dart2js: Use an abstract Name class for names in the generated JavaScript ast.

pkg/compiler/lib/src/js_backend/namer.dart

 // Copyright (c) 2011, 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.
 
 part of js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  *
  * Names are generated through three stages:
@@ skipping 325 matching lines @@
   final String methodsWithOptionalArgumentsField =
       r'$methodsWithOptionalArguments';
   final String deferredAction = r'$deferredAction';
 
   final String classDescriptorProperty = r'^';
   final String requiredParameterField = r'$requiredArgCount';
 
   /// The non-minifying namer's [callPrefix] with a dollar after it.
   static const String _callPrefixDollar = r'call$';
 
+  static final jsAst.Name literalSuper = new StringBackedName("super");
+  static final jsAst.Name literalDollar = new StringBackedName(r'$');
+  static final jsAst.Name literalUnderscore = new StringBackedName('_');
+  static final jsAst.Name literalPlus = new StringBackedName('+');
+  static final jsAst.Name literalDynamic = new StringBackedName("dynamic");
+
   // Name of property in a class description for the native dispatch metadata.
   final String nativeSpecProperty = '%';
 
   static final RegExp IDENTIFIER = new RegExp(r'^[A-Za-z_$][A-Za-z0-9_$]*$');
   static final RegExp NON_IDENTIFIER_CHAR = new RegExp(r'[^A-Za-z_0-9$]');
 
   final Compiler compiler;
 
   /// Used disambiguated names in the global namespace, issued by
   /// [_disambiguateGlobal], and [_disambiguateInternalGlobal].
   ///
   /// Although global names are distributed across a number of global objects,
   /// (see [globalObjectFor]), we currently use a single namespace for all these
   /// names.
   final Set<String> usedGlobalNames = new Set<String>();
-  final Map<Element, String> userGlobals = <Element, String>{};
-  final Map<String, String> internalGlobals = <String, String>{};
+  final Map<Element, jsAst.Name> userGlobals =
+      new HashMap<Element, jsAst.Name>();
+  final Map<String, jsAst.Name> internalGlobals =
+      new HashMap<String, jsAst.Name>();
 
   /// Used disambiguated names in the instance namespace, issued by
   /// [_disambiguateMember], [_disambiguateInternalMember],
   /// [_disambiguateOperator], and [reservePublicMemberName].
   final Set<String> usedInstanceNames = new Set<String>();
-  final Map<String, String> userInstanceMembers = <String, String>{};
-  final Map<Element, String> internalInstanceMembers = <Element, String>{};
-  final Map<String, String> userInstanceOperators = <String, String>{};
+  final Map<String, jsAst.Name> userInstanceMembers =
+      new HashMap<String, jsAst.Name>();
+  final Map<Element, jsAst.Name> internalInstanceMembers =
+      new HashMap<Element, jsAst.Name>();
+  final Map<String, jsAst.Name> userInstanceOperators =
+      new HashMap<String, jsAst.Name>();
 
   final Map<String, int> popularNameCounters = <String, int>{};
 
-  final Map<ConstantValue, String> constantNames = <ConstantValue, String>{};
+  final Map<LibraryElement, String> libraryLongNames =
+      new HashMap<LibraryElement, String>();
+
+  final Map<ConstantValue, jsAst.Name> constantNames =
+      new HashMap<ConstantValue, jsAst.Name>();
   final Map<ConstantValue, String> constantLongNames =
       <ConstantValue, String>{};
   ConstantCanonicalHasher constantHasher;
 
   /// Maps private names to a library that may use that name without prefixing
   /// itself. Used for building proposed names.
   final Map<String, LibraryElement> shortPrivateNameOwners =
       <String, LibraryElement>{};
 
   /// Maps proposed names to *suggested* disambiguated names.
   ///
   /// Suggested names are hints to the [MinifyNamer], suggesting that a specific
   /// names be given to the first item with the given proposed name.
   ///
   /// This is currently used in [MinifyNamer] to assign very short minified
   /// names to things that tend to be used very often.
   final Map<String, String> suggestedGlobalNames = <String, String>{};
   final Map<String, String> suggestedInstanceNames = <String, String>{};
 
+  /// Used to store unique keys for library names. Keys are not used as names,
+  /// nor are they visible in the output. The only serve as an internal
+  /// key into maps.
+  final Map<LibraryElement, String> _libraryKeys =
+      new HashMap<LibraryElement, String>();
+
   Namer(Compiler compiler)
       : compiler = compiler,
         constantHasher = new ConstantCanonicalHasher(compiler),
         functionTypeNamer = new FunctionTypeNamer(compiler);
 
   JavaScriptBackend get backend => compiler.backend;
 
   String get deferredTypesName => 'deferredTypes';
   String get isolateName => 'Isolate';
   String get isolatePropertiesName => r'$isolateProperties';
-  String get noSuchMethodName => publicInstanceMethodNameByArity(
+  jsAst.Name get noSuchMethodName => publicInstanceMethodNameByArity(
       Compiler.NO_SUCH_METHOD, Compiler.NO_SUCH_METHOD_ARG_COUNT);
   /**
    * Some closures must contain their name. The name is stored in
    * [STATIC_CLOSURE_NAME_NAME].
    */
   String get STATIC_CLOSURE_NAME_NAME => r'$name';
   String get closureInvocationSelectorName => Compiler.CALL_OPERATOR_NAME;
   bool get shouldMinify => false;
 
