pkg/dart2wasm/lib/class_info.dart - sdk.git - Git at Google

 // Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 import 'dart:math';

 import 'package:dart2wasm/translator.dart';

 import 'package:kernel/ast.dart';

 import 'package:wasm_builder/wasm_builder.dart' as w;

 /// Wasm struct field indices for fields that are accessed explicitly from Wasm
 /// code, e.g. in intrinsics.
 ///
 /// The values are validated by asserts, typically either through
 /// [ClassInfo.addField] (for manually added fields) or by a line in
 /// [FieldIndex.validate] (for fields declared in Dart code).
 class FieldIndex {
   static const classId = 0;
   static const boxValue = 1;
   static const identityHash = 1;
   static const stringArray = 2;
   static const hashBaseIndex = 2;
   static const hashBaseData = 4;
   static const closureContext = 2;
   static const closureFunction = 3;
   static const typedListBaseLength = 2;
   static const typedListArray = 3;
   static const typedListViewTypedData = 3;
   static const typedListViewOffsetInBytes = 4;
   static const byteDataViewLength = 2;
   static const byteDataViewTypedData = 3;
   static const byteDataViewOffsetInBytes = 4;

   static void validate(Translator translator) {
     void check(Class cls, String name, int expectedIndex) {
       assert(
           translator.fieldIndex[
                   cls.fields.firstWhere((f) => f.name.text == name)] ==
               expectedIndex,
           "Unexpected field index for ${cls.name}.$name");
     }

     check(translator.boxedBoolClass, "value", FieldIndex.boxValue);
     check(translator.boxedIntClass, "value", FieldIndex.boxValue);
     check(translator.boxedDoubleClass, "value", FieldIndex.boxValue);
     check(translator.oneByteStringClass, "_array", FieldIndex.stringArray);
     check(translator.twoByteStringClass, "_array", FieldIndex.stringArray);
     check(translator.hashFieldBaseClass, "_index", FieldIndex.hashBaseIndex);
     check(translator.hashFieldBaseClass, "_data", FieldIndex.hashBaseData);
     check(translator.functionClass, "context", FieldIndex.closureContext);
   }
 }

 const int initialIdentityHash = 0;

 /// Information about the Wasm representation for a class.
 class ClassInfo {
   /// The Dart class that this info corresponds to. The top type does not have
   /// an associated Dart class.
   final Class? cls;

   /// The Class ID of this class, stored in every instance of the class.
   final int classId;

   /// Depth of this class in the Wasm type hierarchy.
   final int depth;

   /// The Wasm struct used to represent instances of this class. A class will
   /// sometimes use the same struct as its superclass.
   final w.StructType struct;

   /// Wasm global containing the RTT for this class.
   late final w.DefinedGlobal rtt;

   /// The superclass for this class. This will usually be the Dart superclass,
   /// but there are a few exceptions, where the Wasm type hierarchy does not
   /// follow the Dart class hierarchy.
   final ClassInfo? superInfo;

   /// For every type parameter which is directly mapped to a type parameter in
   /// the superclass, this contains the corresponding superclass type
   /// parameter. These will reuse the corresponding type parameter field of
   /// the superclass.
   final Map<TypeParameter, TypeParameter> typeParameterMatch;

   /// The class whose struct is used as the type for variables of this type.
   /// This is a type which is a superclass of all subtypes of this type.
   late ClassInfo repr;

   /// All classes which implement this class. This is used to compute `repr`.
   final List<ClassInfo> implementedBy = [];

   late final w.RefType nullableType = w.RefType.def(struct, nullable: true);
   late final w.RefType nonNullableType = w.RefType.def(struct, nullable: false);

   w.RefType typeWithNullability(bool nullable) =>
       nullable ? nullableType : nonNullableType;

   ClassInfo(this.cls, this.classId, this.depth, this.struct, this.superInfo,
       ClassInfoCollector collector,
       {this.typeParameterMatch = const {}}) {
     if (collector.options.useRttGlobals) {
       rtt = collector.makeRtt(struct, superInfo);
     }
     implementedBy.add(this);
   }

   void addField(w.FieldType fieldType, [int? expectedIndex]) {
     assert(expectedIndex == null || expectedIndex == struct.fields.length);
     struct.fields.add(fieldType);
   }
 }

