Use entities in Selector methods

pkg/compiler/lib/src/elements/entities.dart

 // Copyright (c) 2016, 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 entities;
 
 import '../common.dart';
 
 /// Abstract interface for entities.
 ///
@@ skipping 68 matching lines @@
   /// Whether this is a normal method (neither constructor, getter or setter)
   /// or operator method.
   bool get isFunction;
 
   /// Whether this is a getter.
   bool get isGetter;
 
   /// Whether this is a setter.
   bool get isSetter;
 
-  /// Whether this member is assignable, i.e. a non-final field.
+  /// Whether this member is assignable, i.e. a non-final, non-const field.
   bool get isAssignable;
 
   /// Whether this member is constant, i.e. a constant field or constructor.
   bool get isConst;
 
   /// Whether this member is abstract, i.e. an abstract method, getter or
   /// setter.
   bool get isAbstract;
 
   /// The enclosing class if this is a constructor, instance member or
@@ skipping 77 matching lines @@
       this.requiredParameters, this.positionalParameters, this.namedParameters);
 
   const ParameterStructure.getter() : this(0, 0, const <String>[]);
 
   const ParameterStructure.setter() : this(1, 1, const <String>[]);
 
   /// The number of optional parameters (positional or named).
   int get optionalParameters =>
       positionalParameters - requiredParameters + namedParameters.length;
 }