   /// Returns the string that is to be used as the result of a call to
   /// [JS_GET_NAME] at [node] with argument [name].
-  String getNameForJsGetName(Node node, JsGetName name) {
+  jsAst.Name getNameForJsGetName(Node node, JsGetName name) {
     switch (name) {
-      case JsGetName.GETTER_PREFIX: return getterPrefix;
-      case JsGetName.SETTER_PREFIX: return setterPrefix;
-      case JsGetName.CALL_PREFIX: return callPrefix;
-      case JsGetName.CALL_PREFIX0: return '${callPrefix}\$0';
-      case JsGetName.CALL_PREFIX1: return '${callPrefix}\$1';
-      case JsGetName.CALL_PREFIX2: return '${callPrefix}\$2';
-      case JsGetName.CALL_PREFIX3: return '${callPrefix}\$3';
-      case JsGetName.CALL_CATCH_ALL: return callCatchAllName;
-      case JsGetName.REFLECTABLE: return reflectableField;
+      case JsGetName.GETTER_PREFIX: return asName(getterPrefix);
+      case JsGetName.SETTER_PREFIX: return asName(setterPrefix);
+      case JsGetName.CALL_PREFIX: return asName(callPrefix);
+      case JsGetName.CALL_PREFIX0: return asName('${callPrefix}\$0');
+      case JsGetName.CALL_PREFIX1: return asName('${callPrefix}\$1');
+      case JsGetName.CALL_PREFIX2: return asName('${callPrefix}\$2');
+      case JsGetName.CALL_PREFIX3: return asName('${callPrefix}\$3');
+      case JsGetName.CALL_CATCH_ALL: return asName(callCatchAllName);
+      case JsGetName.REFLECTABLE: return asName(reflectableField);
       case JsGetName.CLASS_DESCRIPTOR_PROPERTY:
-        return classDescriptorProperty;
+        return asName(classDescriptorProperty);
       case JsGetName.REQUIRED_PARAMETER_PROPERTY:
-        return requiredParameterField;
-      case JsGetName.DEFAULT_VALUES_PROPERTY: return defaultValuesField;
-      case JsGetName.CALL_NAME_PROPERTY: return callNameField;
-      case JsGetName.DEFERRED_ACTION_PROPERTY: return deferredAction;
-      case JsGetName.OPERATOR_AS_PREFIX: return operatorAsPrefix;
-      case JsGetName.SIGNATURE_NAME: return operatorSignature;
-      case JsGetName.TYPEDEF_TAG: return typedefTag;
+        return asName(requiredParameterField);
+      case JsGetName.DEFAULT_VALUES_PROPERTY: return asName(defaultValuesField);
+      case JsGetName.CALL_NAME_PROPERTY: return asName(callNameField);
+      case JsGetName.DEFERRED_ACTION_PROPERTY: return asName(deferredAction);
+      case JsGetName.OPERATOR_AS_PREFIX: return asName(operatorAsPrefix);
+      case JsGetName.SIGNATURE_NAME: return asName(operatorSignature);
+      case JsGetName.TYPEDEF_TAG: return asName(typedefTag);
       case JsGetName.FUNCTION_TYPE_VOID_RETURN_TAG:
-        return functionTypeVoidReturnTag;
+        return asName(functionTypeVoidReturnTag);
       case JsGetName.FUNCTION_TYPE_RETURN_TYPE_TAG:
-        return functionTypeReturnTypeTag;
+        return asName(functionTypeReturnTypeTag);
       case JsGetName.FUNCTION_TYPE_REQUIRED_PARAMETERS_TAG:
-        return functionTypeRequiredParametersTag;
+        return asName(functionTypeRequiredParametersTag);
       case JsGetName.FUNCTION_TYPE_OPTIONAL_PARAMETERS_TAG:
-        return functionTypeOptionalParametersTag;
+        return asName(functionTypeOptionalParametersTag);
       case JsGetName.FUNCTION_TYPE_NAMED_PARAMETERS_TAG:
-        return functionTypeNamedParametersTag;
+        return asName(functionTypeNamedParametersTag);
       case JsGetName.IS_INDEXABLE_FIELD_NAME:
         Element cls = backend.findHelper('JavaScriptIndexingBehavior');
         return operatorIs(cls);
+      case JsGetName.NULL_CLASS_TYPE_NAME:
+        return runtimeTypeName(compiler.nullClass);
+      case JsGetName.OBJECT_CLASS_TYPE_NAME:
+        return runtimeTypeName(compiler.objectClass);
+      case JsGetName.FUNCTION_CLASS_TYPE_NAME:
+        return runtimeTypeName(compiler.functionClass);
       default:
         compiler.reportError(
           node, MessageKind.GENERIC,
           {'text': 'Error: Namer has no name for "$name".'});
-        return 'BROKEN';
+        return asName('BROKEN');
     }
   }
 
   /// Disambiguated name for [constant].
   ///
   /// Unique within the global-member namespace.
-  String constantName(ConstantValue constant) {
+  jsAst.Name constantName(ConstantValue constant) {
     // In the current implementation it doesn't make sense to give names to
     // function constants since the function-implementation itself serves as
     // constant and can be accessed directly.
     assert(!constant.isFunction);
-    String result = constantNames[constant];
+    jsAst.Name result = constantNames[constant];
     if (result == null) {
       String longName = constantLongName(constant);
       result = getFreshName(longName, usedGlobalNames, suggestedGlobalNames);
       constantNames[constant] = result;
     }
     return result;
   }
 
   /// Proposed name for [constant].
   String constantLongName(ConstantValue constant) {
@@ skipping 46 matching lines @@
     // The first library asking for a short private name wins.
     LibraryElement owner =
         shortPrivateNameOwners.putIfAbsent(text, () => library);
 
     if (owner == library) {
       return text;
     } else {
       // Make sure to return a private name that starts with _ so it
       // cannot clash with any public names.
       // The name is still not guaranteed to be unique, since both the library
-      // name and originalName could contain $ symbols.
-      String libraryName = _disambiguateGlobal(library);
-      return '_$libraryName\$${text}';
+      // name and originalName could contain $ symbols and as the library
+      // name itself might clash.
+      String libraryName = _proposeNameForGlobal(library);
+      return "_$libraryName\$$text";
     }
   }
 
-  String _proposeNameForConstructorBody(ConstructorBodyElement method) {
+  _proposeNameForConstructorBody(ConstructorBodyElement method) {

[floitsch, 2015/06/22 17:43:44]

returns a String.

[herhut, 2015/06/23 13:26:30]

Done.

     String name = Elements.reconstructConstructorNameSourceString(method);
     // We include the method suffix on constructor bodies. It has no purpose,
     // but this way it produces the same names as previous versions of the
     // Namer class did.
     List<String> suffix = callSuffixForSignature(method.functionSignature);
     return '$name\$${suffix.join(r'$')}';
   }
 
   /// Annotated name for [method] encoding arity and named parameters.
-  String instanceMethodName(FunctionElement method) {
+  jsAst.Name instanceMethodName(FunctionElement method) {
     if (method.isGenerativeConstructorBody) {
       return _disambiguateInternalMember(method,
           () => _proposeNameForConstructorBody(method));
     }
     return invocationName(new Selector.fromElement(method));
   }
 
   /// Annotated name for a public method with the given [originalName]
   /// and [arity] and no named parameters.
-  String publicInstanceMethodNameByArity(String originalName, int arity) {
+  jsAst.Name publicInstanceMethodNameByArity(String originalName,
+                                                int arity) {

[floitsch, 2015/06/22 17:43:44]

indentation.