 ClassInfo upperBound(Iterable<ClassInfo> classes) {
   while (classes.length > 1) {
     Set<ClassInfo> newClasses = {};
     int minDepth = 999999999;
     int maxDepth = 0;
     for (ClassInfo info in classes) {
       minDepth = min(minDepth, info.depth);
       maxDepth = max(maxDepth, info.depth);
     }
     int targetDepth = minDepth == maxDepth ? minDepth - 1 : minDepth;
     for (ClassInfo info in classes) {
       while (info.depth > targetDepth) {
         info = info.superInfo!;
       }
       newClasses.add(info);
     }
     classes = newClasses;
   }
   return classes.single;
 }

 /// Constructs the Wasm type hierarchy.
 class ClassInfoCollector {
   final Translator translator;
   int nextClassId = 0;
   late final ClassInfo topInfo;

   late final w.FieldType typeType =
       w.FieldType(translator.classInfo[translator.typeClass]!.nullableType);

   ClassInfoCollector(this.translator);

   w.Module get m => translator.m;

   TranslatorOptions get options => translator.options;

   w.DefinedGlobal makeRtt(w.StructType struct, ClassInfo? superInfo) {
     assert(options.useRttGlobals);
     int depth = superInfo != null ? superInfo.depth + 1 : 0;
     final w.DefinedGlobal rtt =
         m.addGlobal(w.GlobalType(w.Rtt(struct, depth), mutable: false));
     final w.Instructions b = rtt.initializer;
     if (superInfo != null) {
       b.global_get(superInfo.rtt);
       b.rtt_sub(struct);
     } else {
       b.rtt_canon(struct);
     }
     b.end();
     return rtt;
   }

   void initializeTop() {
     final w.StructType struct = translator.structType("#Top");
     topInfo = ClassInfo(null, nextClassId++, 0, struct, null, this);
     translator.classes.add(topInfo);
     translator.classForHeapType[struct] = topInfo;
   }

   void initialize(Class cls) {
     ClassInfo? info = translator.classInfo[cls];
     if (info == null) {
       Class? superclass = cls.superclass;
       if (superclass == null) {
         ClassInfo superInfo = topInfo;
         final w.StructType struct =
             translator.structType(cls.name, superType: superInfo.struct);
         info = ClassInfo(
             cls, nextClassId++, superInfo.depth + 1, struct, superInfo, this);
         // Mark Top type as implementing Object to force the representation
         // type of Object to be Top.
         info.implementedBy.add(topInfo);
       } else {
         // Recursively initialize all supertypes before initializing this class.
         initialize(superclass);
         for (Supertype interface in cls.implementedTypes) {
           initialize(interface.classNode);
         }

         // In the Wasm type hierarchy, Object, bool and num sit directly below
         // the Top type. The implementation classes (_StringBase, _Type and the
         // box classes) sit directly below the public classes they implement.
         // All other classes sit below their superclass.
         ClassInfo superInfo = cls == translator.coreTypes.boolClass ||
                 cls == translator.coreTypes.numClass
             ? topInfo
             : cls == translator.stringBaseClass ||
                     cls == translator.typeClass ||
                     translator.boxedClasses.values.contains(cls)
                 ? translator.classInfo[cls.implementedTypes.single.classNode]!
                 : translator.classInfo[superclass]!;

         // Figure out which type parameters can reuse a type parameter field of
         // the superclass.
         Map<TypeParameter, TypeParameter> typeParameterMatch = {};
         if (cls.typeParameters.isNotEmpty) {
           Supertype supertype = cls.superclass == superInfo.cls
               ? cls.supertype!
               : cls.implementedTypes.single;
           for (TypeParameter parameter in cls.typeParameters) {
             for (int i = 0; i < supertype.typeArguments.length; i++) {
               DartType arg = supertype.typeArguments[i];
               if (arg is TypeParameterType && arg.parameter == parameter) {
                 typeParameterMatch[parameter] =
                     superInfo.cls!.typeParameters[i];
                 break;
               }
             }
           }
         }

