More generic function type cases working

pkg/analyzer/lib/src/dart/element/element.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.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 5154 matching lines @@
   @override
   int get nameOffset {
     int offset = super.nameOffset;
     if (offset == 0 && _unlinkedTypedef != null) {
       return _unlinkedTypedef.nameOffset;
     }
     return offset;
   }
 
   @override
-  List<ParameterElement> get parameters => function.parameters;
+  List<ParameterElement> get parameters =>
+      function?.parameters ?? const <ParameterElement>[];
 
   @override
-  DartType get returnType => function.returnType;
+  DartType get returnType => function?.returnType;
 
   @override
   FunctionType get type {
     if (_unlinkedTypedef != null && _type == null) {
       _type = new FunctionTypeImpl.forTypedef(this);
     }
     return _type;
   }
 
   void set type(FunctionType type) {
@@ skipping 31 matching lines @@
       buffer.write("<");
       for (int i = 0; i < typeParameterCount; i++) {
         if (i > 0) {
           buffer.write(", ");
         }
         (typeParameters[i] as TypeParameterElementImpl).appendTo(buffer);
       }
       buffer.write(">");
     }
     buffer.write(" = ");
-    (function as FunctionElementImpl).appendTo(buffer);
+    if (function != null) {
+      (function as ElementImpl).appendTo(buffer);
+    }
   }
 
   @override
   FunctionTypeAlias computeNode() =>
       getNodeMatching((node) => node is GenericTypeAlias);
 
   @override
   ElementImpl getChild(String identifier) {
     for (TypeParameterElement typeParameter in typeParameters) {
       TypeParameterElementImpl typeParameterImpl = typeParameter;
@@ skipping 3863 matching lines @@
 
   @override
   void visitElement(Element element) {
     int offset = element.nameOffset;
     if (offset != -1) {
       map[offset] = element;
     }
     super.visitElement(element);
   }
 }