[herhut, 2015/06/23 13:26:30]

Done.

     return invocationName(new Selector.call(originalName, null, arity));
   }
 
   /// Returns the annotated name for a variant of `call`.
   /// The result has the form:
   ///
   ///     call$<N>$namedParam1...$namedParam<M>
   ///
   /// This name cannot be minified because it is generated by string
   /// concatenation at runtime, by applyFunction in js_helper.dart.
-  String deriveCallMethodName(List<String> suffix) {
+  jsAst.Name deriveCallMethodName(List<String> suffix) {
     // TODO(asgerf): Avoid clashes when named parameters contain $ symbols.
-    return '$callPrefix\$${suffix.join(r'$')}';
+    return new StringBackedName('$callPrefix\$${suffix.join(r'$')}');
   }
 
   /// The suffix list for the pattern:
   ///
   ///     $<N>$namedParam1...$namedParam<M>
   ///
   /// This is used for the annotated names of `call`, and for the proposed name
   /// for other instance methods.
   List<String> callSuffixForStructure(CallStructure callStructure) {
     List<String> suffixes = ['${callStructure.argumentCount}'];
@@ skipping 11 matching lines @@
     List<String> suffixes = ['${sig.parameterCount}'];
     if (sig.optionalParametersAreNamed) {
       for (FormalElement param in sig.orderedOptionalParameters) {
         suffixes.add(param.name);
       }
     }
     return suffixes;
   }
 
   /// Annotated name for the member being invoked by [selector].
-  String invocationName(Selector selector) {
+  jsAst.Name invocationName(Selector selector) {
     switch (selector.kind) {
       case SelectorKind.GETTER:
-        String disambiguatedName = _disambiguateMember(selector.memberName);
+        jsAst.Name disambiguatedName =
+            _disambiguateMember(selector.memberName);
         return deriveGetterName(disambiguatedName);
 
       case SelectorKind.SETTER:
-        String disambiguatedName = _disambiguateMember(selector.memberName);
+        jsAst.Name disambiguatedName =
+            _disambiguateMember(selector.memberName);
         return deriveSetterName(disambiguatedName);
 
       case SelectorKind.OPERATOR:
       case SelectorKind.INDEX:
         String operatorIdentifier = operatorNameToIdentifier(selector.name);
-        String disambiguatedName = _disambiguateOperator(operatorIdentifier);
+        jsAst.Name disambiguatedName =
+            _disambiguateOperator(operatorIdentifier);
         return disambiguatedName; // Operators are not annotated.
 
       case SelectorKind.CALL:
         List<String> suffix = callSuffixForStructure(selector.callStructure);
         if (selector.name == Compiler.CALL_OPERATOR_NAME) {
           // Derive the annotated name for this variant of 'call'.
           return deriveCallMethodName(suffix);
         }
-        String disambiguatedName =
+        jsAst.Name disambiguatedName =
             _disambiguateMember(selector.memberName, suffix);
         return disambiguatedName; // Methods other than call are not annotated.
 
       default:
         compiler.internalError(compiler.currentElement,
             'Unexpected selector kind: ${selector.kind}');
         return null;
     }
   }
 
   /**
    * Returns the internal name used for an invocation mirror of this selector.
    */
-  String invocationMirrorInternalName(Selector selector)
+  jsAst.Name invocationMirrorInternalName(Selector selector)
       => invocationName(selector);
 
   /**
    * Returns the disambiguated name for the given field, used for constructing
    * the getter and setter names.
    */
-  String fieldAccessorName(FieldElement element) {
+  jsAst.Name fieldAccessorName(FieldElement element) {
     return element.isInstanceMember
         ? _disambiguateMember(element.memberName)
         : _disambiguateGlobal(element);
   }
 
   /**
    * Returns name of the JavaScript property used to store a static or instance
    * field.
    */
-  String fieldPropertyName(FieldElement element) {
+  jsAst.Name fieldPropertyName(FieldElement element) {
     return element.isInstanceMember
         ? instanceFieldPropertyName(element)
         : _disambiguateGlobal(element);
   }
 
   /**
    * Returns name of the JavaScript property used to store the
    * `readTypeVariable` function for the given type variable.
    */
-  String nameForReadTypeVariable(TypeVariableElement element) {
+  jsAst.Name nameForReadTypeVariable(TypeVariableElement element) {
     return _disambiguateInternalMember(element, () => element.name);
   }
 
   /**
    * Returns a JavaScript property name used to store [element] on one
    * of the global objects.
    *
    * Should be used together with [globalObjectFor], which denotes the object
    * on which the returned property name should be used.
    */
-  String globalPropertyName(Element element) {
+  jsAst.Name globalPropertyName(Element element) {
     return _disambiguateGlobal(element);
   }
 
   /**
    * Returns the JavaScript property name used to store an instance field.
    */
-  String instanceFieldPropertyName(FieldElement element) {
+  jsAst.Name instanceFieldPropertyName(FieldElement element) {
     ClassElement enclosingClass = element.enclosingClass;
 
     if (element.hasFixedBackendName) {
       // Certain native fields must be given a specific name. Native names must
       // not contain '$'. We rely on this to avoid clashes.
       assert(enclosingClass.isNative &&
              !element.fixedBackendName.contains(r'$'));
 
-      return element.fixedBackendName;
+      return new StringBackedName(element.fixedBackendName);
     }
 
     // Instances of BoxFieldElement are special. They are already created with
     // a unique and safe name. However, as boxes are not really instances of
     // classes, the usual naming scheme that tries to avoid name clashes with
     // super classes does not apply. We still do not mark the name as a
     // fixedBackendName, as we want to allow other namers to do something more
     // clever with them.
     if (element is BoxFieldElement) {
-      return element.name;
+      return new StringBackedName(element.name);
     }
 
     // If the name of the field might clash with another field,
     // use a mangled field name to avoid potential clashes.
     // Note that if the class extends a native class, that native class might
     // have fields with fixed backend names, so we assume the worst and always
     // mangle the field names of classes extending native classes.
     // Methods on such classes are stored on the interceptor, not the instance,
     // so only fields have the potential to clash with a native property name.
     ClassWorld classWorld = compiler.world;
@@ skipping 14 matching lines @@
     return element.enclosingClass.hasFieldShadowedBy(element);
   }
 
   /// True if [class_] is a non-native class that inherits from a native class.
   bool _isUserClassExtendingNative(ClassElement class_) {
     return !class_.isNative &&
            Elements.isNativeOrExtendsNative(class_.superclass);
   }
 
   /// Annotated name for the setter of [element].
-  String setterForElement(MemberElement element) {
+  jsAst.Name setterForElement(MemberElement element) {
     // We dynamically create setters from the field-name. The setter name must
     // therefore be derived from the instance field-name.
-    String name = _disambiguateMember(element.memberName);
+    jsAst.Name name = _disambiguateMember(element.memberName);
     return deriveSetterName(name);
   }
 
   /// Annotated name for the setter of any member with [disambiguatedName].
-  String deriveSetterName(String disambiguatedName) {
+  jsAst.Name deriveSetterName(jsAst.Name disambiguatedName) {
     // We dynamically create setters from the field-name. The setter name must
     // therefore be derived from the instance field-name.
-    return '$setterPrefix$disambiguatedName';
+    return new SetterName(new StringBackedName(setterPrefix),

[sra1, 2015/06/23 04:47:54]

The prefix should probably be cached.

