dart2js: Extract minified field naming into mixin.

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

Index: pkg/compiler/lib/src/js_backend/minify_namer.dart
diff --git a/pkg/compiler/lib/src/js_backend/minify_namer.dart b/pkg/compiler/lib/src/js_backend/minify_namer.dart
index 2f0b37cac60070b4876a3399e3717047d6a2817b..9a2d1e3fc4a1290eb5a086a1cceeaae5933d20fe 100644
--- a/pkg/compiler/lib/src/js_backend/minify_namer.dart
+++ b/pkg/compiler/lib/src/js_backend/minify_namer.dart
@@ -7,12 +7,14 @@ part of js_backend;
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
-class MinifyNamer extends Namer {
+class MinifyNamer extends Namer with _MinifiedFieldNamer {
   MinifyNamer(Compiler compiler) : super(compiler) {
     reserveBackendNames();
     fieldRegistry = new _FieldNamingRegistry(this);
   }
 
+  _FieldNamingRegistry fieldRegistry;
+
   String get isolateName => 'I';
   String get isolatePropertiesName => 'p';
   bool get shouldMinify => true;
@@ -24,18 +26,17 @@ class MinifyNamer extends Namer {
   final ALPHABET_CHARACTERS = 52;  // a-zA-Z.
   final ALPHANUMERIC_CHARACTERS = 62;  // a-zA-Z0-9.
 
-  _FieldNamingRegistry fieldRegistry;
-
   /// You can pass an invalid identifier to this and unlike its non-minifying
   /// counterpart it will never return the proposedName as the new fresh name.
   ///
   /// [sanitizeForNatives] and [sanitizeForAnnotations] are ignored because the
   /// minified names will always avoid clashing with annotated names or natives.
+  @override
   jsAst.Name getFreshName(String proposedName,
-                             Set<String> usedNames,
-                             Map<String, String> suggestedNames,
-                             {bool sanitizeForNatives: false,
-                              bool sanitizeForAnnotations: false}) {
+                          Set<String> usedNames,
+                          Map<String, String> suggestedNames,
+                          {bool sanitizeForNatives: false,
+                           bool sanitizeForAnnotations: false}) {
     String freshName;
     String suggestion = suggestedNames[proposedName];
     if (suggestion != null && !usedNames.contains(suggestion)) {
@@ -244,209 +245,13 @@ class MinifyNamer extends Namer {
     return $0 + x - 52;
   }
 
