A couple of tweaks.

pkg/analyzer/lib/src/kernel/resynthesize.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 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/standard_ast_factory.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/element.dart';
@@ skipping 291 matching lines @@
       List<TypeAnnotation> arguments = _buildTypeArguments(type.typeArguments);
       return AstTestFactory.typeName3(name, arguments)..type = type;
     }
     if (type is DynamicTypeImpl) {
       var name = AstTestFactory.identifier3('dynamic')
         ..staticElement = type.element
         ..staticType = type;
       return AstTestFactory.typeName3(name)..type = type;
     }
     // TODO(scheglov) Implement for other types.
-    throw new UnimplementedError('type: $type');
+    throw new UnimplementedError('type: (${type.runtimeType}) $type');
   }
 
   TypeArgumentList _buildTypeArgumentList(List<kernel.DartType> kernels) {
     int length = kernels.length;
     var types = new List<TypeAnnotation>(length);
     for (int i = 0; i < length; i++) {
       DartType type = _context.getType(null, kernels[i]);
       TypeAnnotation typeAnnotation = _buildType(type);
       types[i] = typeAnnotation;
     }
@@ skipping 395 matching lines @@
         for (var typeParameter in ctx.typeParameters) {
           if (typeParameter.name == name) {
             return typeParameter;
           }
         }
       }
     }
     throw new StateError('Not found $kernelTypeParameter in $context');
   }
 }