[herhut, 2015/06/23 13:26:30]

Done.

+                          disambiguatedName);
   }
 
   /// Annotated name for the setter of any member with [disambiguatedName].
-  String deriveGetterName(String disambiguatedName) {
+  jsAst.Name deriveGetterName(jsAst.Name disambiguatedName) {
     // We dynamically create getters from the field-name. The getter name must
     // therefore be derived from the instance field-name.
-    return '$getterPrefix$disambiguatedName';
+    return new GetterName(new StringBackedName(getterPrefix),
+                          disambiguatedName);
   }
 
   /// Annotated name for the getter of [element].
-  String getterForElement(MemberElement element) {
+  jsAst.Name getterForElement(MemberElement element) {
     // We dynamically create getters from the field-name. The getter name must
     // therefore be derived from the instance field-name.
-    String name = _disambiguateMember(element.memberName);
+    jsAst.Name name = _disambiguateMember(element.memberName);
     return deriveGetterName(name);
   }
 
   /// Property name for the getter of an instance member with [originalName].
-  String getterForMember(Name originalName) {
-    String disambiguatedName = _disambiguateMember(originalName);
+  jsAst.Name getterForMember(Name originalName) {
+    jsAst.Name disambiguatedName = _disambiguateMember(originalName);
     return deriveGetterName(disambiguatedName);
   }
 
   /// Disambiguated name for a compiler-owned global variable.
   ///
   /// The resulting name is unique within the global-member namespace.
-  String _disambiguateInternalGlobal(String name) {
-    String newName = internalGlobals[name];
+  jsAst.Name _disambiguateInternalGlobal(String name) {
+    jsAst.Name newName = internalGlobals[name];
     if (newName == null) {
       newName = getFreshName(name, usedGlobalNames, suggestedGlobalNames);
       internalGlobals[name] = newName;
     }
     return newName;
   }
 
   /// Returns the property name to use for a compiler-owner global variable,
   /// i.e. one that does not correspond to any element but is used as a utility
   /// global by code generation.
   ///
   /// [name] functions as both the proposed name for the global, and as a key
   /// identifying the global. The [name] must not contain `$` symbols, since
   /// the [Namer] uses those names internally.
   ///
   /// This provides an easy mechanism of avoiding a name-clash with user-space
   /// globals, although the callers of must still take care not to accidentally
   /// pass in the same [name] for two different internal globals.
-  String internalGlobal(String name) {
+  jsAst.Name internalGlobal(String name) {
     assert(!name.contains(r'$'));
     return _disambiguateInternalGlobal(name);
   }
 
+  /// Generates a unique key for [library].
+  ///
+  /// Keys are meant to be used in maps and should not be visible in the output.
+  String _generateLibraryKey(LibraryElement library) {
+    return _libraryKeys.putIfAbsent(library, () {
+      String keyBase = library.name;
+      int counter = 0;
+      String key = keyBase;
+      while (_libraryKeys.values.contains(key)) {
+        key ="$keyBase${counter++}";
+      }
+      return key;
+    });
+  }
+
   /// Returns the disambiguated name for a top-level or static element.
   ///
   /// The resulting name is unique within the global-member namespace.
-  String _disambiguateGlobal(Element element) {
+  jsAst.Name _disambiguateGlobal(Element element) {
     // TODO(asgerf): We can reuse more short names if we disambiguate with
     // a separate namespace for each of the global holder objects.
     element = element.declaration;
-    String newName = userGlobals[element];
+    jsAst.Name newName = userGlobals[element];
     if (newName == null) {
       String proposedName = _proposeNameForGlobal(element);
       newName = getFreshName(proposedName, usedGlobalNames,
                              suggestedGlobalNames);
       userGlobals[element] = newName;
     }
     return newName;
   }
 
   /// Returns the disambiguated name for an instance method or field
   /// with [originalName] in [library].
   ///
   /// [library] may be `null` if [originalName] is known to be public.
   ///
   /// This is the name used for deriving property names of accessors (getters
   /// and setters) and as property name for storing methods and method stubs.
   ///
   /// [suffixes] denote an extension of [originalName] to distiguish it from
   /// other members with that name. These are used to encode the arity and
   /// named parameters to a method. Disambiguating the same [originalName] with
   /// different [suffixes] will yield different disambiguated names.
   ///
   /// The resulting name, and its associated annotated names, are unique
   /// to the ([originalName], [suffixes]) pair within the instance-member
   /// namespace.
-  String _disambiguateMember(Name originalName,
-                             [List<String> suffixes = const []]) {
+  jsAst.Name _disambiguateMember(Name originalName,
+                                 [List<String> suffixes = const []]) {
     // Build a string encoding the library name, if the name is private.
     String libraryKey = originalName.isPrivate
-            ? _disambiguateGlobal(originalName.library)
+            ? _generateLibraryKey(originalName.library)
             : '';
 
     // In the unique key, separate the name parts by '@'.
     // This avoids clashes since the original names cannot contain that symbol.
     String key = '$libraryKey@${originalName.text}@${suffixes.join('@')}';
-    String newName = userInstanceMembers[key];
+    jsAst.Name newName = userInstanceMembers[key];
     if (newName == null) {
       String proposedName = privateName(originalName);
       if (!suffixes.isEmpty) {
         // In the proposed name, separate the name parts by '$', because the
         // proposed name must be a valid identifier, but not necessarily unique.
         proposedName += r'$' + suffixes.join(r'$');
       }
       newName = getFreshName(proposedName,
                              usedInstanceNames, suggestedInstanceNames,
                              sanitizeForAnnotations: true);
@@ skipping 11 matching lines @@
   /// Using [_disambiguateMember] with the given [originalName] and no suffixes
   /// will subsequently return [disambiguatedName].
   void reservePublicMemberName(String originalName,
                                String disambiguatedName) {
     // Build a key that corresponds to the one built in disambiguateMember.
     String libraryPrefix = ''; // Public names have an empty library prefix.
     String suffix = ''; // We don't need any suffixes.
     String key = '$libraryPrefix@$originalName@$suffix';
     assert(!userInstanceMembers.containsKey(key));
     assert(!usedInstanceNames.contains(disambiguatedName));
-    userInstanceMembers[key] = disambiguatedName;
+    userInstanceMembers[key] = new StringBackedName(disambiguatedName);
     usedInstanceNames.add(disambiguatedName);
   }
 