         // A class can reuse the Wasm struct of the superclass if it doesn't
         // declare any Wasm fields of its own. This is the case when three
         // conditions are met:
         //   1. All type parameters can reuse a type parameter field of the
         //      superclass.
         //   2. The class declares no Dart fields of its own.
         //   3. The class is not a special class that contains hidden fields.
         bool canReuseSuperStruct =
             typeParameterMatch.length == cls.typeParameters.length &&
                 cls.fields.where((f) => f.isInstanceMember).isEmpty &&
                 cls != translator.typedListBaseClass &&
                 cls != translator.typedListClass &&
                 cls != translator.typedListViewClass &&
                 cls != translator.byteDataViewClass;
         w.StructType struct = canReuseSuperStruct
             ? superInfo.struct
             : translator.structType(cls.name, superType: superInfo.struct);
         info = ClassInfo(
             cls, nextClassId++, superInfo.depth + 1, struct, superInfo, this,
             typeParameterMatch: typeParameterMatch);

         // Mark all interfaces as being implemented by this class. This is
         // needed to calculate representation types.
         for (Supertype interface in cls.implementedTypes) {
           ClassInfo? interfaceInfo = translator.classInfo[interface.classNode];
           while (interfaceInfo != null) {
             interfaceInfo.implementedBy.add(info);
             interfaceInfo = interfaceInfo.superInfo;
           }
         }
       }
       translator.classes.add(info);
       translator.classInfo[cls] = info;
       translator.classForHeapType.putIfAbsent(info.struct, () => info!);
     }
   }

   void computeRepresentation(ClassInfo info) {
     info.repr = upperBound(info.implementedBy);
   }

   void generateFields(ClassInfo info) {
     ClassInfo? superInfo = info.superInfo;
     if (superInfo == null) {
       // Top - add class id field
       info.addField(w.FieldType(w.NumType.i32), FieldIndex.classId);
     } else if (info.struct != superInfo.struct) {
       // Copy fields from superclass
       for (w.FieldType fieldType in superInfo.struct.fields) {
         info.addField(fieldType);
       }
       if (info.cls!.superclass == null) {
         // Object - add identity hash code field
         info.addField(w.FieldType(w.NumType.i32), FieldIndex.identityHash);
       }
       // Add fields for type variables
       for (TypeParameter parameter in info.cls!.typeParameters) {
         TypeParameter? match = info.typeParameterMatch[parameter];
         if (match != null) {
           // Reuse supertype type variable
           translator.typeParameterIndex[parameter] =
               translator.typeParameterIndex[match]!;
         } else {
           translator.typeParameterIndex[parameter] = info.struct.fields.length;
           info.addField(typeType);
         }
       }
       // Add fields for Dart instance fields
       for (Field field in info.cls!.fields) {
         if (field.isInstanceMember) {
           w.ValueType wasmType = translator.translateType(field.type);
           // TODO(askesc): Generalize this check for finer nullability control
           if (wasmType != w.RefType.data()) {
             wasmType = wasmType.withNullability(true);
           }
           translator.fieldIndex[field] = info.struct.fields.length;
           info.addField(w.FieldType(wasmType));
         }
       }
     } else {
       for (TypeParameter parameter in info.cls!.typeParameters) {
         // Reuse supertype type variable
         translator.typeParameterIndex[parameter] =
             translator.typeParameterIndex[info.typeParameterMatch[parameter]]!;
       }
     }
   }

   void collect() {
     // Create class info and Wasm structs for all classes.
     initializeTop();
     // Subclasses of the [_Function] class are generated on the fly as fields
     // with function types are encountered. Therefore, this class must be early
     // in the initialization order.
     initialize(translator.functionClass);
     for (Library library in translator.component.libraries) {
       for (Class cls in library.classes) {
         initialize(cls);
       }
     }

