Support serialization of the compiler backbone.

tests/compiler/dart2js/serialization_test.dart

Index: tests/compiler/dart2js/serialization_test.dart
diff --git a/tests/compiler/dart2js/serialization_test.dart b/tests/compiler/dart2js/serialization_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a258c2d6b03332446e2e45931ddc3f6413077a08
--- /dev/null
+++ b/tests/compiler/dart2js/serialization_test.dart
@@ -0,0 +1,1049 @@
+// Copyright (c) 2015, 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.
+
+library dart2js.serialization_test;
+
+import 'dart:io';
+import 'memory_compiler.dart';
+import 'package:async_helper/async_helper.dart';
+import 'package:compiler/src/constants/expressions.dart';
+import 'package:compiler/src/dart_types.dart';
+import 'package:compiler/src/dart2jslib.dart';
+import 'package:compiler/src/elements/elements.dart';
+import 'package:compiler/src/elements/visitor.dart';
+import 'package:compiler/src/ordered_typeset.dart';
+import 'package:compiler/src/serialization/serialization.dart';
+import 'package:compiler/src/serialization/json_serializer.dart';
+import 'package:compiler/src/tree/tree.dart';
+
+main(List<String> arguments) {
+  // Ensure that we can print out constant expressions.
+  DEBUG_MODE = true;
+
+  Uri entryPoint;
+  String outPath;
+  bool prettyPrint = false;
+  for (String arg in arguments) {
+    if (arg.startsWith('--')) {
+      if (arg.startsWith('--out=')) {
+        outPath = arg.substring('--out='.length);
+      } else if (arg == '--pretty-print') {
+        prettyPrint = true;
+      } else {
+        print("Unknown option $arg");
+      }
+    } else {
+      if (entryPoint != null) {
+        print("Multiple entrypoints is not supported.");
+      }
+      entryPoint = Uri.parse(arg);
+    }
+  }
+  if (entryPoint == null) {
+    entryPoint = Uri.parse('dart:core');
+  }
+  Compiler compiler = compilerFor({}, options: ['--analyze-all']);
+  asyncTest(() async {
+    await compiler.runCompiler(entryPoint);
+    testSerialization(compiler.libraryLoader.libraries,
+                      outPath: outPath,
+                      prettyPrint: prettyPrint);
+  });
+}
+
+void testSerialization(Iterable<LibraryElement> libraries1,
+                       {String outPath,
+                        bool prettyPrint}) {
+  Serializer serializer = new Serializer(const JsonSerializationEncoder());
+  for (LibraryElement library1 in libraries1) {
+    serializer.serialize(library1);
+  }
+  String text = serializer.toText();
+  String outText = text;
+  if (prettyPrint) {
+    outText = serializer.prettyPrint();
+  }
+  if (outPath != null) {
+    new File(outPath).writeAsStringSync(outText);
+  } else if (prettyPrint) {
+    print(outText);
+  }
+
+  Deserializer deserializer = new Deserializer.fromText(
+      text, const JsonSerializationDecoder());
+  List<LibraryElement> libraries2 = <LibraryElement>[];
+  for (LibraryElement library1 in libraries1) {
+    LibraryElement library2 =
+        deserializer.lookupLibrary(library1.canonicalUri);
+    if (library2 == null) {
+      throw new ArgumentError('No library ${library1.canonicalUri} found.');
+    }
+    checkLibraryContent('library1', 'library2', 'library', library1, library2);
+    libraries2.add(library2);
+  }
+
+  Serializer serializer2 = new Serializer(const JsonSerializationEncoder());
+  for (LibraryElement library2 in libraries2) {
+    serializer2.serialize(library2);
+  }
+  String text2 = serializer2.toText();
+
+  Deserializer deserializer3 = new Deserializer.fromText(
+      text2, const JsonSerializationDecoder());
+  for (LibraryElement library1 in libraries1) {
+    LibraryElement library2 =
+        deserializer.lookupLibrary(library1.canonicalUri);
+    if (library2 == null) {
+      throw new ArgumentError('No library ${library1.canonicalUri} found.');
+    }
+    LibraryElement library3 =
+        deserializer3.lookupLibrary(library1.canonicalUri);
+    if (library3 == null) {
+      throw new ArgumentError('No library ${library1.canonicalUri} found.');
+    }
+    checkLibraryContent('library1', 'library3', 'library', library1, library3);
+    checkLibraryContent('library2', 'library3', 'library', library2, library3);
+  }
+}
+
+/// Check the equivalence of [library1] and [library2] and their content.
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+checkLibraryContent(
+    Object object1, object2, String property,
+    LibraryElement library1, LibraryElement library2) {
+  checkElementProperties(object1, object2, property, library1, library2);
+}
+
+/// Check the equivalence of [element1] and [element2] and their properties.
