Fix invalid initializing formal by adding a field

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

 // Copyright (c) 2014, 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 'dart:collection';
 import 'dart:core';
 
 import 'package:analysis_server/plugin/edit/fix/fix_core.dart';
 import 'package:analysis_server/plugin/edit/fix/fix_dart.dart';
@@ skipping 378 matching lines @@
     }
     if (errorCode == StaticTypeWarningCode.UNDEFINED_SETTER) {
       await _addFix_undefinedClassAccessor_useSimilar();
       await _addFix_createField();
     }
     if (errorCode == CompileTimeErrorCode.UNDEFINED_NAMED_PARAMETER ||
         errorCode == StaticWarningCode.UNDEFINED_NAMED_PARAMETER) {
       await _addFix_convertFlutterChild();
       await _addFix_convertFlutterChildren();
     }
+    if (errorCode ==
+        CompileTimeErrorCode.INITIALIZING_FORMAL_FOR_NON_EXISTENT_FIELD) {
+      await _addFix_createField_initializingFormal();
+    }
     // lints
     if (errorCode is LintCode) {
       if (errorCode.name == LintNames.annotate_overrides) {
         await _addFix_addOverrideAnnotation();
       }
       if (errorCode.name == LintNames.avoid_annotating_with_dynamic) {
         await _addFix_removeTypeName();
       }
       if (errorCode.name == LintNames.avoid_init_to_null) {
         await _addFix_removeInitializer();
@@ skipping 765 matching lines @@
     utils.targetClassElement = targetClassElement;
     // prepare target ClassDeclaration
     AstNode targetTypeNode = getParsedClassElementNode(targetClassElement);
     if (targetTypeNode is! ClassDeclaration) {
       return;
     }
     ClassDeclaration targetClassNode = targetTypeNode;
     // prepare location
     ClassMemberLocation targetLocation =
         utils.prepareNewFieldLocation(targetClassNode);
-    // build method source
+    // build field source
     Source targetSource = targetClassElement.source;
     String targetFile = targetSource.fullName;
     DartChangeBuilder changeBuilder = new DartChangeBuilder(driver);
     await changeBuilder.addFileEdit(targetFile, targetSource.modificationStamp,
         (DartFileEditBuilder builder) {
       Expression fieldTypeNode = climbPropertyAccess(nameNode);
       DartType fieldType = _inferUndefinedExpressionType(fieldTypeNode);
       builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
         builder.write(targetLocation.prefix);
         builder.writeFieldDeclaration(name,
             isStatic: staticModifier,
             nameGroupName: 'NAME',
             type: fieldType,
             typeGroupName: 'TYPE');
         builder.write(targetLocation.suffix);
       });
     });
     _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_FIELD, args: [name]);
   }
 
+  Future<Null> _addFix_createField_initializingFormal() async {
+    //
+    // Ensure that we are in an initializing formal parameter.
+    //
+    FieldFormalParameter parameter =
+        node.getAncestor((node) => node is FieldFormalParameter);
+    if (parameter == null) {
+      return;
+    }
+    ClassDeclaration targetClassNode =
+        parameter.getAncestor((node) => node is ClassDeclaration);
+    if (targetClassNode == null) {
+      return;
+    }
+    SimpleIdentifier nameNode = parameter.identifier;
+    String name = nameNode.name;
+    ClassMemberLocation targetLocation =
+        utils.prepareNewFieldLocation(targetClassNode);
+    //
+    // Add proposal.
+    //
+    DartChangeBuilder changeBuilder = new DartChangeBuilder(driver);
+    await changeBuilder.addFileEdit(file, fileStamp,
+        (DartFileEditBuilder builder) {
+      DartType fieldType = parameter.type?.type;
+      builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
+        builder.write(targetLocation.prefix);
+        builder.writeFieldDeclaration(name,
+            nameGroupName: 'NAME', type: fieldType, typeGroupName: 'TYPE');
+        builder.write(targetLocation.suffix);
+      });
+    });
+    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_FIELD, args: [name]);
+  }
+
   Future<Null> _addFix_createFunction_forFunctionType() async {
     if (node is SimpleIdentifier) {
       SimpleIdentifier nameNode = node as SimpleIdentifier;
       // prepare argument expression (to get parameter)
       ClassElement targetElement;
       Expression argument;
       {
         Expression target = getQualifiedPropertyTarget(node);
         if (target != null) {
           DartType targetType = target.bestType;
@@ skipping 1960 matching lines @@
       }
     }
   }
 
   void _updateList(Iterable<Element> elements) {
     for (Element element in elements) {
       _update(element);
     }
   }
 }