   /// Disambiguated name unique to [element].
   ///
   /// This is used as the property name for fields, type variables,
   /// constructor bodies, and super-accessors.
   ///
   /// The resulting name is unique within the instance-member namespace.
-  String _disambiguateInternalMember(Element element, String proposeName()) {
-    String newName = internalInstanceMembers[element];
+  jsAst.Name _disambiguateInternalMember(Element element,
+                                         String proposeName()) {
+    jsAst.Name newName = internalInstanceMembers[element];
     if (newName == null) {
       String name = proposeName();
       bool mayClashNative = _isUserClassExtendingNative(element.enclosingClass);
       newName = getFreshName(name,
                              usedInstanceNames, suggestedInstanceNames,
                              sanitizeForAnnotations: true,
                              sanitizeForNatives: mayClashNative);
       internalInstanceMembers[element] = newName;
     }
     return newName;
   }
 
   /// Disambiguated name for the given operator.
   ///
   /// [operatorIdentifier] must be the operator's identifier, e.g.
   /// `$add` and not `+`.
   ///
   /// The resulting name is unique within the instance-member namespace.
-  String _disambiguateOperator(String operatorIdentifier) {
-    String newName = userInstanceOperators[operatorIdentifier];
+  jsAst.Name _disambiguateOperator(String operatorIdentifier) {
+    jsAst.Name newName = userInstanceOperators[operatorIdentifier];
     if (newName == null) {
       newName = getFreshName(operatorIdentifier, usedInstanceNames,
                              suggestedInstanceNames);
       userInstanceOperators[operatorIdentifier] = newName;
     }
     return newName;
   }
 
   /// Returns an unused name.
   ///
   /// [proposedName] must be a valid JavaScript identifier.
   ///
   /// If [sanitizeForAnnotations] is `true`, then the result is guaranteed not
   /// to have the form of an annotated name.
   ///
   /// If [sanitizeForNatives] it `true`, then the result is guaranteed not to
   /// clash with a property name on a native object.
   ///
   /// Note that [MinifyNamer] overrides this method with one that produces
   /// minified names.
-  String getFreshName(String proposedName,
-                      Set<String> usedNames,
-                      Map<String, String> suggestedNames,
-                      {bool sanitizeForAnnotations: false,
-                       bool sanitizeForNatives: false}) {
+  jsAst.Name getFreshName(String proposedName,
+                          Set<String> usedNames,
+                          Map<String, String> suggestedNames,
+                          {bool sanitizeForAnnotations: false,
+                           bool sanitizeForNatives: false}) {
     if (sanitizeForAnnotations) {
       proposedName = _sanitizeForAnnotations(proposedName);
     }
     if (sanitizeForNatives) {
       proposedName = _sanitizeForNatives(proposedName);
     }
     proposedName = _sanitizeForKeywords(proposedName);
     String candidate;
     if (!usedNames.contains(proposedName)) {
       candidate = proposedName;
     } else {
       int counter = popularNameCounters[proposedName];
       int i = (counter == null) ? 0 : counter;
       while (usedNames.contains("$proposedName$i")) {
         i++;
       }
       popularNameCounters[proposedName] = i + 1;
       candidate = "$proposedName$i";
     }
     usedNames.add(candidate);
-    return candidate;
+    return new StringBackedName(candidate);
   }
 
   /// Returns a variant of [name] that cannot clash with the annotated
   /// version of another name, that is, the resulting name can never be returned
   /// by [deriveGetterName], [deriveSetterName], [deriveCallMethodName],
   /// [operatorIs], or [substitutionName].
   ///
   /// For example, a name `get$x` would be converted to `$get$x` to ensure it
   /// cannot clash with the getter for `x`.
   ///
@@ skipping 45 matching lines @@
     } else if (Elements.isStaticOrTopLevel(element)) {
       if (element.isClassMember) {
         ClassElement enclosingClass = element.enclosingClass;
         name = "${enclosingClass.name}_"
                "${element.name}";
       } else {
         name = element.name.replaceAll('+', '_');
       }
     } else if (element.isLibrary) {
       LibraryElement library = element;
+      name = libraryLongNames[library];
+      if (name != null) return name;
       name = library.getLibraryOrScriptName();
       if (name.contains('.')) {
         // For libraries that have a library tag, we use the last part
         // of the fully qualified name as their base name. For all other
         // libraries, we use the first part of their filename.
         name = library.hasLibraryName()
             ? name.substring(name.lastIndexOf('.') + 1)
             : name.substring(0, name.indexOf('.'));
       }
       // The filename based name can contain all kinds of nasty characters. Make
       // sure it is an identifier.
       if (!IDENTIFIER.hasMatch(name)) {
         name = name.replaceAllMapped(NON_IDENTIFIER_CHAR,
             (match) => match[0].codeUnitAt(0).toRadixString(16));
         if (!IDENTIFIER.hasMatch(name)) {  // e.g. starts with digit.
           name = 'lib_$name';
         }
       }
+      // Names constructed based on a libary name will be further disambiguated.
+      // However, as names from the same libary should have the same libary
+      // name part, we disambiguate the library name here.
+      String disambiguated  = name;
+      for (int c = 0; libraryLongNames.containsValue(disambiguated); c++) {
+        disambiguated = "$name$c";
+      }
+      libraryLongNames[library] = disambiguated;
+      name = disambiguated;
     } else {
       name = element.name;
     }
     return name;
   }
 
   String suffixForGetInterceptor(Iterable<ClassElement> classes) {
     String abbreviate(ClassElement cls) {
       if (cls == compiler.objectClass) return "o";
       if (cls == backend.jsStringClass) return "s";
@@ skipping 14 matching lines @@
     if (classes.any((cls) => Elements.isNativeOrExtendsNative(cls))) {
       names.add("x");
     }
     // Sort the names of the classes after abbreviating them to ensure
     // the suffix is stable and predictable for the suggested names.
     names.sort();
     return names.join();
   }
 
