Improve type information and minor clean up

pkg/analyzer/lib/source/config.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.
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/source/analysis_options_provider.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/task/model.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:package_config/packages.dart';
 import 'package:yaml/src/yaml_node.dart';
 import 'package:yaml/yaml.dart';
 
 /// The descriptor used to associate analysis configuration with analysis
 /// contexts in configuration data.
 final ResultDescriptor<AnalysisConfiguration> ANALYSIS_CONFIGURATION =
     new ResultDescriptorImpl('analysis.config', null);
 
 /// Return configuration associated with this [context], or `null` if there is
 /// none.
 AnalysisConfiguration getConfiguration(AnalysisContext context) =>
-    context.getConfigurationData(ANALYSIS_CONFIGURATION)
-    as AnalysisConfiguration;
+    context.getConfigurationData(ANALYSIS_CONFIGURATION);
 
 /// Associate this [config] with the given [context].
 void setConfiguration(AnalysisContext context, AnalysisConfiguration config) {
   context.setConfigurationData(ANALYSIS_CONFIGURATION, config);
 }
 
 /// Analysis configuration.
 abstract class AnalysisConfiguration {
   final AnalysisOptionsProvider optionsProvider = new AnalysisOptionsProvider();
   final Packages packages;
   final ResourceProvider resourceProvider;
   AnalysisConfiguration(this.resourceProvider, this.packages);
 
   factory AnalysisConfiguration.fromPubspec(
           File pubspec, ResourceProvider resourceProvider, Packages packages) =>
       new PubspecConfiguration(pubspec, resourceProvider, packages);
 
   /// Get a map of options defined by this configuration (or `null` if none
   /// are specified).
   Map get options;
 }
 
 /// Describes an analysis configuration.
 class AnalysisConfigurationDescriptor {
   /// The name of the package hosting the configuration.
   String package;
+
   /// The name of the configuration "pragma".
   String pragma;
 
   AnalysisConfigurationDescriptor.fromAnalyzerOptions(Map analyzerOptions) {
     Object config = analyzerOptions['configuration'];
     if (config is String) {
       List<String> items = config.split('/');
       if (items.length == 2) {
         package = items[0].trim();
         pragma = items[1].trim();
@@ skipping 38 matching lines @@
             }
           }
         }
       } catch (_) {
         // Skip exceptional configurations.
       }
     }
     return null;
   }
 }