[cfe][nnbd] (De)Serialize nullability modifiers in .dill files

Closes #37688.

Bug: http://dartbug.com/37688
Change-Id: Ie3aa8fe09d859cd65bbb58da3f56297483b7b725
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112085
Commit-Queue: Dmitry Stefantsov <[email protected]>
Reviewed-by: Jens Johansen <[email protected]>

Author: Dmitry Stefantsov

pkg/kernel/binary.md

@@ -139,7 +139,7 @@ type CanonicalName {
 
 type ComponentFile {
   UInt32 magic = 0x90ABCDEF;
-  UInt32 formatVersion = 27;
+  UInt32 formatVersion = 28;
   List<String> problemsAsJson; // Described in problems.md.
   Library[] libraries;
   UriSource sourceMap;
@@ -1195,6 +1195,8 @@ type FunctionDeclaration extends Statement {
   FunctionNode function;
 }
 
+enum Nullability { nullable = 0, nonNullable = 1, neither = 2, legacy = 3, }
+
 abstract type DartType extends Node {}
 
 type InvalidType extends DartType {
@@ -1211,18 +1213,21 @@ type VoidType extends DartType {
 
 type InterfaceType extends DartType {
   Byte tag = 93;
+  Byte nullability; // Index into the Nullability enum above.
   ClassReference class;
   List<DartType> typeArguments;
 }
 
 type SimpleInterfaceType extends DartType {
   Byte tag = 96; // Note: tag is out of order.
+  Byte nullability; // Index into the Nullability enum above.
   ClassReference class;
   // Equivalent to InterfaceType with empty list of type arguments.
 }
 
 type FunctionType extends DartType {
   Byte tag = 94;
+  Byte nullability; // Index into the Nullability enum above.
   List<TypeParameter> typeParameters;
   UInt requiredParameterCount;
   // positionalParameters.length + namedParameters.length
@@ -1235,6 +1240,7 @@ type FunctionType extends DartType {
 
 type SimpleFunctionType extends DartType {
   Byte tag = 97; // Note: tag is out of order.
+  Byte nullability; // Index into the Nullability enum above.
   List<DartType> positionalParameters;
   List<StringReference> positionalParameterNames;
   DartType returnType;
@@ -1249,6 +1255,7 @@ type NamedDartType {
 
 type TypeParameterType extends DartType {
   Byte tag = 95;
+  Byte nullability; // Index into the Nullability enum above.
 
   // Reference to the Nth type parameter in scope (with some caveats about
   // type parameter bounds).
@@ -1273,6 +1280,7 @@ type TypeParameterType extends DartType {
 
 type TypedefType {
   Byte tag = 87;
+  Byte nullability; // Index into the Nullability enum above.
   TypedefReference typedefReference;
   List<DartType> typeArguments;
 }

pkg/kernel/lib/ast.dart

@@ -4819,12 +4819,6 @@ class _PublicName extends Name {
 
 /// Represents nullability of a type.
 enum Nullability {
-  /// Types in opt-out libraries are 'legacy' types.
-  ///
-  /// They are both subtypes and supertypes of the nullable and non-nullable
-  /// versions of the type.
-  legacy,
-
   /// Nullable types are marked with the '?' modifier.
   ///
   /// Null, dynamic, and void are nullable by default.
@@ -4849,7 +4843,13 @@ enum Nullability {
   ///       Object y = x;  // Compile-time error.
   ///     }
   ///   }
-  neither
+  neither,
+
+  /// Types in opt-out libraries are 'legacy' types.
+  ///
+  /// They are both subtypes and supertypes of the nullable and non-nullable
+  /// versions of the type.
+  legacy
 }
 
 /// A syntax-independent notion of a type.
@@ -5271,7 +5271,7 @@ class TypeParameterType extends DartType {
   DartType promotedBound;
 