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+checkElementProperties(
+    Object object1, object2, String property,
+    Element element1, Element element2) {
+  const ElementPropertyEquivalence().visit(element1, element2);
+}
+
+/// Check the equivalence of the two lists of elements, [list1] and [list2].
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+checkElementLists(Object object1, Object object2, String property,
+                  Iterable<Element> list1, Iterable<Element> list2) {
+  checkListEquivalence(object1, object2, property,
+                  list1, list2, checkElementProperties);
+}
+
+/// Check equivalence of the two lists, [list1] and [list2], using
+/// [checkEquivalence] to check the pair-wise equivalence.
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+void checkListEquivalence(
+    Object object1, Object object2, String property,
+    Iterable list1, Iterable list2,
+    void checkEquivalence(o1, o2, property, a, b)) {
+  for (int i = 0; i < list1.length && i < list2.length; i++) {
+    checkEquivalence(
+        object1, object2, property,
+        list1.elementAt(i), list2.elementAt(i));
+  }
+  for (int i = list1.length; i < list2.length; i++) {
+    throw
+        'Missing equivalent for element '
+        '#$i ${list2.elementAt(i)} in `${property}` on $object2.\n'
+        '`${property}` on $object1:\n ${list1.join('\n ')}\n'
+        '`${property}` on $object2:\n ${list2.join('\n ')}';
+  }
+  for (int i = list2.length; i < list1.length; i++) {
+    throw
+        'Missing equivalent for element '
+        '#$i ${list1.elementAt(i)} in `${property}` on $object1.\n'
+        '`${property}` on $object1:\n ${list1.join('\n ')}\n'
+        '`${property}` on $object2:\n ${list2.join('\n ')}';
+  }
+}
+
+/// Checks the equivalence of the identity (but not properties) of [element1]
+/// and [element2].
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+void checkElementIdentities(
+    Object object1, Object object2, String property,
+    Element element1, Element element2) {
+  if (identical(element1, element2)) return;
+  if (element1 == null || element2 == null) {
+    check(object1, object2, property, element1, element2);
+  }
+  const ElementIdentityEquivalence().visit(element1, element2);
+}
+
+/// Checks the pair-wise equivalence of the identity (but not properties) of the
+/// elements in [list] and [list2].
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+void checkElementListIdentities(
+    Object object1, Object object2, String property,
+    Iterable<Element> list1, Iterable<Element> list2) {
+  checkListEquivalence(
+      object1, object2, property,
+      list1, list2, checkElementIdentities);
+}
+
+/// Checks the equivalence of [type1] and [type2].
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+void checkTypes(
+    Object object1, Object object2, String property,
+    DartType type1, DartType type2) {
+  if (identical(type1, type2)) return;
+  if (type1 == null || type2 == null) {
+    check(object1, object2, property, type1, type2);
+  }
+  const TypeEquivalence().visit(type1, type2);
+}
+
+/// Checks the pair-wise equivalence of the types in [list1] and [list2].
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+void checkTypeLists(
+    Object object1, Object object2, String property,
+    List<DartType> list1, List<DartType> list2) {
+  checkListEquivalence(object1, object2, property, list1, list2, checkTypes);
+}
+
+/// Checks the equivalence of [exp1] and [exp2].
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+void checkConstants(
+    Object object1, Object object2, String property,
+    ConstantExpression exp1, ConstantExpression exp2) {
+  if (identical(exp1, exp2)) return;
+  if (exp1 == null || exp2 == null) {
+    check(object1, object2, property, exp1, exp2);
+  }
+  const ConstantEquivalence().visit(exp1, exp2);
+}
+
+/// Checks the pair-wise equivalence of the contants in [list1] and [list2].
+///
+/// Uses [object1], [object2] and [property] to provide context for failures.
+void checkConstantLists(
+    Object object1, Object object2, String property,
+    List<ConstantExpression> list1,
+    List<ConstantExpression> list2) {
+  checkListEquivalence(
+      object1, object2, property,
+      list1, list2, checkConstants);
+}
+
+/// Checks the equivalence of [constructor1] and [constructor2].
+void constantConstructorEquivalence(ConstantConstructor constructor1,
+                                    ConstantConstructor constructor2) {
+  const ConstantConstructorEquivalence().visit(constructor1, constructor2);
+}
+
+/// Visitor that checks the equivalence of [ConstantConstructor]s.
