Add FunctionEntity.asyncMarker and refactor SourceInformationStrategy to avoid ResolvedAst

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 'package:front_end/src/fasta/parser/async_modifier.dart'
+    show AsyncModifier;
+
 import '../common.dart';
 import '../universe/call_structure.dart' show CallStructure;
 
 /// 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
@@ skipping 99 matching lines @@
 ///
 /// Currently only [MethodElement] but later also kernel based Dart constructors
 /// and methods and/or Dart-in-JS function-like properties.
 abstract class FunctionEntity extends MemberEntity {
   /// Whether this function is external, i.e. the body is not defined in terms
   /// of Dart code.
   bool get isExternal;
 
   /// The structure of the function parameters.
   ParameterStructure get parameterStructure;
+
+  /// The synchronous/asynchronous marker on this function.
+  AsyncMarker get asyncMarker;
+}
+
+/// Enum for the synchronous/asynchronous function body modifiers.
+class AsyncMarker {
+  /// The default function body marker.
+  static const AsyncMarker SYNC = const AsyncMarker._(AsyncModifier.Sync);
+
+  /// The `sync*` function body marker.
+  static const AsyncMarker SYNC_STAR =
+      const AsyncMarker._(AsyncModifier.SyncStar, isYielding: true);
+
+  /// The `async` function body marker.
+  static const AsyncMarker ASYNC =
+      const AsyncMarker._(AsyncModifier.Async, isAsync: true);
+
+  /// The `async*` function body marker.
+  static const AsyncMarker ASYNC_STAR = const AsyncMarker._(
+      AsyncModifier.AsyncStar,
+      isAsync: true,
+      isYielding: true);
+
+  /// Is `true` if this marker defines the function body to have an
+  /// asynchronous result, that is, either a [Future] or a [Stream].
+  final bool isAsync;
+
+  /// Is `true` if this marker defines the function body to have a plural
+  /// result, that is, either an [Iterable] or a [Stream].
+  final bool isYielding;
+
+  final AsyncModifier asyncParserState;
+
+  const AsyncMarker._(this.asyncParserState,
+      {this.isAsync: false, this.isYielding: false});
+
+  String toString() {
+    return '${isAsync ? 'async' : 'sync'}${isYielding ? '*' : ''}';
+  }
+
+  /// Canonical list of marker values.
+  ///
+  /// Added to make [AsyncMarker] enum-like.
+  static const List<AsyncMarker> values = const <AsyncMarker>[
+    SYNC,
+    SYNC_STAR,
+    ASYNC,
+    ASYNC_STAR
+  ];
+
+  /// Index to this marker within [values].
+  ///
+  /// Added to make [AsyncMarker] enum-like.
+  int get index => values.indexOf(this);
 }
 
 /// Stripped down super interface for constructor like entities.
 ///
 /// Currently only [ConstructorElement] but later also kernel based Dart
 /// constructors and/or Dart-in-JS constructor-like properties.
 // TODO(johnniwinther): Remove factory constructors from the set of
 // constructors.
 abstract class ConstructorEntity extends FunctionEntity {
   /// Whether this is a generative constructor, possibly redirecting.
@@ skipping 49 matching lines @@
   int get optionalParameters =>
       positionalParameters - requiredParameters + namedParameters.length;
 
   /// Returns the [CallStructure] corresponding to a call site passing all
   /// parameters both required and optional.
   CallStructure get callStructure {
     return new CallStructure(
         positionalParameters + namedParameters.length, namedParameters);
   }
 }