserVisibleSignature()),
-            NullabilitySuffix(nullability()));
+            String::Handle(zone,
+                           String::New(nullability_suffix[nullability()])));
       }
       return signature_function.UserVisibleSignature();
     }
@@ -17253,9 +17241,10 @@ RawString* AbstractType::BuildName(NameVisibility name_visibility) const {
     if (!IsFinalized() || IsBeingFinalized()) {
       // TODO(regis): Check if this is dead code.
       if (FLAG_show_nullability) {
-        return Symbols::FromConcat(thread,
-                                   String::Handle(zone, class_name.raw()),
-                                   NullabilitySuffix(nullability()));
+        return Symbols::FromConcat(
+            thread, String::Handle(zone, class_name.raw()),
+            String::Handle(zone,
+                           String::New(nullability_suffix[nullability()])));
       }
       return class_name.raw();
     }
@@ -17298,7 +17287,8 @@ RawString* AbstractType::BuildName(NameVisibility name_visibility) const {
     pieces.Add(args_name);
   }
   if (FLAG_show_nullability) {
-    pieces.Add(NullabilitySuffix(nullability()));
+    pieces.Add(
+        String::Handle(zone, String::New(nullability_suffix[nullability()])));
   }
   // The name is only used for type checking and debugging purposes.
   // Unless profiling data shows otherwise, it is not worth caching the name in
@@ -17337,7 +17327,7 @@ bool AbstractType::IsTopType(NNBDMode mode) const {
     return false;
   }
   if (cid == kDynamicCid || cid == kVoidCid ||
-      (cid == kInstanceCid && (mode != NNBDMode::kStrong || IsNullable()))) {
+      (cid == kInstanceCid && (mode != kStrong || IsNullable()))) {
     return true;
   }
   // FutureOr<T> where T is a top type behaves as a top type.
@@ -18473,7 +18463,7 @@ void TypeParameter::SetGenericCovariantImpl(bool value) const {
 }
 
 void TypeParameter::set_nullability(Nullability value) const {
-  StoreNonPointer(&raw_ptr()->nullability_, static_cast<int8_t>(value));
+  StoreNonPointer(&raw_ptr()->nullability_, value);
 }
 
 RawTypeParameter* TypeParameter::ToNullability(Nullability value,
@@ -18672,7 +18662,7 @@ RawTypeParameter* TypeParameter::New(const Class& parameterized_class,
   result.set_name(name);
   result.set_bound(bound);
   result.set_flags(0);
-  result.set_nullability(Nullability::kLegacy);
+  result.set_nullability(kLegacy);
   result.SetGenericCovariantImpl(is_generic_covariant_impl);
   result.SetHash(0);
   result.set_token_pos(token_pos);

runtime/vm/object.h

@@ -838,7 +838,7 @@ typedef ZoneGrowableHandlePtrArray<const AbstractType>* TrailPtr;
 typedef ZoneGrowableHandlePtrArray<const String> URIs;
 
 // Keep in sync with package:kernel/lib/ast.dart
-enum class Nullability {
+enum Nullability {
   kUndetermined = 0,
   kNullable = 1,
   kNonNullable = 2,
@@ -846,7 +846,7 @@ enum class Nullability {
 };
 
 // Nullability aware subtype checking modes.
-enum class NNBDMode {
+enum NNBDMode {
   kUnaware,
   kWeak,
   kStrong,
@@ -954,8 +954,7 @@ class Class : public Object {
   // variant may be requested. The first requested type gets cached in the class
   // and subsequent nullability variants get cached in the object store.
   // TODO(regis): Is this caching still useful or should we eliminate it?
-  RawType* DeclarationType(
-      Nullability nullability = Nullability::kLegacy) const;
+  RawType* DeclarationType(Nullability nullability = kLegacy) const;
 
   static intptr_t declaration_type_offset() {
     return OFFSET_OF(RawClass, declaration_type_);
@@ -2190,8 +2189,7 @@ class Function : public Object {
   // function type with uninstantiated type arguments 'T' and 'R' as elements of
   // its type argument vector.
   // A function type is non-nullable by default.
-  RawType* SignatureType(
-      Nullability nullability = Nullability::kNonNullable) const;
+  RawType* SignatureType(Nullability nullability = kNonNullable) const;
   RawType* ExistingSignatureType() const;
 
   // Update the signature type (with a canonical version).
@@ -6821,18 +6819,10 @@ class AbstractType : public Instance {
   virtual void SetIsBeingFinalized() const;
 
   virtual Nullability nullability() const;
-  virtual bool IsUndetermined() const {
-    return nullability() == Nullability::kUndetermined;
-  }
-  virtual bool IsNullable() const {
-    return nullability() == Nullability::kNullable;
-  }
-  virtual bool IsNonNullable() const {
-    return nullability() == Nullability::kNonNullable;
-  }
-  virtual bool IsLegacy() const {
-    return nullability() == Nullability::kLegacy;
-  }
+  virtual bool IsUndetermined() const { return nullability() == kUndetermined; }
+  virtual bool IsNullable() const { return nullability() == kNullable; }
+  virtual bool IsNonNullable() const { return nullability() == kNonNullable; }
+  virtual bool IsLegacy() const { return nullability() == kLegacy; }
 
   virtual bool HasTypeClass() const { return type_class_id() != kIllegalCid; }
   virtual classid_t type_class_id() const;
@@ -6954,7 +6944,7 @@ class AbstractType : public Instance {
 
   // Check if this type represents a top type.
   // TODO(regis): Remove default kUnaware mode as implementation progresses.
-  bool IsTopType(NNBDMode mode = NNBDMode::kUnaware) const;
+  bool IsTopType(NNBDMode mode = kUnaware) const;
 
   // Check if this type represents the 'bool' type.
   bool IsBoolType() const;
@@ -7067,8 +7057,8 @@ class Type : public AbstractType {
   }
   void set_nullability(Nullability value) const {
     ASSERT(!IsCanonical());
-    ASSERT(value != Nullability::kUndetermined);
-    StoreNonPointer(&raw_ptr()->nullability_, static_cast<int8_t>(value));
+    ASSERT(value != kUndetermined);
+    StoreNonPointer(&raw_ptr()->nullability_, value);
   }
   RawType* ToNullability(Nullability value, Heap::Space space) const;
   virtual classid_t type_class_id() const;
@@ -7167,14 +7157,13 @@ class Type : public AbstractType {
   static RawType* DartTypeType();
 
   // The finalized type of the given non-parameterized class.
-  static RawType* NewNonParameterizedType(
-      const Class& type_class,
-      Nullability nullability = Nullability::kLegacy);
+  static RawType* NewNonParameterizedType(const Class& type_class,
+                                          Nullability nullability = kLegacy);
 
   static RawType* New(const Class& clazz,
                       const TypeArguments& arguments,
                       TokenPosition token_pos,
-                      Nullability nullability = Nullability::kLegacy,
+                      Nullability nullability = kLegacy,
                       Heap::Space space = Heap::kOld);
 
  private:

runtime/vm/symbols.h

@@ -580,9 +580,6 @@ class Symbols : public AllStatic {
   static const String& Percent() {
     return *(symbol_handles_[kNullCharId + '%']);
   }
-  static const String& QuestionMark() {
-    return *(symbol_handles_[kNullCharId + '?']);
-  }
   static const String& Caret() { return *(symbol_handles_[kNullCharId + '^']); }
   static const String& Tilde() { return *(symbol_handles_[kNullCharId + '~']); }