   TypeParameterType(this.parameter,
-      [this.promotedBound, this.declaredNullability])
+      [this.promotedBound, this.declaredNullability = Nullability.legacy])
       : this.nullability =
             getNullability(parameter, promotedBound, declaredNullability);
 

pkg/kernel/lib/binary/ast_from_binary.dart

@@ -1961,8 +1961,9 @@ class BinaryBuilder {
     int tag = readByte();
     switch (tag) {
       case Tag.TypedefType:
-        return new TypedefType.byReference(
-            readTypedefReference(), readDartTypeList());
+        int nullabilityIndex = readByte();
+        return new TypedefType.byReference(readTypedefReference(),
+            readDartTypeList(), Nullability.values[nullabilityIndex]);
       case Tag.BottomType:
         return const BottomType();
       case Tag.InvalidType:
@@ -1972,13 +1973,16 @@ class BinaryBuilder {
       case Tag.VoidType:
         return const VoidType();
       case Tag.InterfaceType:
-        return new InterfaceType.byReference(
-            readClassReference(), readDartTypeList());
+        int nullabilityIndex = readByte();
+        return new InterfaceType.byReference(readClassReference(),
+            readDartTypeList(), Nullability.values[nullabilityIndex]);
       case Tag.SimpleInterfaceType:
-        return new InterfaceType.byReference(
-            readClassReference(), const <DartType>[]);
+        int nullabilityIndex = readByte();
+        return new InterfaceType.byReference(readClassReference(),
+            const <DartType>[], Nullability.values[nullabilityIndex]);
       case Tag.FunctionType:
         int typeParameterStackHeight = typeParameterStack.length;
+        int nullabilityIndex = readByte();
         var typeParameters = readAndPushTypeParameterList();
         var requiredParameterCount = readUInt();
         var totalParameterCount = readUInt();
@@ -1992,15 +1996,20 @@ class BinaryBuilder {
             typeParameters: typeParameters,
             requiredParameterCount: requiredParameterCount,
             namedParameters: named,
-            typedefType: typedefType);
+            typedefType: typedefType,
+            nullability: Nullability.values[nullabilityIndex]);
       case Tag.SimpleFunctionType:
+        int nullabilityIndex = readByte();
         var positional = readDartTypeList();
         var returnType = readDartType();
-        return new FunctionType(positional, returnType);
+        return new FunctionType(positional, returnType,
+            nullability: Nullability.values[nullabilityIndex]);
       case Tag.TypeParameterType:
+        int declaredNullabilityIndex = readByte();
         int index = readUInt();
         var bound = readDartTypeOption();
-        return new TypeParameterType(typeParameterStack[index], bound);
+        return new TypeParameterType(typeParameterStack[index], bound,
+            Nullability.values[declaredNullabilityIndex]);
       default:
         throw fail('unexpected dart type tag: $tag');
     }

pkg/kernel/lib/binary/ast_to_binary.dart

@@ -2006,21 +2006,29 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
   void visitInterfaceType(InterfaceType node) {
     if (node.typeArguments.isEmpty) {
       writeByte(Tag.SimpleInterfaceType);
+      writeByte(node.nullability.index);
       writeNonNullReference(node.className);
     } else {
       writeByte(Tag.InterfaceType);
+      writeByte(node.nullability.index);
       writeNonNullReference(node.className);
       writeNodeList(node.typeArguments);
     }
   }
 
