Support accessing the parameter element when there is no name

pkg/analyzer/lib/src/dart/element/builder.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.
 
 library analyzer.src.dart.element.builder;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/exception/exception.dart';
+import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 
 /**
@@ skipping 1372 matching lines @@
     parameter.isExplicitlyCovariant = node.parameter.covariantKeyword != null;
     parameter.isFinal = node.isFinal;
     parameter.parameterKind = node.kind;
     // visible range
     _setParameterVisibleRange(node, parameter);
     if (normalParameter is SimpleFormalParameter &&
         normalParameter.type == null) {
       parameter.hasImplicitType = true;
     }
     _currentHolder.addParameter(parameter);
+    if (normalParameter is SimpleFormalParameterImpl) {
+      normalParameter.element = parameter;
+    }
     parameterName.staticElement = parameter;
     normalParameter.accept(this);
     return null;
   }
 
   @override
   Object visitFunctionTypedFormalParameter(FunctionTypedFormalParameter node) {
     if (node.parent is! DefaultFormalParameter) {
       SimpleIdentifier parameterName = node.identifier;
       ParameterElementImpl parameter =
@@ skipping 16 matching lines @@
     ParameterElementImpl element = node.element;
     element.metadata = _createElementAnnotations(node.metadata);
     element.parameters = holder.parameters;
     element.typeParameters = holder.typeParameters;
     holder.validate();
     return null;
   }
 
   @override
   Object visitSimpleFormalParameter(SimpleFormalParameter node) {
+    ParameterElementImpl parameter;
     if (node.parent is! DefaultFormalParameter) {
       SimpleIdentifier parameterName = node.identifier;
-      ParameterElementImpl parameter =
-          new ParameterElementImpl.forNode(parameterName);
+      parameter = new ParameterElementImpl.forNode(parameterName);
       _setCodeRange(parameter, node);
       parameter.isConst = node.isConst;
       parameter.isExplicitlyCovariant = node.covariantKeyword != null;
       parameter.isFinal = node.isFinal;
       parameter.parameterKind = node.kind;
       _setParameterVisibleRange(node, parameter);
       if (node.type == null) {
         parameter.hasImplicitType = true;
       }
       _currentHolder.addParameter(parameter);
-      parameterName.staticElement = parameter;
+      (node as SimpleFormalParameterImpl).element = parameter;
+      parameterName?.staticElement = parameter;
     }
     super.visitSimpleFormalParameter(node);
-    (node.element as ElementImpl).metadata =
-        _createElementAnnotations(node.metadata);
+    parameter ??= node.element;
+    parameter?.metadata = _createElementAnnotations(node.metadata);
     return null;
   }
 
   @override
   Object visitTypeParameter(TypeParameter node) {
     SimpleIdentifier parameterName = node.name;
     TypeParameterElementImpl typeParameter =
         new TypeParameterElementImpl.forNode(parameterName);
     _setCodeRange(typeParameter, node);
     typeParameter.metadata = _createElementAnnotations(node.metadata);
@@ skipping 153 matching lines @@
     return null;
   }
 
   /**
    * Return the lexical identifiers associated with the given [identifiers].
    */
   static List<String> _getIdentifiers(NodeList<SimpleIdentifier> identifiers) {
     return identifiers.map((identifier) => identifier.name).toList();
   }
 }