+class ConstantConstructorEquivalence
+    extends ConstantConstructorVisitor<dynamic, ConstantConstructor> {
+  const ConstantConstructorEquivalence();
+
+  @override
+  void visit(ConstantConstructor constructor1,
+             ConstantConstructor constructor2) {
+    if (identical(constructor1, constructor2)) return;
+    check(constructor1, constructor2, 'kind',
+          constructor1.kind, constructor2.kind);
+    constructor1.accept(this, constructor2);
+  }
+
+  @override
+  visitGenerative(
+      GenerativeConstantConstructor constructor1,
+      GenerativeConstantConstructor constructor2) {
+    checkTypes(
+        constructor1, constructor2, 'type',
+        constructor1.type, constructor2.type);
+    check(constructor1, constructor2, 'defaultValues.length',
+          constructor1.defaultValues.length,
+          constructor2.defaultValues.length);
+    constructor1.defaultValues.forEach((k, v) {
+      checkConstants(
+          constructor1, constructor2, 'defaultValue[$k]',
+          v, constructor2.defaultValues[k]);
+    });
+    check(constructor1, constructor2, 'fieldMap.length',
+          constructor1.fieldMap.length,
+          constructor2.fieldMap.length);
+    constructor1.fieldMap.forEach((k1, v1) {
+      bool matched = false;
+      constructor2.fieldMap.forEach((k2, v2) {
+        if (k1.name == k2.name &&
+            k1.library.canonicalUri == k2.library.canonicalUri) {
+          checkElementIdentities(
+              constructor1, constructor2, 'fieldMap[${k1.name}].key', k1, k2);
+          checkConstants(
+              constructor1, constructor2, 'fieldMap[${k1.name}].value', v1, v2);
+          matched = true;
+        }
+      });
+      if (!matched) {
+        throw 'Unmatched field $k1 = $v1';
+      }
+    });
+    checkConstants(
+        constructor1, constructor2, 'superConstructorInvocation',
+        constructor1.superConstructorInvocation,
+        constructor2.superConstructorInvocation);
+  }
+
+  @override
+  visitRedirectingFactory(
+      RedirectingFactoryConstantConstructor constructor1,
+      RedirectingFactoryConstantConstructor constructor2) {
+    checkConstants(
+        constructor1, constructor2, 'targetConstructorInvocation',
+        constructor1.targetConstructorInvocation,
+        constructor2.targetConstructorInvocation);
+  }
+
+  @override
+  visitRedirectingGenerative(
+      RedirectingGenerativeConstantConstructor constructor1,
+      RedirectingGenerativeConstantConstructor constructor2) {
+    check(constructor1, constructor2, 'defaultValues.length',
+          constructor1.defaultValues.length,
+          constructor2.defaultValues.length);
+    constructor1.defaultValues.forEach((k, v) {
+      checkConstants(
+          constructor1, constructor2, 'defaultValue[$k]',
+          v, constructor2.defaultValues[k]);
+    });
+    checkConstants(
+        constructor1, constructor2, 'thisConstructorInvocation',
+        constructor1.thisConstructorInvocation,
+        constructor2.thisConstructorInvocation);
+  }
+}
+
+/// Check that the values [property] of [object1] and [object2], [value1] and
+/// [value2] respectively, are equal and throw otherwise.
+void check(var object1, var object2, String property, var value1, value2) {
+  if (value1 != value2) {
+    throw "$object1.$property = '${value1}' <> "
+          "$object2.$property = '${value2}'";
+  }
+}
+
+/// Visitor that checks for equivalence of [Element] identities.
+class ElementIdentityEquivalence extends BaseElementVisitor<dynamic, Element> {
+  const ElementIdentityEquivalence();
+
+  void visit(Element element1, Element element2) {
+    check(element1, element2, 'kind', element1.kind, element2.kind);
+    element1.accept(this, element2);
+  }
+
+  @override
+  void visitElement(Element e, Element arg) {
+    throw new UnsupportedError("Unsupported element $e");
+  }
+
+  @override
+  void visitLibraryElement(LibraryElement element1, LibraryElement element2) {
+    check(element1, element2,
+          'canonicalUri',
+          element1.canonicalUri, element2.canonicalUri);
+  }
+
+  @override
+  void visitCompilationUnitElement(CompilationUnitElement element1,
+                                   CompilationUnitElement element2) {
+    check(element1, element2,
+          'name',
+          element1.name, element2.name);
+    visit(element1.library, element2.library);
+  }
+
+  @override
+  void visitClassElement(ClassElement element1, ClassElement element2) {
+    check(element1, element2,
+          'name',
+          element1.name, element2.name);
+    visit(element1.library, element2.library);
+  }
+
+  void checkMembers(Element element1, Element element2) {
+    check(element1, element2,
+          'name',
+          element1.name, element2.name);
+    if (element1.enclosingClass != null || element2.enclosingClass != null) {
+      visit(element1.enclosingClass, element2.enclosingClass);
+    } else {
+      visit(element1.library, element2.library);
+    }
+  }
+
+  @override
+  void visitFieldElement(FieldElement element1, FieldElement element2) {
+    checkMembers(element1, element2);
+  }
+
+  @override
+  void visitFunctionElement(FunctionElement element1,
+                            FunctionElement element2) {
+    checkMembers(element1, element2);
+  }
+
+  void visitAbstractFieldElement(AbstractFieldElement element1,
+                                 AbstractFieldElement element2) {
+    checkMembers(element1, element2);
+  }
+
+  @override
+  void visitTypeVariableElement(TypeVariableElement element1,
+                                TypeVariableElement element2) {
+    check(element1, element2,
+          'name',
+          element1.name, element2.name);
+    visit(element1.typeDeclaration, element2.typeDeclaration);
+  }
+
+  @override
+  void visitTypedefElement(TypedefElement element1, TypedefElement element2) {
+    check(element1, element2,
+          'name',
+          element1.name, element2.name);
+    visit(element1.library, element2.library);
+  }
+
+  @override
+  void visitParameterElement(ParameterElement element1,
+                             ParameterElement element2) {
+    check(element1, element2,
+          'name',
+          element1.name, element2.name);
+    visit(element1.functionDeclaration, element2.functionDeclaration);
+  }
+}
+
+/// Visitor that checks for equivalence of [Element] properties.