     // For each class, compute which Wasm struct should be used for the type of
     // variables bearing that class as their Dart type. This is the struct
     // corresponding to the least common supertype of all Dart classes
     // implementing this class.
     for (ClassInfo info in translator.classes) {
       computeRepresentation(info);
     }

     // Now that the representation types for all classes have been computed,
     // fill in the types of the fields in the generated Wasm structs.
     for (ClassInfo info in translator.classes) {
       generateFields(info);
     }

     // Add hidden fields of typed_data classes.
     addTypedDataFields();

     // Validate that all internally used fields have the expected indices.
     FieldIndex.validate(translator);
   }

   void addTypedDataFields() {
     ClassInfo typedListBaseInfo =
         translator.classInfo[translator.typedListBaseClass]!;
     typedListBaseInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
         FieldIndex.typedListBaseLength);

     ClassInfo typedListInfo = translator.classInfo[translator.typedListClass]!;
     typedListInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
         FieldIndex.typedListBaseLength);
     w.RefType bytesArrayType = w.RefType.def(
         translator.wasmArrayType(w.PackedType.i8, "i8"),
         nullable: false);
     typedListInfo.addField(
         w.FieldType(bytesArrayType, mutable: false), FieldIndex.typedListArray);

     w.RefType typedListType =
         w.RefType.def(typedListInfo.struct, nullable: false);

     ClassInfo typedListViewInfo =
         translator.classInfo[translator.typedListViewClass]!;
     typedListViewInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
         FieldIndex.typedListBaseLength);
     typedListViewInfo.addField(w.FieldType(typedListType, mutable: false),
         FieldIndex.typedListViewTypedData);
     typedListViewInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
         FieldIndex.typedListViewOffsetInBytes);

     ClassInfo byteDataViewInfo =
         translator.classInfo[translator.byteDataViewClass]!;
     byteDataViewInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
         FieldIndex.byteDataViewLength);
     byteDataViewInfo.addField(w.FieldType(typedListType, mutable: false),
         FieldIndex.byteDataViewTypedData);
     byteDataViewInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
         FieldIndex.byteDataViewOffsetInBytes);
   }
 }
	// Copyright (c) 2022, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	import 'dart:math';

	import 'package:dart2wasm/translator.dart';

	import 'package:kernel/ast.dart';

	import 'package:wasm_builder/wasm_builder.dart' as w;

	/// Wasm struct field indices for fields that are accessed explicitly from Wasm
	/// code, e.g. in intrinsics.
	///
	/// The values are validated by asserts, typically either through
	/// [ClassInfo.addField] (for manually added fields) or by a line in
	/// [FieldIndex.validate] (for fields declared in Dart code).
	class FieldIndex {
	static const classId = 0;
	static const boxValue = 1;
	static const identityHash = 1;
	static const stringArray = 2;
	static const hashBaseIndex = 2;
	static const hashBaseData = 4;
	static const closureContext = 2;
	static const closureFunction = 3;
	static const typedListBaseLength = 2;
	static const typedListArray = 3;
	static const typedListViewTypedData = 3;
	static const typedListViewOffsetInBytes = 4;
	static const byteDataViewLength = 2;
	static const byteDataViewTypedData = 3;
	static const byteDataViewOffsetInBytes = 4;

	static void validate(Translator translator) {
	void check(Class cls, String name, int expectedIndex) {
	assert(
	translator.fieldIndex[
	cls.fields.firstWhere((f) => f.name.text == name)] ==
	expectedIndex,
	"Unexpected field index for ${cls.name}.$name");
	}

	check(translator.boxedBoolClass, "value", FieldIndex.boxValue);
	check(translator.boxedIntClass, "value", FieldIndex.boxValue);
	check(translator.boxedDoubleClass, "value", FieldIndex.boxValue);
	check(translator.oneByteStringClass, "_array", FieldIndex.stringArray);
	check(translator.twoByteStringClass, "_array", FieldIndex.stringArray);
	check(translator.hashFieldBaseClass, "_index", FieldIndex.hashBaseIndex);
	check(translator.hashFieldBaseClass, "_data", FieldIndex.hashBaseData);
	check(translator.functionClass, "context", FieldIndex.closureContext);
	}
	}

	const int initialIdentityHash = 0;