   /// Property name used for `getInterceptor` or one of its specializations.
-  String nameForGetInterceptor(Iterable<ClassElement> classes) {
+  jsAst.Name nameForGetInterceptor(Iterable<ClassElement> classes) {
     FunctionElement getInterceptor = backend.getInterceptorMethod;
     if (classes.contains(backend.jsInterceptorClass)) {
       // If the base Interceptor class is in the set of intercepted classes, we
       // need to go through the generic getInterceptorMethod, since any subclass
       // of the base Interceptor could match.
       // The unspecialized getInterceptor method can also be accessed through
       // its element, so we treat this as a user-space global instead of an
       // internal global.
       return _disambiguateGlobal(getInterceptor);
     }
     String suffix = suffixForGetInterceptor(classes);
     return _disambiguateInternalGlobal("${getInterceptor.name}\$$suffix");
   }
 
   /// Property name used for the one-shot interceptor method for the given
   /// [selector] and return-type specialization.
-  String nameForGetOneShotInterceptor(Selector selector,
-                                      Iterable<ClassElement> classes) {
+  jsAst.Name nameForGetOneShotInterceptor(Selector selector,
+                                          Iterable<ClassElement> classes) {
     // The one-shot name is a global name derived from the invocation name.  To
     // avoid instability we would like the names to be unique and not clash with
     // other global names.
 
-    String root = invocationName(selector);
+    jsAst.Name root = invocationName(selector);
 
     if (classes.contains(backend.jsInterceptorClass)) {
       // If the base Interceptor class is in the set of intercepted classes,
       // this is the most general specialization which uses the generic
       // getInterceptor method.  To keep the name short, we add '$' only to
       // distinguish from internal globals requested from outside the Namer
       // with internalGlobal().
       // TODO(sra): Find a way to get the simple name when Object is not in the
       // set of classes for most general variant, e.g. "$lt$n" could be "$lt".
-      if (selector.isGetter || selector.isSetter) root = '$root\$';
-      return _disambiguateInternalGlobal(root);
+    if (selector.isGetter || selector.isSetter) {
+      return new CompoundName([root, literalDollar]);
+    } else {
+      return root;
+    }
     } else {
       String suffix = suffixForGetInterceptor(classes);
-      return _disambiguateInternalGlobal("$root\$$suffix");
+      return new CompoundName([root, literalDollar,
+                               new StringBackedName(suffix)]);
     }
   }
 
   /// Returns the runtime name for [element].
   ///
   /// This name is used as the basis for deriving `is` and `as` property names
   /// for the given type.
   ///
   /// The result is not always safe as a property name unless prefixing
   /// [operatorIsPrefix] or [operatorAsPrefix]. If this is a function type,
   /// then by convention, an underscore must also separate [operatorIsPrefix]
   /// from the type name.
-  String runtimeTypeName(TypeDeclarationElement element) {
-    if (element == null) return 'dynamic';
+  jsAst.Name runtimeTypeName(TypeDeclarationElement element) {
+    if (element == null) return literalDynamic;
     // The returned name affects both the global and instance member namespaces:
     //
     // - If given a class, this must coincide with the class name, which
     //   is also the GLOBAL property name of its constructor.
     //
     // - The result is used to derive `$isX` and `$asX` names, which are used
     //   as INSTANCE property names.
     //
     // To prevent clashes in both namespaces at once, we disambiguate the name
     // as a global here, and in [_sanitizeForAnnotations] we ensure that
     // ordinary instance members cannot start with `$is` or `$as`.
     return _disambiguateGlobal(element);
   }
 
   /// Returns the disambiguated name of [class_].
   ///
   /// This is both the *runtime type* of the class (see [runtimeTypeName])
   /// and a global property name in which to store its JS constructor.
-  String className(ClassElement class_) => _disambiguateGlobal(class_);
+  jsAst.Name className(ClassElement class_) => _disambiguateGlobal(class_);
 
   /// Property name on which [member] can be accessed directly,
   /// without clashing with another JS property name.
   ///
   /// This is used for implementing super-calls, where ordinary dispatch
   /// semantics must be circumvented. For example:
   ///
   ///     class A { foo() }
   ///     class B extends A {
   ///         foo() { super.foo() }
   ///     }
   ///
   /// Example translation to JS:
   ///
   ///     A.prototype.super$A$foo = function() {...}
   ///     A.prototype.foo$0 = A.prototype.super$A$foo
   ///
   ///     B.prototype.foo$0 = function() {
   ///         this.super$A$foo(); // super.foo()
   ///     }
   ///
-  String aliasedSuperMemberPropertyName(Element member) {
+  jsAst.Name aliasedSuperMemberPropertyName(Element member) {
     assert(!member.isField); // Fields do not need super aliases.
-    String methodName = instanceMethodName(member);
-    return _disambiguateInternalMember(member,
-        () => 'super\$${member.enclosingClass.name}\$$methodName');
+    return _disambiguateInternalMember(member, () {
+      String invocationName = operatorNameToIdentifier(member.name);
+      return "super\$${member.enclosingClass.name}\$$invocationName";
+    });
   }
 
   /// Property name in which to store the given static or instance [method].
   /// For instance methods, this includes the suffix encoding arity and named
   /// parameters.
   ///
   /// The name is not necessarily unique to [method], since a static method
   /// may share its name with an instance method.
-  String methodPropertyName(Element method) {
+  jsAst.Name methodPropertyName(Element method) {
     return method.isInstanceMember
         ? instanceMethodName(method)
         : globalPropertyName(method);
   }
 
   /// Returns true if [element] is stored on current isolate ('$').  We intend
   /// to store only mutable static state in [currentIsolate], constants are
   /// stored in 'C', and functions, accessors, classes, etc. are stored in one
   /// of the other objects in [reservedGlobalObjectNames].
   bool isPropertyOfCurrentIsolate(Element element) {
@@ skipping 18 matching lines @@
     if (library == backend.interceptorsLibrary) return 'J';
     if (library.isInternalLibrary) return 'H';
     if (library.isPlatformLibrary) {
       if ('${library.canonicalUri}' == 'dart:html') return 'W';
       return 'P';
     }
     return userGlobalObjects[
         library.getLibraryOrScriptName().hashCode % userGlobalObjects.length];
   }
 
-  String lazyInitializerName(Element element) {
+  jsAst.Name lazyInitializerName(Element element) {
     assert(Elements.isStaticOrTopLevelField(element));
-    String name = _disambiguateGlobal(element);
-    return _disambiguateInternalGlobal("$getterPrefix$name");
+    jsAst.Name name = _disambiguateGlobal(element);
+    // Why do we need to disambiguate here?