+class ElementPropertyEquivalence extends BaseElementVisitor<dynamic, Element> {
+  const ElementPropertyEquivalence();
+
+  void visit(Element element1, Element element2) {
+    if (element1 == element2) return;
+    check(element1, element2, 'kind', element1.kind, element2.kind);
+    element1.accept(this, element2);
+  }
+
+  @override
+  void visitElement(Element e, Element arg) {
+    throw new UnsupportedError("Unsupported element $e");
+  }
+
+  @override
+  void visitLibraryElement(LibraryElement element1, LibraryElement element2) {
+    checkElementIdentities(null, null, null, element1, element2);
+    check(element1, element2, 'name', element1.name, element2.name);
+    check(element1, element2, 'getLibraryName',
+          element1.getLibraryName(), element2.getLibraryName());
+    visitMembers(element1, element2);
+    visit(element1.entryCompilationUnit, element2.entryCompilationUnit);
+    checkElementLists(
+        element1, element2, 'compilationUnits',
+        element1.compilationUnits.toList(),
+        element2.compilationUnits.toList());
+
+    bool filterTags(LibraryTag tag) => tag.asLibraryDependency() != null;
+
+    List<LibraryTag> tags1 = element1.tags.where(filterTags).toList();
+    List<LibraryTag> tags2 = element2.tags.where(filterTags).toList();
+    checkListEquivalence(element1, element2, 'tags', tags1, tags2,
+        (Object object1, Object object2, String property,
+         LibraryDependency tag1, LibraryDependency tag2) {
+      checkElementIdentities(
+          tag1, tag2, 'getLibraryFromTag',
+          element1.getLibraryFromTag(tag1),
+          element2.getLibraryFromTag(tag2));
+    });
+
+    List<Element> imports1 = <Element>[];
+    List<Element> imports2 = <Element>[];
+    element1.forEachImport((Element import) {
+      if (import.isAmbiguous) return;
+      imports1.add(import);
+    });
+    element2.forEachImport((Element import) {
+      if (import.isAmbiguous) return;
+      imports2.add(import);
+    });
+    checkElementListIdentities(
+        element1, element2, 'imports', imports1, imports2);
+
+    List<Element> exports1 = <Element>[];
+    List<Element> exports2 = <Element>[];
+    element1.forEachExport((Element export) {
+      if (export.isAmbiguous) return;
+      exports1.add(export);
+    });
+    element2.forEachExport((Element export) {
+      if (export.isAmbiguous) return;
+      exports2.add(export);
+    });
+    checkElementListIdentities(
+        element1, element2, 'exports', exports1, exports2);
+  }
+
+  @override
+  void visitCompilationUnitElement(CompilationUnitElement element1,
+                                   CompilationUnitElement element2) {
+    check(element1, element2,
+          'name',
+          element1.name, element2.name);
+    checkElementIdentities(
+        element1, element2, 'library',
+        element1.library, element2.library);
+    check(element1, element2,
+          'script.resourceUri',
+          element1.script.resourceUri, element2.script.resourceUri);
+    List<Element> members1 = <Element>[];
+    List<Element> members2 = <Element>[];
+    element1.forEachLocalMember((Element member) {
+      members1.add(member);
+    });
+    element2.forEachLocalMember((Element member) {
+      members2.add(member);
+    });
+    checkElementListIdentities(
+        element1, element2, 'localMembers', members1, members2);
+  }
+
+  void visitMembers(ScopeContainerElement element1,
+                    ScopeContainerElement element2) {
+    Set<String> names = new Set<String>();
+    element1.forEachLocalMember((Element member) {
+      names.add(member.name);
+    });
+    element2.forEachLocalMember((Element member) {
+      names.add(member.name);
+    });
+    for (String name in names) {
+      Element member1 = element1.localLookup(name);
+      Element member2 = element2.localLookup(name);
+      if (member1 == null) {
+        print('Missing member for $member2');
+        continue;
+      }
+      if (member2 == null) {
+        print('Missing member for $member1');
+        continue;
+      }
+      visit(member1, member2);
+    }
+  }
+
+  @override
+  void visitClassElement(ClassElement element1, ClassElement element2) {
+    checkElementIdentities(null, null, null, element1, element2);
+    check(element1, element2, 'name',
+          element1.name, element2.name);
+    check(element1, element2, 'sourcePosition',
+          element1.sourcePosition, element2.sourcePosition);
+    checkElementIdentities(
