More generic function type cases working

pkg/analyzer/lib/src/summary/summarize_ast.dart

 // Copyright (c) 2016, 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 serialization.summarize_ast;
 
 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/type.dart' show DartType;
@@ skipping 1324 matching lines @@
   void visitGenericTypeAlias(GenericTypeAlias node) {
     int oldScopesLength = scopes.length;
     _TypeParameterScope typeParameterScope = new _TypeParameterScope();
     scopes.add(typeParameterScope);
     UnlinkedTypedefBuilder b = new UnlinkedTypedefBuilder();
     b.style = TypedefStyle.genericFunctionType;
     b.name = node.name.name;
     b.nameOffset = node.name.offset;
     b.typeParameters =
         serializeTypeParameters(node.typeParameters, typeParameterScope);
-    EntityRefBuilder serializedType =
-        serializeGenericFunctionType(node.functionType);
+    GenericFunctionType functionType = node.functionType;
+    EntityRefBuilder serializedType = functionType == null
+        ? null
+        : serializeGenericFunctionType(functionType);
     if (serializedType != null) {
       b.returnType = serializedType;
     }
     b.documentationComment = serializeDocumentation(node.documentationComment);
     b.annotations = serializeAnnotations(node.metadata);
     b.codeRange = serializeCodeRange(node);
     typedefs.add(b);
     scopes.removeLast();
     assert(scopes.length == oldScopesLength);
   }
@@ skipping 124 matching lines @@
 /**
  * A [_TypeParameterScope] is a [_Scope] which defines [_ScopedTypeParameter]s.
  */
 class _TypeParameterScope extends _Scope {
   /**
    * Get the number of [_ScopedTypeParameter]s defined in this
    * [_TypeParameterScope].
    */
   int get length => _definedNames.length;
 }