Update the plugin API

pkg/analyzer_plugin/lib/utilities/fixes/fixes.dart

 // Copyright (c) 2017, 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/dart/analysis/results.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/file_system/file_system.dart';
-import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart';
 import 'package:analyzer_plugin/protocol/protocol_generated.dart';
 import 'package:analyzer_plugin/src/utilities/fixes/fixes.dart';
 import 'package:analyzer_plugin/utilities/generator.dart';
 
 /**
+ * The information about a requested set of fixes when computing fixes in a
+ * `.dart` file.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+abstract class DartFixesRequest implements FixesRequest {
+  /**
+   * The analysis result for the file in which the fixes are being requested.
+   */
+  ResolveResult get result;
+}
+
+/**
  * An object that [FixContributor]s use to record fixes.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 abstract class FixCollector {
   /**
    * Record a new [change] (fix) associated with the given [error].
    */
   void addFix(AnalysisError error, PrioritizedSourceChange change);
 }
 
 /**
  * An object used to produce fixes.
  *
  * Clients may implement this class when implementing plugins.
  */
 abstract class FixContributor {
   /**
    * Contribute fixes for the location in the file specified by the given
    * [request] into the given [collector].
    */
-  void computeFixes(FixesRequest request, FixCollector collector);
+  void computeFixes(covariant FixesRequest request, FixCollector collector);
 }
 
 /**
  * The information about a requested set of fixes.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 abstract class FixesRequest {
   /**
    * The analysis error to be fixed, or `null` if the error has not been
    * determined.
    */
-  AnalysisError get error;
+  List<AnalysisError> get errorsToFix;
 
   /**
    * Return the offset within the source for which fixes are being requested.
    */
   int get offset;
 
   /**
    * Return the resource provider associated with this request.
    */
   ResourceProvider get resourceProvider;
-
-  /**
-   * The analysis result for the file in which the fixes are being requested.
-   */
-  ResolveResult get result;
 }
 
 /**
  * A generator that will generate an 'edit.getFixes' response.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 class FixGenerator {
   /**
    * The contributors to be used to generate the fixes.
    */
   final List<FixContributor> contributors;
 
   /**
    * Initialize a newly created fix generator to use the given [contributors].
    */
   FixGenerator(this.contributors);
 
   /**
    * Create an 'edit.getFixes' response for the location in the file specified
    * by the given [request]. If any of the contributors throws an exception,
    * also create a non-fatal 'plugin.error' notification.
    */
   GeneratorResult generateFixesResponse(FixesRequest request) {
     List<Notification> notifications = <Notification>[];
     FixCollectorImpl collector = new FixCollectorImpl();
-    Iterable<AnalysisError> errors = _getErrors(request);
-    FixesRequestImpl requestImpl = request;
     for (FixContributor contributor in contributors) {
       try {
-        for (AnalysisError error in errors) {
-          requestImpl.error = error;
-          contributor.computeFixes(request, collector);
-        }
+        contributor.computeFixes(request, collector);
       } catch (exception, stackTrace) {
         notifications.add(new PluginErrorParams(
                 false, exception.toString(), stackTrace.toString())
             .toNotification());
-      } finally {
-        requestImpl.error = null;
       }
     }
     EditGetFixesResult result = new EditGetFixesResult(collector.fixes);
     return new GeneratorResult(result, notifications);
   }
-
-  Iterable<AnalysisError> _getErrors(FixesRequest request) {
-    int offset = request.offset;
-    LineInfo lineInfo = request.result.lineInfo;
-    int offsetLine = lineInfo.getLocation(offset).lineNumber;
-    return request.result.errors.where((AnalysisError error) {
-      int errorLine = lineInfo.getLocation(error.offset).lineNumber;
-      return errorLine == offsetLine;
-    });
-  }
 }