	/// Information about the Wasm representation for a class.
	class ClassInfo {
	/// The Dart class that this info corresponds to. The top type does not have
	/// an associated Dart class.
	final Class? cls;

	/// The Class ID of this class, stored in every instance of the class.
	final int classId;

	/// Depth of this class in the Wasm type hierarchy.
	final int depth;

	/// The Wasm struct used to represent instances of this class. A class will
	/// sometimes use the same struct as its superclass.
	final w.StructType struct;

	/// Wasm global containing the RTT for this class.
	late final w.DefinedGlobal rtt;

	/// The superclass for this class. This will usually be the Dart superclass,
	/// but there are a few exceptions, where the Wasm type hierarchy does not
	/// follow the Dart class hierarchy.
	final ClassInfo? superInfo;

	/// For every type parameter which is directly mapped to a type parameter in
	/// the superclass, this contains the corresponding superclass type
	/// parameter. These will reuse the corresponding type parameter field of
	/// the superclass.
	final Map<TypeParameter, TypeParameter> typeParameterMatch;

	/// The class whose struct is used as the type for variables of this type.
	/// This is a type which is a superclass of all subtypes of this type.
	late ClassInfo repr;

	/// All classes which implement this class. This is used to compute `repr`.
	final List<ClassInfo> implementedBy = [];

	late final w.RefType nullableType = w.RefType.def(struct, nullable: true);
	late final w.RefType nonNullableType = w.RefType.def(struct, nullable: false);

	w.RefType typeWithNullability(bool nullable) =>
	nullable ? nullableType : nonNullableType;

	ClassInfo(this.cls, this.classId, this.depth, this.struct, this.superInfo,
	ClassInfoCollector collector,
	{this.typeParameterMatch = const {}}) {
	if (collector.options.useRttGlobals) {
	rtt = collector.makeRtt(struct, superInfo);
	}
	implementedBy.add(this);
	}

	void addField(w.FieldType fieldType, [int? expectedIndex]) {
	assert(expectedIndex == null \|\| expectedIndex == struct.fields.length);
	struct.fields.add(fieldType);
	}
	}

	ClassInfo upperBound(Iterable<ClassInfo> classes) {
	while (classes.length > 1) {
	Set<ClassInfo> newClasses = {};
	int minDepth = 999999999;
	int maxDepth = 0;
	for (ClassInfo info in classes) {
	minDepth = min(minDepth, info.depth);
	maxDepth = max(maxDepth, info.depth);
	}
	int targetDepth = minDepth == maxDepth ? minDepth - 1 : minDepth;
	for (ClassInfo info in classes) {
	while (info.depth > targetDepth) {
	info = info.superInfo!;
	}
	newClasses.add(info);
	}
	classes = newClasses;
	}
	return classes.single;
	}

	/// Constructs the Wasm type hierarchy.
	class ClassInfoCollector {
	final Translator translator;
	int nextClassId = 0;
	late final ClassInfo topInfo;

	late final w.FieldType typeType =
	w.FieldType(translator.classInfo[translator.typeClass]!.nullableType);

	ClassInfoCollector(this.translator);

	w.Module get m => translator.m;

	TranslatorOptions get options => translator.options;

	w.DefinedGlobal makeRtt(w.StructType struct, ClassInfo? superInfo) {
	assert(options.useRttGlobals);
	int depth = superInfo != null ? superInfo.depth + 1 : 0;
	final w.DefinedGlobal rtt =
	m.addGlobal(w.GlobalType(w.Rtt(struct, depth), mutable: false));
	final w.Instructions b = rtt.initializer;
	if (superInfo != null) {
	b.global_get(superInfo.rtt);
	b.rtt_sub(struct);
	} else {
	b.rtt_canon(struct);
	}
	b.end();
	return rtt;
	}

	void initializeTop() {
	final w.StructType struct = translator.structType("#Top");
	topInfo = ClassInfo(null, nextClassId++, 0, struct, null, this);
	translator.classes.add(topInfo);
	translator.classForHeapType[struct] = topInfo;
	}