   @override
   void visitSupertype(Supertype node) {
+    // Writing nullability below is only necessary because
+    // BinaryBuilder.readSupertype reads the supertype as an InterfaceType and
+    // breaks it into components afterwards, and reading an InterfaceType
+    // requires the nullability byte.
     if (node.typeArguments.isEmpty) {
       writeByte(Tag.SimpleInterfaceType);
+      writeByte(Nullability.nonNullable.index);
       writeNonNullReference(node.className);
     } else {
       writeByte(Tag.InterfaceType);
+      writeByte(Nullability.nonNullable.index);
       writeNonNullReference(node.className);
       writeNodeList(node.typeArguments);
     }
@@ -2033,10 +2041,12 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
         node.namedParameters.isEmpty &&
         node.typedefType == null) {
       writeByte(Tag.SimpleFunctionType);
+      writeByte(node.nullability.index);
       writeNodeList(node.positionalParameters);
       writeNode(node.returnType);
     } else {
       writeByte(Tag.FunctionType);
+      writeByte(node.nullability.index);
       enterScope(typeParameters: node.typeParameters);
       writeNodeList(node.typeParameters);
       writeUInt30(node.requiredParameterCount);
@@ -2059,13 +2069,15 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
   @override
   void visitTypeParameterType(TypeParameterType node) {
     writeByte(Tag.TypeParameterType);
+    writeByte(node.declaredNullability.index);
     writeUInt30(_typeParameterIndexer[node.parameter]);
     writeOptionalNode(node.promotedBound);
   }
 
   @override
   void visitTypedefType(TypedefType node) {
     writeByte(Tag.TypedefType);
+    writeByte(node.nullability.index);
     writeNullAllowedReference(node.typedefReference);
     writeNodeList(node.typeArguments);
   }

pkg/kernel/lib/binary/tag.dart

@@ -150,7 +150,7 @@ class Tag {
   /// Internal version of kernel binary format.
   /// Bump it when making incompatible changes in kernel binaries.
   /// Keep in sync with runtime/vm/kernel_binary.h, pkg/kernel/binary.md.
-  static const int BinaryFormatVersion = 27;
+  static const int BinaryFormatVersion = 28;
 }
 
 abstract class ConstantTag {

runtime/vm/compiler/frontend/kernel_binary_flowgraph.cc

@@ -1310,6 +1310,13 @@ Tag KernelReaderHelper::PeekTag(uint8_t* payload) {
   return reader_.PeekTag(payload);
 }
 
+Nullability KernelReaderHelper::ReadNullability() {
+  if (translation_helper_.info().kernel_binary_version() >= 28) {
+    return reader_.ReadNullability();
+  }
+  return kLegacy;
+}
+
 void StreamingFlowGraphBuilder::loop_depth_inc() {
   ++flow_graph_builder_->loop_depth_;
 }

runtime/vm/compiler/frontend/kernel_fingerprints.cc

@@ -239,10 +239,13 @@ void KernelFingerprintHelper::CalculateDartTypeFingerprint() {
     case kSimpleFunctionType:
       CalculateFunctionTypeFingerprint(true);
       break;
-    case kTypeParameterType:
+    case kTypeParameterType: {
+      Nullability nullability = ReadNullability();
+      BuildHash(nullability);
       ReadUInt();                              // read index for parameter.
       CalculateOptionalDartTypeFingerprint();  // read bound bound.
       break;
+    }
     default:
       ReportUnexpectedTag("type", tag);
       UNREACHABLE();
@@ -260,6 +263,8 @@ void KernelFingerprintHelper::CalculateOptionalDartTypeFingerprint() {
 }
 
 void KernelFingerprintHelper::CalculateInterfaceTypeFingerprint(bool simple) {
+  Nullability nullability = ReadNullability();
+  BuildHash(nullability);
   NameIndex kernel_class = ReadCanonicalNameReference();
   ASSERT(H.IsClass(kernel_class));
   const String& class_name = H.DartClassName(kernel_class);
@@ -274,6 +279,9 @@ void KernelFingerprintHelper::CalculateInterfaceTypeFingerprint(bool simple) {
 }
 
 void KernelFingerprintHelper::CalculateFunctionTypeFingerprint(bool simple) {
+  Nullability nullability = ReadNullability();
+  BuildHash(nullability);
+
   if (!simple) {
     CalculateTypeParametersListFingerprint();  // read type_parameters.
     BuildHash(ReadUInt());                     // read required parameter count.