+  @override
   jsAst.Name instanceFieldPropertyName(Element element) {
-    if (element.hasFixedBackendName) {
-      return new StringBackedName(element.fixedBackendName);
-    }
-
-    _FieldNamingScope names;
-    if (element is BoxFieldElement) {
-      names = new _FieldNamingScope.forBox(element.box, fieldRegistry);
-    } else {
-      ClassElement cls = element is ClosureFieldElement
-          ? element.closureClass : element.enclosingClass;
-      names = new _FieldNamingScope.forClass(cls, compiler.world,
-          fieldRegistry);
-    }
-
-    // The inheritance scope based naming did not yield a name. For instance,
-    // this could be because the field belongs to a mixin.
-    if (!names.containsField(element)) {
-      return super.instanceFieldPropertyName(element);
-    }
-
-    return names[element];
-  }
-}
-
-/**
- * Encapsulates the global state of field naming.
- */
-class _FieldNamingRegistry {
-  final MinifyNamer namer;
-
-  final Map<Entity, _FieldNamingScope> scopes =
-      new Map<Entity, _FieldNamingScope>();
-
-  final Map<Entity, jsAst.Name> globalNames = new Map<Entity, jsAst.Name>();
-
-  int globalCount = 0;
-
-  final List<jsAst.Name> nameStore = new List<jsAst.Name>();
-
-  _FieldNamingRegistry(this.namer);
-
-  jsAst.Name getName(int count) {
-    if (count >= nameStore.length) {
-      // The namer usually does not use certain names as they clash with
-      // existing properties on JS objects (see [_reservedNativeProperties]).
-      // However, some of them are really short and safe to use for fields.
-      // Thus, we shortcut the namer to use those first.
-      if (count < MinifyNamer._reservedNativeProperties.length &&
-          MinifyNamer._reservedNativeProperties[count].length <= 2) {
-        nameStore.add(new StringBackedName(
-            MinifyNamer._reservedNativeProperties[count]));
-      } else {
-        nameStore.add(namer.getFreshName("field$count",
-            namer.usedInstanceNames, namer.suggestedInstanceNames));
-      }
-    }
-
-    return nameStore[count];
-  }
-}
-
-/**
- * A [_FieldNamingScope] encodes a node in the inheritance tree of the current
- * class hierarchy. The root node typically is the node corresponding to the
- * `Object` class. It is used to assign a unique name to each field of a class.
- * Unique here means unique wrt. all fields along the path back to the root.
- * This is achieved at construction time via the [_fieldNameCounter] field that
- * counts the number of fields on the path to the root node that have been
- * encountered so far.
- *
- * Obviously, this only works if no fields are added to a parent node after its
- * children have added their first field.
- */
-class _FieldNamingScope {
-  final _FieldNamingScope superScope;
-  final Entity container;
-  final Map<Element, jsAst.Name> names = new Maplet<Element, jsAst.Name>();
-  final _FieldNamingRegistry registry;
-
-  /// Naming counter used for fields of ordinary classes.
-  int _fieldNameCounter;
-
-  /// The number of fields along the superclass chain that use inheritance
-  /// based naming, including the ones allocated for this scope.
-  int get inheritanceBasedFieldNameCounter => _fieldNameCounter;
-
-  /// The number of locally used fields. Depending on the naming source
-  /// (e.g. inheritance based or globally unique for mixixns) this
-  /// might be different from [inheritanceBasedFieldNameCounter].
-  int get _localFieldNameCounter => _fieldNameCounter;
-  void set _localFieldNameCounter(int val) { _fieldNameCounter = val; }
-
-  factory _FieldNamingScope.forClass(ClassElement cls, ClassWorld world,
-      _FieldNamingRegistry registry) {
-    _FieldNamingScope result = registry.scopes[cls];
-    if (result != null) return result;
-
-    if (world.isUsedAsMixin(cls)) {
-      result = new _MixinFieldNamingScope.mixin(cls, registry);
-    } else {
-      if (cls.superclass == null) {
-        result = new _FieldNamingScope.rootScope(cls, registry);
-      } else {
-        _FieldNamingScope superScope = new _FieldNamingScope.forClass(
-            cls.superclass, world, registry);
-        if (cls.isMixinApplication) {
-          result = new _MixinFieldNamingScope.mixedIn(cls, superScope,
-              registry);
-        } else {
-          result = new _FieldNamingScope.inherit(cls, superScope, registry);
-        }
-      }
+    jsAst.Name proposed = _minifiedInstanceFieldPropertyName(element);
+    if (proposed != null) {
+      return proposed;
     }
-
-    cls.forEachInstanceField((cls, field) => result.add(field));
-
-    registry.scopes[cls] = result;
-    return result;
-  }
-
-  factory _FieldNamingScope.forBox(Local box, _FieldNamingRegistry registry) {
-    return registry.scopes.putIfAbsent(box,
-        () => new _BoxFieldNamingScope(box, registry));
-  }
-
-  _FieldNamingScope.rootScope(this.container, this.registry)
-    : superScope = null,
-      _fieldNameCounter = 0;
-
-  _FieldNamingScope.inherit(this.container, this.superScope, this.registry) {
-    _fieldNameCounter = superScope.inheritanceBasedFieldNameCounter;
-  }
-
-  /**
-   * Checks whether [name] is already used in the current scope chain.
-   */
-  _isNameUnused(jsAst.Name name) {
-    return !names.values.contains(name) &&
-        ((superScope == null) || superScope._isNameUnused(name));
+    return super.instanceFieldPropertyName(element);
   }
-
-  jsAst.Name _nextName() => registry.getName(_localFieldNameCounter++);
-
-  jsAst.Name operator[](Element field) {
-    jsAst.Name name = names[field];
-    if (name == null && superScope != null) return superScope[field];
-    return name;
-  }
-
-  void add(Element field) {
-    if (names.containsKey(field)) return;
-
-    jsAst.Name value = _nextName();
-    assert(invariant(field, _isNameUnused(value)));
-    names[field] = value;
-  }
-
-  bool containsField(Element field) => names.containsKey(field);
 }
 
-/**
- * Field names for mixins have two constraints: They need to be unique in the
- * hierarchy of each application of a mixin and they need to be the same for
- * all applications of a mixin. To achieve this, we use global naming for
- * mixins from the same name pool as fields and add a `$` at the end to ensure
- * they do not collide with normal field names. The `$` sign is typically used
- * as a separator between method names and argument counts and does not appear
- * in generated names themselves.
- */
-class _MixinFieldNamingScope extends _FieldNamingScope {
-  int get _localFieldNameCounter => registry.globalCount;
-  void set _localFieldNameCounter(int val) { registry.globalCount = val; }
-
-  Map<Entity, jsAst.Name> get names => registry.globalNames;
-
-  _MixinFieldNamingScope.mixin(ClassElement cls, _FieldNamingRegistry registry)
-    : super.rootScope(cls, registry);
-
-  _MixinFieldNamingScope.mixedIn(MixinApplicationElement container,
-      _FieldNamingScope superScope, _FieldNamingRegistry registry)
-    : super.inherit(container, superScope, registry);
-
-  jsAst.Name _nextName() {
-    jsAst.Name proposed = super._nextName();
-    return new CompoundName([proposed, Namer._literalDollar]);
-  }
-}
-
-/**
- * [BoxFieldElement] fields work differently in that they do not belong to an
- * actual class but an anonymous box associated to a [Local]. As there is no
- * inheritance chain, we do not need to compute fields a priori but can assign
- * names on the fly.
- */
-class _BoxFieldNamingScope extends _FieldNamingScope {
-  _BoxFieldNamingScope(Local box, _FieldNamingRegistry registry) :
-    super.rootScope(box, registry);
-
-  bool containsField(_) => true;
-
-  jsAst.Name operator[](Element field) {
-    if (!names.containsKey(field)) add(field);
-    return names[field];
-  }
-}