[floitsch, 2015/06/22 17:43:44]

Maybe I'm missing something, but I think you can have:

    // on top-level:
    var get$myglobal = 0;
    var myglobal = new Foo();

the get$myglobal will be disambiguated to "get$myglobal".
if we just went ahead and derived the getter-name from myglobal it would clash
with the other variable.

This wouldn't be the case for instance variables where we pay more attention.

[herhut, 2015/06/23 13:26:30]

Good point. Fixed.

+    // return _disambiguateInternalGlobal("$getterPrefix$name");
+    return deriveGetterName(name);
   }
 
-  String staticClosureName(Element element) {
+  jsAst.Name staticClosureName(Element element) {
     assert(Elements.isStaticOrTopLevelFunction(element));
-    String name = _disambiguateGlobal(element);
-    return _disambiguateInternalGlobal("$name\$closure");
+    String enclosing = element.enclosingClass == null
+        ? "" : element.enclosingClass.name;
+    String library = _proposeNameForGlobal(element.library);
+    return _disambiguateInternalGlobal(
+        "${library}_${enclosing}_${element.name}\$closure");
   }
 
   // This name is used as part of the name of a TypeConstant
   String uniqueNameForTypeConstantElement(Element element) {
     // TODO(sra): If we replace the period with an identifier character,
     // TypeConstants will have better names in unminified code.
-    return "${globalObjectFor(element)}.${globalPropertyName(element)}";
+    String library = _proposeNameForGlobal(element.library);
+    return "${library}.${element.name}";
   }
 
   String globalObjectForConstant(ConstantValue constant) => 'C';
 
   String get operatorIsPrefix => r'$is';
 
   String get operatorAsPrefix => r'$as';
 
   String get operatorSignature => r'$signature';
 
   String get typedefTag => r'typedef';
 
   String get functionTypeTag => r'func';
 
   String get functionTypeVoidReturnTag => r'void';
 
   String get functionTypeReturnTypeTag => r'ret';
 
   String get functionTypeRequiredParametersTag => r'args';
 
   String get functionTypeOptionalParametersTag => r'opt';
 
   String get functionTypeNamedParametersTag => r'named';
 
-  Map<FunctionType,String> functionTypeNameMap =
-      new Map<FunctionType,String>();
+  Map<FunctionType, jsAst.Name> functionTypeNameMap =
+      new HashMap<FunctionType, jsAst.Name>();
   final FunctionTypeNamer functionTypeNamer;
 
-  String getFunctionTypeName(FunctionType functionType) {
+  jsAst.Name getFunctionTypeName(FunctionType functionType) {
     return functionTypeNameMap.putIfAbsent(functionType, () {
       String proposedName = functionTypeNamer.computeName(functionType);
-      String freshName = getFreshName(proposedName, usedInstanceNames,
-                                      suggestedInstanceNames);
-      return freshName;
+      return getFreshName(proposedName, usedInstanceNames,
+                          suggestedInstanceNames);
     });
   }
 
-  String operatorIsType(DartType type) {
+  jsAst.Name operatorIsType(DartType type) {
     if (type.isFunctionType) {
       // TODO(erikcorry): Reduce from $isx to ix when we are minifying.
-      return '${operatorIsPrefix}_${getFunctionTypeName(type)}';
+      return new CompoundName([new StringBackedName(operatorIsPrefix),
+                               literalUnderscore,
+                               getFunctionTypeName(type)]);
     }
     return operatorIs(type.element);
   }
 
-  String operatorIs(ClassElement element) {
+  jsAst.Name operatorIs(ClassElement element) {
     // TODO(erikcorry): Reduce from $isx to ix when we are minifying.
-    return '${operatorIsPrefix}${runtimeTypeName(element)}';
+    return new CompoundName([new StringBackedName(operatorIsPrefix),
+                             runtimeTypeName(element)]);
   }
 
   /// Returns a name that does not clash with reserved JS keywords.
   String _sanitizeForKeywords(String name) {
     if (jsReserved.contains(name)) {
       name = '\$$name';
     }
     assert(!jsReserved.contains(name));
     return name;
   }
 
-  String substitutionName(Element element) {
-    return '${operatorAsPrefix}${runtimeTypeName(element)}';
+  jsAst.Name substitutionName(Element element) {
+    return new CompoundName([new StringBackedName(operatorAsPrefix),
+                             runtimeTypeName(element)]);
+  }
+
+  /// Translates a [String] into the corresponding [Name] data structure as
+  /// used by the namer.
+  ///
+  /// If [name] is a setter or getter name, the corresponding [GetterName] or

[floitsch, 2015/06/22 17:43:44]

That shouldn't be necessary for static names. (unless mirrors depend on it).

[herhut, 2015/06/23 13:26:30]

This is mostly used in testing (as otherwise one cannot test for the right names
to be emitted). By how == is defined, we have to construct 'getternames' in the
right way.

+  /// [SetterName] data structure is used.
+  jsAst.Name asName(String name) {
+    if (name.startsWith(getterPrefix) && name.length > getterPrefix.length) {
+      return new GetterName(new StringBackedName(getterPrefix),
+                           new StringBackedName(
+                               name.substring(getterPrefix.length)));
+    }
+    if (name.startsWith(setterPrefix) && name.length > setterPrefix.length) {
+      return new GetterName(new StringBackedName(setterPrefix),
+                            new StringBackedName(
+                                name.substring(setterPrefix.length)));
+    }
+
+    return new StringBackedName(name);
   }
 
   /// Returns a variable name that cannot clash with a keyword, a global
   /// variable, or any name starting with a single '$'.
   ///
   /// Furthermore, this function is injective, that is, it never returns the
   /// same name for two different inputs.
   String safeVariableName(String name) {
     if (jsVariableReserved.contains(name) || name.startsWith(r'$')) {
       return '\$$name';
@@ skipping 48 matching lines @@
     }
   }
 
   String get incrementalHelperName => r'$dart_unsafe_incremental_support';
 
   jsAst.Expression get accessIncrementalHelper {
     return js('self.${incrementalHelperName}');
   }
 
   void forgetElement(Element element) {
-    String globalName = userGlobals[element];
+    jsAst.Name globalName = userGlobals[element];
     invariant(element, globalName != null, message: 'No global name.');
     usedGlobalNames.remove(globalName);
     userGlobals.remove(element);
   }
 }
 
+abstract class _NamerName extends jsAst.Name {
+  int get _kind;
+}
+
+class StringBackedName extends _NamerName {
+  final String name;
+  final int _kind = 1;

[sra1, 2015/06/23 04:47:54]

int get _kind => 1;

Otherwise you are still doing virtual dispatch to load a field.