+        element1, element2, 'library',
+        element1.library, element2.library);
+    checkElementIdentities(
+        element1, element2, 'compilationUnit',
+        element1.compilationUnit, element2.compilationUnit);
+    check(element1, element2, 'isObject',
+        element1.isObject, element2.isObject);
+    checkTypeLists(element1, element2, 'typeVariables',
+        element1.typeVariables, element2.typeVariables);
+    check(element1, element2, 'isAbstract',
+        element1.isAbstract, element2.isAbstract);
+    if (!element1.isObject) {
+      checkTypes(element1, element2, 'supertype',
+          element1.supertype, element2.supertype);
+    }
+    check(element1, element2, 'hierarchyDepth',
+          element1.hierarchyDepth, element2.hierarchyDepth);
+    checkTypeLists(
+        element1, element2, 'allSupertypes',
+        element1.allSupertypes.toList(),
+        element2.allSupertypes.toList());
+    OrderedTypeSet typeSet1 = element1.allSupertypesAndSelf;
+    OrderedTypeSet typeSet2 = element1.allSupertypesAndSelf;
+    checkListEquivalence(
+        element1, element2, 'allSupertypes',
+        typeSet1.levelOffsets,
+        typeSet2.levelOffsets,
+        check);
+    check(element1, element2, 'allSupertypesAndSelf.levels',
+          typeSet1.levels, typeSet2.levels);
+    checkTypeLists(
+        element1, element2, 'supertypes',
+        typeSet1.supertypes.toList(),
+        typeSet2.supertypes.toList());
+    checkTypeLists(
+        element1, element2, 'types',
+        typeSet1.types.toList(),
+        typeSet2.types.toList());
+
+    checkTypeLists(
+        element1, element2, 'interfaces',
+        element1.interfaces.toList(),
+        element2.interfaces.toList());
+
+    visitMembers(element1, element2);
+  }
+
+  @override
+  void visitFieldElement(FieldElement element1, FieldElement element2) {
+    checkElementIdentities(null, null, null, element1, element2);
+    check(element1, element2, 'name',
+          element1.name, element2.name);
+    check(element1, element2, 'sourcePosition',
+          element1.sourcePosition, element2.sourcePosition);
+    checkTypes(
+        element1, element2, 'type',
+        element1.type, element2.type);
+    check(element1, element2, 'isConst',
+          element1.isConst, element2.isConst);
+    check(element1, element2, 'isFinal',
+          element1.isFinal, element2.isFinal);
+    if (element1.isConst) {
+      checkConstants(
+          element1, element2, 'constant',
+          element1.constant, element2.constant);
+    }
+    check(element1, element2, 'isTopLevel',
+          element1.isTopLevel, element2.isTopLevel);
+    check(element1, element2, 'isStatic',
+          element1.isStatic, element2.isStatic);
+    check(element1, element2, 'isInstanceMember',
+          element1.isInstanceMember, element2.isInstanceMember);
+
+    checkElementIdentities(
+        element1, element2, 'library',
+        element1.library, element2.library);
+    checkElementIdentities(
+        element1, element2, 'compilationUnit',
+        element1.compilationUnit, element2.compilationUnit);
+    checkElementIdentities(
+        element1, element2, 'enclosingClass',
+        element1.enclosingClass, element2.enclosingClass);
+  }
+
+  @override
+  void visitFunctionElement(FunctionElement element1,
+                            FunctionElement element2) {
+    checkElementIdentities(null, null, null, element1, element2);
+    check(element1, element2, 'name',
+          element1.name, element2.name);
+    check(element1, element2, 'sourcePosition',
+          element1.sourcePosition, element2.sourcePosition);
+    checkTypes(
+        element1, element2, 'type',
+        element1.type, element2.type);
+    checkListEquivalence(
+        element1, element2, 'parameters',
+        element1.parameters, element2.parameters,
+        checkElementProperties);
+    check(element1, element2, 'isOperator',
+          element1.isOperator, element2.isOperator);
+
+    checkElementIdentities(
+        element1, element2, 'library',
+        element1.library, element2.library);
+    checkElementIdentities(
+        element1, element2, 'compilationUnit',
+        element1.compilationUnit, element2.compilationUnit);
+    checkElementIdentities(
+        element1, element2, 'enclosingClass',
+        element1.enclosingClass, element2.enclosingClass);
+  }
+
+  @override
+  void visitConstructorElement(ConstructorElement element1,
