Update AssistProcessor to use ChangeBuilder

pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_core.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 'dart:async';
 
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
 
@@ skipping 211 matching lines @@
     EditBuilderImpl builder = createEditBuilder(range.offset, range.length);
     fileEdit.add(builder.sourceEdit);
   }
 
   @override
   void addInsertion(int offset, void buildEdit(EditBuilder builder)) {
     EditBuilderImpl builder = createEditBuilder(offset, 0);
     try {
       buildEdit(builder);
     } finally {
-      fileEdit.add(builder.sourceEdit);
-      _captureSelection(builder);
+      SourceEdit edit = builder.sourceEdit;
+      fileEdit.add(edit);
+      _captureSelection(builder, edit);
     }
   }
 
   @override
   void addLinkedPosition(SourceRange range, String groupName) {
     LinkedEditGroup group = changeBuilder.getLinkedEditGroup(groupName);
     Position position = new Position(
         fileEdit.file, range.offset + _deltaToOffset(range.offset));
     group.addPosition(position, range.length);
   }
 
   @override
   void addReplacement(SourceRange range, void buildEdit(EditBuilder builder)) {
     EditBuilderImpl builder = createEditBuilder(range.offset, range.length);
     try {
       buildEdit(builder);
     } finally {
-      fileEdit.add(builder.sourceEdit);
-      _captureSelection(builder);
+      SourceEdit edit = builder.sourceEdit;
+      fileEdit.add(edit);
+      _captureSelection(builder, edit);
     }
   }
 
   @override
   void addSimpleInsertion(int offset, String text) {
     EditBuilderImpl builder = createEditBuilder(offset, 0);
     try {
       builder.write(text);
     } finally {
-      fileEdit.add(builder.sourceEdit);
-      _captureSelection(builder);
+      SourceEdit edit = builder.sourceEdit;
+      fileEdit.add(edit);
+      _captureSelection(builder, edit);
     }
   }
 
   @override
   void addSimpleReplacement(SourceRange range, String text) {
     EditBuilderImpl builder = createEditBuilder(range.offset, range.length);
     try {
       builder.write(text);
     } finally {
-      fileEdit.add(builder.sourceEdit);
-      _captureSelection(builder);
+      SourceEdit edit = builder.sourceEdit;
+      fileEdit.add(edit);
+      _captureSelection(builder, edit);
     }
   }
 
   EditBuilderImpl createEditBuilder(int offset, int length) {
     return new EditBuilderImpl(this, offset, length);
   }
 
   /**
    * Finalize the source file edit that is being built.
    */
   void finalize() {
     // Nothing to do.
   }
 
   /**
    * Capture the selection offset if one was set.
    */
-  void _captureSelection(EditBuilderImpl builder) {
+  void _captureSelection(EditBuilderImpl builder, SourceEdit edit) {
     int offset = builder._selectionOffset;
     if (offset >= 0) {
       Position position =
-          new Position(fileEdit.file, offset + _deltaToOffset(offset));
+          new Position(fileEdit.file, offset + _deltaToEdit(edit));
       changeBuilder.setSelection(position);
     }
   }
 
   /**
    * Return the current delta caused by edits that will be applied before the
+   * [targetEdit]. In other words, if all of the edits that occur before the
+   * target edit were to be applied, then the text at the offset of the target
+   * edit before the applied edits will be at `offset + _deltaToOffset(offset)`
+   * after the edits.
+   */
+  int _deltaToEdit(SourceEdit targetEdit) {
+    int delta = 0;
+    for (SourceEdit edit in fileEdit.edits) {
+      if (edit.offset < targetEdit.offset) {
+        delta += edit.replacement.length - edit.length;
+      }
+    }
+    return delta;
+  }
+
+  /**
+   * Return the current delta caused by edits that will be applied before the
    * given [offset]. In other words, if all of the edits that have so far been
    * added were to be applied, then the text at the given `offset` before the
-   * edits will be at `offset + deltaToOffset(offset)` after the edits.
+   * applied edits will be at `offset + _deltaToOffset(offset)` after the edits.
    */
-  int _deltaToOffset(int targetOffset) {
-    int offset = 0;
-    for (var edit in fileEdit.edits) {
-      if (edit.offset <= targetOffset) {
-        offset += edit.replacement.length - edit.length;
+  int _deltaToOffset(int offset) {
+    int delta = 0;
+    for (SourceEdit edit in fileEdit.edits) {
+      if (edit.offset <= offset) {
+        delta += edit.replacement.length - edit.length;
       }
     }
-    return offset;
+    return delta;
   }
 }
 
 /**
  * A builder used to build a [LinkedEdit] region within an edit.
  */
 class LinkedEditBuilderImpl implements LinkedEditBuilder {
   final EditBuilderImpl editBuilder;
 
   final List<LinkedEditSuggestion> suggestions = <LinkedEditSuggestion>[];
@@ skipping 13 matching lines @@
   @override
   void write(String string) {
     editBuilder.write(string);
   }
 
   @override
   void writeln([String string]) {
     editBuilder.writeln(string);
   }
 }