[herhut, 2015/06/23 13:26:30]

Done.

+  
+  StringBackedName(this.name);
+
+  toString() => throw new UnsupportedError("Cannot convert a name to a string");
+
+  operator==(other) => (other is StringBackedName) && other.name == name;

[sra1, 2015/06/23 04:47:54]

Is the purpose of  ==, hashCode and compareTo?
Are == and hashCode make a Name possible as a hash table key?

Is compareTo for a specific order or arbitrary order?

I think it must be an arbitrary but stable order since it is used to order the
assignments to getInterceptor specializations, which will happen before you can
do a frequency based name assignment.  You must assume that two names with
different derivations will have different final names.

Please document that compareTo is arbitrary but consistent.


The nsm delta table requires lexicographic ordering. This is is completely
different. This is the 'same fringe' problem which can be solved with a codeUnit
iterator.
At that point you might as well simply sort by full name.

[herhut, 2015/06/23 13:26:30]

Yes. However, typically only instances of StingBackedName are used in HashMaps
and Sets, to the cost for CompoundName can be tolerated.
Yes, they are sorted in some consistent order. Which one does not really matter
in cases where it is about stability only. 
Done in the js_ast package.
While this namer could do full name sorting, a frequency based one cannot do it
on the name tokens. I wanted to have both behave the same way, so that I only
need to replace StringBackedName and keep all the rest as is.

In the nsm emitter, I now sort as it was before yet on the actual names when
printing.

+
+  int get hashCode => name.hashCode;
+
+  int compareTo(other) {
+    if (other is! _NamerName) return -1;

[sra1, 2015/06/23 04:47:54]

Since you can't make the other implementation of Name honour this by returning
'1',
please make this an assertion or type assertion.

[herhut, 2015/06/23 13:26:30]

Done.

+    if (other._kind != _kind) return other._kind - _kind;
+    return name.compareTo(other.name);
+  }
+}
+
+abstract class _PrefixedName extends _NamerName {
+  final jsAst.Name prefix;
+  final jsAst.Name base;
+  int get _kind;

[sra1, 2015/06/23 04:47:54]

Somewhat redundant with _NamerName._kind.
Leave it here if you want.

[herhut, 2015/06/23 13:26:31]

Removed.

+
+  _PrefixedName(this.prefix, this.base);
+  
+  String get name => prefix.name + base.name;
+
+  toString() => throw new UnsupportedError("Cannot convert a name to a string");
+
+  operator==(other) {
+    if (other is! _PrefixedName) return false;
+    return other.base == base && other.prefix == prefix;
+  }
+
+  int get hashCode => base.hashCode * 13 + prefix.hashCode;
+
+  int compareTo(other) {
+    if (other is! _NamerName) return -1;
+    if (other._kind != _kind) return other._kind - _kind;
+    int result = prefix.compareTo(other.prefix);
+    if (result == 0) {
+      result = name.compareTo(other.name);
+    }
+    return result;
+  }
+}
+
+class GetterName extends _PrefixedName {
+  final int _kind = 2;
+
+  GetterName(jsAst.Name prefix, jsAst.Name base) : super(prefix, base);
+}
+
+class SetterName extends _PrefixedName {
+  final int _kind = 3;
+
+  SetterName(jsAst.Name prefix, jsAst.Name base) : super(prefix, base);
+}
+
+class CompoundName extends _NamerName {
+  final List<_NamerName> _parts;
+  final int _kind = 4;
+  String _cachedName;
+  int _cachedHashCode = -1;
+
+  CompoundName(this._parts);
+
+  String get name {
+    if (_cachedName == null) {
+      _cachedName = _parts.map((jsAst.Name name) => name.name).join();
+    }
+    return _cachedName;
+  }
+
+  toString() => throw new UnsupportedError("Cannot convert a name to a string");
+
+  operator==(other) {

[floitsch, 2015/06/22 17:43:44]

bool 

[herhut, 2015/06/23 13:26:31]

Done.

+    if (other is! CompoundName) return false;
+    if (other._parts.length != _parts.length) return false;
+    for (int i = 0; i < _parts.length; ++i) {
+      if (other._parts[i] != _parts[i]) return false;
+    }
+    return true;
+  }
+
+  int get hashCode {
+    if (_cachedHashCode < 0) {
+      _cachedHashCode = 0;
+      for (jsAst.Name name in _parts) {
+        _cachedHashCode = (_cachedHashCode * 17) & 0x7fffffff;
+      }
+    }
+    return _cachedHashCode;
+  }
+
+  int compareTo(other) {
+    if (other is! _NamerName) return -1;
+    if (other._kind != _kind) return other._kind - _kind;
+    if (other._parts.length != _parts.length) {
+      return other._parts.length - _parts.length;
+    }
+    int result = 0;
+    for (int pos = 0; result == 0 && pos < _parts.length; pos++) {
+      result = _parts[pos].compareTo(other._parts[pos]);
+    }
+    return result;
+  }
+}
+
 /**
  * Generator of names for [ConstantValue] values.
  *
  * The names are stable under perturbations of the source.  The name is either a
  * short sequence of words, if this can be found from the constant, or a type
  * followed by a hash tag.
  *
  *     List_imX                // A List, with hash tag.
  *     C_Sentinel              // const Sentinel(),  "C_" added to avoid clash
  *                             //   with class name.
@@ skipping 164 matching lines @@
 
   @override
   void visitSynthetic(SyntheticConstantValue constant, [_]) {
     switch (constant.kind) {
       case SyntheticConstantKind.DUMMY_INTERCEPTOR:
         add('dummy_receiver');
         break;
       case SyntheticConstantKind.TYPEVARIABLE_REFERENCE:
         add('type_variable_reference');
         break;
+      case SyntheticConstantKind.NAME:
+        add('name');
+        break;
       default:
         compiler.internalError(compiler.currentElement,
                                "Unexpected SyntheticConstantValue");
     }
   }
 
   @override
   void visitDeferred(DeferredConstantValue constant, [_]) {
     addRoot('Deferred');
   }
@@ skipping 228 matching lines @@
         if (!first) {
           sb.write('_');
         }
         sb.write('_');
         visit(parameter);
         first = true;
       }
     }
   }
 }