	void initialize(Class cls) {
	ClassInfo? info = translator.classInfo[cls];
	if (info == null) {
	Class? superclass = cls.superclass;
	if (superclass == null) {
	ClassInfo superInfo = topInfo;
	final w.StructType struct =
	translator.structType(cls.name, superType: superInfo.struct);
	info = ClassInfo(
	cls, nextClassId++, superInfo.depth + 1, struct, superInfo, this);
	// Mark Top type as implementing Object to force the representation
	// type of Object to be Top.
	info.implementedBy.add(topInfo);
	} else {
	// Recursively initialize all supertypes before initializing this class.
	initialize(superclass);
	for (Supertype interface in cls.implementedTypes) {
	initialize(interface.classNode);
	}

	// In the Wasm type hierarchy, Object, bool and num sit directly below
	// the Top type. The implementation classes (_StringBase, _Type and the
	// box classes) sit directly below the public classes they implement.
	// All other classes sit below their superclass.
	ClassInfo superInfo = cls == translator.coreTypes.boolClass \|\|
	cls == translator.coreTypes.numClass
	? topInfo
	: cls == translator.stringBaseClass \|\|
	cls == translator.typeClass \|\|
	translator.boxedClasses.values.contains(cls)
	? translator.classInfo[cls.implementedTypes.single.classNode]!
	: translator.classInfo[superclass]!;

	// Figure out which type parameters can reuse a type parameter field of
	// the superclass.
	Map<TypeParameter, TypeParameter> typeParameterMatch = {};
	if (cls.typeParameters.isNotEmpty) {
	Supertype supertype = cls.superclass == superInfo.cls
	? cls.supertype!
	: cls.implementedTypes.single;
	for (TypeParameter parameter in cls.typeParameters) {
	for (int i = 0; i < supertype.typeArguments.length; i++) {
	DartType arg = supertype.typeArguments[i];
	if (arg is TypeParameterType && arg.parameter == parameter) {
	typeParameterMatch[parameter] =
	superInfo.cls!.typeParameters[i];
	break;
	}
	}
	}
	}

	// A class can reuse the Wasm struct of the superclass if it doesn't
	// declare any Wasm fields of its own. This is the case when three
	// conditions are met:
	// 1. All type parameters can reuse a type parameter field of the
	// superclass.
	// 2. The class declares no Dart fields of its own.
	// 3. The class is not a special class that contains hidden fields.
	bool canReuseSuperStruct =
	typeParameterMatch.length == cls.typeParameters.length &&
	cls.fields.where((f) => f.isInstanceMember).isEmpty &&
	cls != translator.typedListBaseClass &&
	cls != translator.typedListClass &&
	cls != translator.typedListViewClass &&
	cls != translator.byteDataViewClass;
	w.StructType struct = canReuseSuperStruct
	? superInfo.struct
	: translator.structType(cls.name, superType: superInfo.struct);
	info = ClassInfo(
	cls, nextClassId++, superInfo.depth + 1, struct, superInfo, this,
	typeParameterMatch: typeParameterMatch);

	// Mark all interfaces as being implemented by this class. This is
	// needed to calculate representation types.
	for (Supertype interface in cls.implementedTypes) {
	ClassInfo? interfaceInfo = translator.classInfo[interface.classNode];
	while (interfaceInfo != null) {
	interfaceInfo.implementedBy.add(info);
	interfaceInfo = interfaceInfo.superInfo;
	}
	}
	}
	translator.classes.add(info);
	translator.classInfo[cls] = info;
	translator.classForHeapType.putIfAbsent(info.struct, () => info!);
	}
	}

	void computeRepresentation(ClassInfo info) {
	info.repr = upperBound(info.implementedBy);
	}