+                               ConstructorElement element2) {
+    checkElementIdentities(null, null, null, element1, element2);
+    checkElementIdentities(
+        element1, element2, 'enclosingClass',
+        element1.enclosingClass, element2.enclosingClass);
+    check(
+        element1, element2, 'name',
+        element1.name, element2.name);
+    check(element1, element2, 'sourcePosition',
+          element1.sourcePosition, element2.sourcePosition);
+    checkListEquivalence(
+        element1, element2, 'parameters',
+        element1.parameters, element2.parameters,
+        checkElementProperties);
+    checkTypes(
+        element1, element2, 'type',
+        element1.type, element2.type);
+    check(element1, element2, 'isConst',
+          element1.isConst, element2.isConst);
+    check(element1, element2, 'isExternal',
+          element1.isExternal, element2.isExternal);
+    if (element1.isConst && !element1.isExternal) {
+      constantConstructorEquivalence(
+          element1.constantConstructor,
+          element2.constantConstructor);
+    }
+  }
+
+  @override
+  void visitAbstractFieldElement(AbstractFieldElement element1,
+                                 AbstractFieldElement element2) {
+    visit(element1.getter, element2.getter);
+    visit(element1.setter, element2.setter);
+  }
+
+  @override
+  void visitTypeVariableElement(TypeVariableElement element1,
+                                TypeVariableElement element2) {
+    checkElementIdentities(null, null, null, element1, element2);
+    check(element1, element2, 'name', element1.name, element2.name);
+    check(element1, element2, 'sourcePosition',
+          element1.sourcePosition, element2.sourcePosition);
+    check(element1, element2, 'index', element1.index, element2.index);
+    checkTypes(
+        element1, element2, 'type',
+        element1.type, element2.type);
+    checkTypes(
+        element1, element2, 'bound',
+        element1.bound, element2.bound);
+  }
+
+  @override
+  void visitTypedefElement(TypedefElement element1,
+                           TypedefElement element2) {
+    checkElementIdentities(null, null, null, element1, element2);
+    check(element1, element2, 'name', element1.name, element2.name);
+    check(element1, element2, 'sourcePosition',
+          element1.sourcePosition, element2.sourcePosition);
+    checkTypes(
+        element1, element2, 'alias',
+        element1.alias, element2.alias);
+    checkTypeLists(
+        element1, element2, 'typeVariables',
+        element1.typeVariables, element2.typeVariables);
+    checkElementIdentities(
+        element1, element2, 'library',
+        element1.library, element2.library);
+    checkElementIdentities(
+        element1, element2, 'compilationUnit',
+        element1.compilationUnit, element2.compilationUnit);
+    // TODO(johnniwinther): Check the equivalence of typedef parameters.
+  }
+
+  @override
+  void visitParameterElement(ParameterElement element1,
+                             ParameterElement element2) {
+    checkElementIdentities(null, null, null, element1, element2);
+    checkElementIdentities(
+        element1, element2, 'functionDeclaration',
+        element1.functionDeclaration, element2.functionDeclaration);
+    check(element1, element2, 'name', element1.name, element2.name);
+    check(element1, element2, 'sourcePosition',
+          element1.sourcePosition, element2.sourcePosition);
+    checkTypes(
+        element1, element2, 'type',
+        element1.type, element2.type);
+    check(
+        element1, element2, 'isOptional',
+        element1.isOptional, element2.isOptional);
+    check(
+        element1, element2, 'isNamed',
+        element1.isNamed, element2.isNamed);
+    check(element1, element2, 'name', element1.name, element2.name);
+    if (element1.isOptional) {
+      checkConstants(
+          element1, element2, 'constant',
+          element1.constant, element2.constant);
+    }
+    checkElementIdentities(
+        element1, element2, 'compilationUnit',
+        element1.compilationUnit, element2.compilationUnit);
+  }
+
+  @override
+  void visitFieldParameterElement(InitializingFormalElement element1,
+                                  InitializingFormalElement element2) {
+    visitParameterElement(element1, element2);
+    checkElementIdentities(
+        element1, element2, 'fieldElement',
+        element1.fieldElement, element2.fieldElement);
+  }
+}
+
+/// Visitor that checks for equivalence of [DartType]s.
