Move Entity and Local to entities.dart

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

Index: pkg/compiler/lib/src/elements/entities.dart
diff --git a/pkg/compiler/lib/src/elements/entities.dart b/pkg/compiler/lib/src/elements/entities.dart
index 7d45c4a998403fed4e1d3c2d1ac34843f3f30cef..14a3b386e0d532ad4e68039acf950bb67f2708f6 100644
--- a/pkg/compiler/lib/src/elements/entities.dart
+++ b/pkg/compiler/lib/src/elements/entities.dart
@@ -4,7 +4,20 @@
 
 library entities;
 
-import 'elements.dart' show Entity;
+import '../common.dart';
+
+/// Abstract interface for entities.
+///
+/// Implement this directly if the entity is not a Dart language entity.
+/// Entities defined within the Dart language should implement [Element].
+///
+/// For instance, the JavaScript backend need to create synthetic variables for
+/// calling intercepted classes and such variables do not correspond to an
+/// entity in the Dart source code nor in the terminology of the Dart language
+/// and should therefore implement [Entity] directly.
+abstract class Entity implements Spannable {
+  String get name;
+}
 
 /// Stripped down super interface for library like entities.
 ///
@@ -67,3 +80,27 @@ abstract class ConstructorEntity extends FunctionEntity {
   bool get isGenerativeConstructor;
   bool get isFactoryConstructor;
 }
+
+/// An entity that defines a local entity (memory slot) in generated code.
+///
+/// Parameters, local variables and local functions (can) define local entity
+/// and thus implement [Local] through [LocalElement]. For non-element locals,
+/// like `this` and boxes, specialized [Local] classes are created.
+///
+/// Type variables can introduce locals in factories and constructors
+/// but since one type variable can introduce different locals in different
+/// factories and constructors it is not itself a [Local] but instead
+/// a non-element [Local] is created through a specialized class.
+// TODO(johnniwinther): Should [Local] have `isAssignable` or `type`?
+abstract class Local extends Entity {
+  /// The context in which this local is defined.
+  Entity get executableContext;
+
+  /// The outermost member that contains this element.
+  ///
+  /// For top level, static or instance members, the member context is the
+  /// element itself. For parameters, local variables and nested closures, the
+  /// member context is the top level, static or instance member in which it is
+  /// defined.
+  MemberEntity get memberContext;
+}