	void generateFields(ClassInfo info) {
	ClassInfo? superInfo = info.superInfo;
	if (superInfo == null) {
	// Top - add class id field
	info.addField(w.FieldType(w.NumType.i32), FieldIndex.classId);
	} else if (info.struct != superInfo.struct) {
	// Copy fields from superclass
	for (w.FieldType fieldType in superInfo.struct.fields) {
	info.addField(fieldType);
	}
	if (info.cls!.superclass == null) {
	// Object - add identity hash code field
	info.addField(w.FieldType(w.NumType.i32), FieldIndex.identityHash);
	}
	// Add fields for type variables
	for (TypeParameter parameter in info.cls!.typeParameters) {
	TypeParameter? match = info.typeParameterMatch[parameter];
	if (match != null) {
	// Reuse supertype type variable
	translator.typeParameterIndex[parameter] =
	translator.typeParameterIndex[match]!;
	} else {
	translator.typeParameterIndex[parameter] = info.struct.fields.length;
	info.addField(typeType);
	}
	}
	// Add fields for Dart instance fields
	for (Field field in info.cls!.fields) {
	if (field.isInstanceMember) {
	w.ValueType wasmType = translator.translateType(field.type);
	// TODO(askesc): Generalize this check for finer nullability control
	if (wasmType != w.RefType.data()) {
	wasmType = wasmType.withNullability(true);
	}
	translator.fieldIndex[field] = info.struct.fields.length;
	info.addField(w.FieldType(wasmType));
	}
	}
	} else {
	for (TypeParameter parameter in info.cls!.typeParameters) {
	// Reuse supertype type variable
	translator.typeParameterIndex[parameter] =
	translator.typeParameterIndex[info.typeParameterMatch[parameter]]!;
	}
	}
	}

	void collect() {
	// Create class info and Wasm structs for all classes.
	initializeTop();
	// Subclasses of the [_Function] class are generated on the fly as fields
	// with function types are encountered. Therefore, this class must be early
	// in the initialization order.
	initialize(translator.functionClass);
	for (Library library in translator.component.libraries) {
	for (Class cls in library.classes) {
	initialize(cls);
	}
	}

	// For each class, compute which Wasm struct should be used for the type of
	// variables bearing that class as their Dart type. This is the struct
	// corresponding to the least common supertype of all Dart classes
	// implementing this class.
	for (ClassInfo info in translator.classes) {
	computeRepresentation(info);
	}

	// Now that the representation types for all classes have been computed,
	// fill in the types of the fields in the generated Wasm structs.
	for (ClassInfo info in translator.classes) {
	generateFields(info);
	}

	// Add hidden fields of typed_data classes.
	addTypedDataFields();

	// Validate that all internally used fields have the expected indices.
	FieldIndex.validate(translator);
	}

	void addTypedDataFields() {
	ClassInfo typedListBaseInfo =
	translator.classInfo[translator.typedListBaseClass]!;
	typedListBaseInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
	FieldIndex.typedListBaseLength);

	ClassInfo typedListInfo = translator.classInfo[translator.typedListClass]!;
	typedListInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
	FieldIndex.typedListBaseLength);
	w.RefType bytesArrayType = w.RefType.def(
	translator.wasmArrayType(w.PackedType.i8, "i8"),
	nullable: false);
	typedListInfo.addField(
	w.FieldType(bytesArrayType, mutable: false), FieldIndex.typedListArray);

	w.RefType typedListType =
	w.RefType.def(typedListInfo.struct, nullable: false);

	ClassInfo typedListViewInfo =
	translator.classInfo[translator.typedListViewClass]!;
	typedListViewInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
	FieldIndex.typedListBaseLength);
	typedListViewInfo.addField(w.FieldType(typedListType, mutable: false),
	FieldIndex.typedListViewTypedData);
	typedListViewInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
	FieldIndex.typedListViewOffsetInBytes);

	ClassInfo byteDataViewInfo =
	translator.classInfo[translator.byteDataViewClass]!;
	byteDataViewInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
	FieldIndex.byteDataViewLength);
	byteDataViewInfo.addField(w.FieldType(typedListType, mutable: false),
	FieldIndex.byteDataViewTypedData);
	byteDataViewInfo.addField(w.FieldType(w.NumType.i32, mutable: false),
	FieldIndex.byteDataViewOffsetInBytes);
	}
	}