+class TypeEquivalence implements DartTypeVisitor<dynamic, DartType> {
+  const TypeEquivalence();
+
+  void visit(DartType type1, DartType type2) {
+    check(type1, type2, 'kind', type1.kind, type2.kind);
+    type1.accept(this, type2);
+  }
+
+  @override
+  void visitDynamicType(DynamicType type, DynamicType other) {
+  }
+
+  @override
+  void visitFunctionType(FunctionType type, FunctionType other) {
+    checkTypeLists(
+        type, other, 'parameterTypes',
+        type.parameterTypes, other.parameterTypes);
+    checkTypeLists(
+        type, other, 'optionalParameterTypes',
+        type.optionalParameterTypes, other.optionalParameterTypes);
+    checkTypeLists(
+        type, other, 'namedParameterTypes',
+        type.namedParameterTypes, other.namedParameterTypes);
+    for (int i = 0; i < type.namedParameters.length; i++) {
+      if (type.namedParameters[i] != other.namedParameters[i]) {
+        throw "Named parameter '$type.namedParameters[i]' <> "
+              "'${other.namedParameters[i]}'";
+      }
+    }
+  }
+
+  void visitGenericType(GenericType type, GenericType other) {
+    checkElementIdentities(
+        type, other, 'element',
+        type.element, other.element);
+    checkTypeLists(
+        type, other, 'typeArguments',
+        type.typeArguments, other.typeArguments);
+  }
+
+  @override
+  void visitMalformedType(MalformedType type, MalformedType other) {
+  }
+
+  @override
+  void  visitStatementType(StatementType type, StatementType other) {
+    throw new UnsupportedError("Unsupported type: $type");
+  }
+
+  @override
+  void visitTypeVariableType(TypeVariableType type, TypeVariableType other) {
+    checkElementIdentities(
+        type, other, 'element',
+        type.element, other.element);
+  }
+
+  @override
+  void visitVoidType(VoidType type, VoidType argument) {
+  }
+
+  @override
+  void visitInterfaceType(InterfaceType type, InterfaceType other) {
+    visitGenericType(type, other);
+  }
+
+  @override
+  void visitTypedefType(TypedefType type, TypedefType other) {
+    visitGenericType(type, other);
+  }
+}
+
+/// Visitor that checks for structural equivalence of [ConstantExpression]s.
+class ConstantEquivalence
+    implements ConstantExpressionVisitor<dynamic, ConstantExpression> {
+  const ConstantEquivalence();
+
+  @override
+  visit(ConstantExpression exp1, ConstantExpression exp2) {
+    if (identical(exp1, exp2)) return;
+    check(exp1, exp2, 'kind', exp1.kind, exp2.kind);
+    exp1.accept(this, exp2);
+  }
+
+  @override
+  visitBinary(BinaryConstantExpression exp1, BinaryConstantExpression exp2) {
+    check(exp1, exp2, 'operator', exp1.operator, exp2.operator);
+    checkConstants(exp1, exp2, 'left', exp1.left, exp2.left);
+    checkConstants(exp1, exp2, 'right', exp1.right, exp2.right);
+  }
+
+  @override
+  visitConcatenate(ConcatenateConstantExpression exp1,
+                   ConcatenateConstantExpression exp2) {
+    checkConstantLists(
+        exp1, exp2, 'expressions',
+        exp1.expressions, exp2.expressions);
+  }
+
+  @override
+  visitConditional(ConditionalConstantExpression exp1,
+                   ConditionalConstantExpression exp2) {
+    checkConstants(
+        exp1, exp2, 'condition', exp1.condition, exp2.condition);
+    checkConstants(exp1, exp2, 'trueExp', exp1.trueExp, exp2.trueExp);
+    checkConstants(exp1, exp2, 'falseExp', exp1.falseExp, exp2.falseExp);
+  }
+
+  @override
+  visitConstructed(ConstructedConstantExpression exp1,
+                   ConstructedConstantExpression exp2) {
+    checkTypes(
+        exp1, exp2, 'type',
+        exp1.type, exp2.type);
+    checkElementIdentities(
+        exp1, exp2, 'target',
+        exp1.target, exp2.target);
+    checkConstantLists(
+        exp1, exp2, 'arguments',
+        exp1.arguments, exp2.arguments);
+    check(exp1, exp2, 'callStructure', exp1.callStructure, exp2.callStructure);
+  }
+
+  @override
+  visitFunction(FunctionConstantExpression exp1,
+                FunctionConstantExpression exp2) {
+    checkElementIdentities(
+        exp1, exp2, 'element',
+        exp1.element, exp2.element);
+  }
+
+  @override
+  visitIdentical(IdenticalConstantExpression exp1,