runtime/vm/compiler/frontend/kernel_translation_helper.cc

@@ -1983,10 +1983,12 @@ void KernelReaderHelper::SkipDartType() {
       SkipFunctionType(true);
       return;
     case kTypedefType:
+      ReadNullability();      // read nullability.
       ReadUInt();             // read index for canonical name.
       SkipListOfDartTypes();  // read list of types.
       return;
     case kTypeParameterType:
+      ReadNullability();       // read nullability.
       ReadUInt();              // read index for parameter.
       SkipOptionalDartType();  // read bound bound.
       return;
@@ -2007,13 +2009,16 @@ void KernelReaderHelper::SkipOptionalDartType() {
 }
 
 void KernelReaderHelper::SkipInterfaceType(bool simple) {
+  ReadNullability();  // read nullability.
   ReadUInt();  // read klass_name.
   if (!simple) {
     SkipListOfDartTypes();  // read list of types.
   }
 }
 
 void KernelReaderHelper::SkipFunctionType(bool simple) {
+  ReadNullability();  // read nullability.
+
   if (!simple) {
     SkipTypeParametersList();  // read type_parameters.
     ReadUInt();                // read required parameter count.
@@ -2793,6 +2798,8 @@ void TypeTranslator::BuildInterfaceType(bool simple) {
   // malformed iff `T` is malformed.
   //   => We therefore ignore errors in `A` or `B`.
 
+  helper_->ReadNullability();  // read nullability.
+
   NameIndex klass_name =
       helper_->ReadCanonicalNameReference();  // read klass_name.
 
@@ -2830,6 +2837,8 @@ void TypeTranslator::BuildFunctionType(bool simple) {
                                             : Function::Handle(Z),
                                         TokenPosition::kNoSource));
 
+  helper_->ReadNullability();  // read nullability.
+
   // Suspend finalization of types inside this one. They will be finalized after
   // the whole function type is constructed.
   //
@@ -2920,6 +2929,7 @@ void TypeTranslator::BuildFunctionType(bool simple) {
 }
 
 void TypeTranslator::BuildTypeParameterType() {
+  helper_->ReadNullability();                      // read nullability.
   intptr_t parameter_index = helper_->ReadUInt();  // read parameter index.
   helper_->SkipOptionalDartType();                 // read bound.
 

runtime/vm/compiler/frontend/kernel_translation_helper.h

@@ -1082,6 +1082,7 @@ class KernelReaderHelper {
   TokenPosition ReadPosition(bool record = true);
   Tag ReadTag(uint8_t* payload = NULL);
   uint8_t ReadFlags() { return reader_.ReadFlags(); }
+  Nullability ReadNullability();
 
   intptr_t SourceTableSize();
   intptr_t GetOffsetForSourceInfo(intptr_t index);

runtime/vm/compiler/frontend/scope_builder.cc

@@ -1318,6 +1318,7 @@ void ScopeBuilder::VisitDartType() {
 }
 
 void ScopeBuilder::VisitInterfaceType(bool simple) {
+  helper_.ReadNullability();  // read nullability.
   helper_.ReadUInt();  // read klass_name.
   if (!simple) {
     intptr_t length = helper_.ReadListLength();  // read number of types.
@@ -1328,6 +1329,8 @@ void ScopeBuilder::VisitInterfaceType(bool simple) {
 }
 
 void ScopeBuilder::VisitFunctionType(bool simple) {
+  helper_.ReadNullability();  // read nullability.
+
   if (!simple) {
     intptr_t list_length =
         helper_.ReadListLength();  // read type_parameters list length.
@@ -1375,6 +1378,8 @@ void ScopeBuilder::VisitTypeParameterType() {
     function = function.parent_function();
   }
 
+  helper_.ReadNullability();  // read nullability.
+
   // The index here is the index identifying the type parameter binding site
   // inside the DILL file, which uses a different indexing system than the VM
   // uses for its 'TypeParameter's internally. This index includes both class