+                 IdenticalConstantExpression exp2) {
+    checkConstants(exp1, exp2, 'left', exp1.left, exp2.left);
+    checkConstants(exp1, exp2, 'right', exp1.right, exp2.right);
+  }
+
+  @override
+  visitList(ListConstantExpression exp1, ListConstantExpression exp2) {
+    checkTypes(
+        exp1, exp2, 'type',
+        exp1.type, exp2.type);
+    checkConstantLists(
+        exp1, exp2, 'values',
+        exp1.values, exp2.values);
+  }
+
+  @override
+  visitMap(MapConstantExpression exp1, MapConstantExpression exp2) {
+    checkTypes(
+        exp1, exp2, 'type',
+        exp1.type, exp2.type);
+    checkConstantLists(
+        exp1, exp2, 'keys',
+        exp1.keys, exp2.keys);
+    checkConstantLists(
+        exp1, exp2, 'values',
+        exp1.values, exp2.values);
+  }
+
+  @override
+  visitNamed(NamedArgumentReference exp1, NamedArgumentReference exp2) {
+    check(exp1, exp2, 'name', exp1.name, exp2.name);
+  }
+
+  @override
+  visitPositional(PositionalArgumentReference exp1,
+                  PositionalArgumentReference exp2) {
+    check(exp1, exp2, 'index', exp1.index, exp2.index);
+  }
+
+  @override
+  visitSymbol(SymbolConstantExpression exp1, SymbolConstantExpression exp2) {
+    // TODO: implement visitSymbol
+  }
+
+  @override
+  visitType(TypeConstantExpression exp1, TypeConstantExpression exp2) {
+    checkTypes(
+        exp1, exp2, 'type',
+        exp1.type, exp2.type);
+  }
+
+  @override
+  visitUnary(UnaryConstantExpression exp1, UnaryConstantExpression exp2) {
+    check(exp1, exp2, 'operator', exp1.operator, exp2.operator);
+    checkConstants(
+        exp1, exp2, 'expression', exp1.expression, exp2.expression);
+  }
+
+  @override
+  visitVariable(VariableConstantExpression exp1,
+                VariableConstantExpression exp2) {
+    checkElementIdentities(
+        exp1, exp2, 'element',
+        exp1.element, exp2.element);
+  }
+
+  @override
+  visitBool(BoolConstantExpression exp1, BoolConstantExpression exp2) {
+    check(exp1, exp2, 'primitiveValue',
+          exp1.primitiveValue, exp2.primitiveValue);
+  }
+
+  @override
+  visitDouble(DoubleConstantExpression exp1, DoubleConstantExpression exp2) {
+    check(exp1, exp2, 'primitiveValue',
+          exp1.primitiveValue, exp2.primitiveValue);
+  }
+
+  @override
+  visitInt(IntConstantExpression exp1, IntConstantExpression exp2) {
+    check(exp1, exp2, 'primitiveValue',
+          exp1.primitiveValue, exp2.primitiveValue);
+  }
+
+  @override
+  visitNull(NullConstantExpression exp1, NullConstantExpression exp2) {
+    // Do nothing.
+  }
+
+  @override
+  visitString(StringConstantExpression exp1, StringConstantExpression exp2) {
+    check(exp1, exp2, 'primitiveValue',
+          exp1.primitiveValue, exp2.primitiveValue);
+  }
+
+  @override
+  visitBoolFromEnvironment(BoolFromEnvironmentConstantExpression exp1,
+                           BoolFromEnvironmentConstantExpression exp2) {
+    checkConstants(exp1, exp2, 'name', exp1.name, exp2.name);
+    checkConstants(
+        exp1, exp2, 'defaultValue',
+        exp1.defaultValue, exp2.defaultValue);
+  }
+
+  @override
+  visitIntFromEnvironment(IntFromEnvironmentConstantExpression exp1,
+                          IntFromEnvironmentConstantExpression exp2) {
+    checkConstants(exp1, exp2, 'name', exp1.name, exp2.name);
+    checkConstants(
+        exp1, exp2, 'defaultValue',
+        exp1.defaultValue, exp2.defaultValue);
+  }
+
+  @override
+  visitStringFromEnvironment(StringFromEnvironmentConstantExpression exp1,
+                             StringFromEnvironmentConstantExpression exp2) {
+    checkConstants(exp1, exp2, 'name', exp1.name, exp2.name);
+    checkConstants(
+        exp1, exp2, 'defaultValue',
+        exp1.defaultValue, exp2.defaultValue);
+  }
+
+  @override
+  visitStringLength(StringLengthConstantExpression exp1,
+                    StringLengthConstantExpression exp2) {
+    checkConstants(
+        exp1, exp2, 'expression',
+        exp1.expression, exp2.expression);
+  }
+
+  @override
+  visitDeferred(DeferredConstantExpression exp1,
+                DeferredConstantExpression exp2) {
+    // TODO: implement visitDeferred
+  }
+}