Fix for a couple of cascade tests.

pkg/analyzer/test/generated/parser_fasta_test.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/token.dart' as analyzer;
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/generated/parser.dart' as analyzer;
 import 'package:analyzer/src/generated/utilities_dart.dart';
@@ skipping 358 matching lines @@
   }
 
   @override
   @failingTest
   void test_parseCascadeSection_ii_typeArgumentComments() {
     super.test_parseCascadeSection_ii_typeArgumentComments();
   }
 
   @override
   @failingTest
-  void test_parseCascadeSection_p_assign_withCascade() {
-    super.test_parseCascadeSection_p_assign_withCascade();
-  }
-
-  @override
-  @failingTest
   void test_parseCascadeSection_p_assign_withCascade_typeArgumentComments() {
     super.test_parseCascadeSection_p_assign_withCascade_typeArgumentComments();
   }
 
   @override
   @failingTest
-  void test_parseCascadeSection_p_assign_withCascade_typeArguments() {
-    super.test_parseCascadeSection_p_assign_withCascade_typeArguments();
-  }
-
-  @override
-  @failingTest
   void test_parseCascadeSection_pa_typeArgumentComments() {
     super.test_parseCascadeSection_pa_typeArgumentComments();
   }
 
   @override
   @failingTest
   void test_parseCascadeSection_paa_typeArgumentComments() {
     super.test_parseCascadeSection_paa_typeArgumentComments();
   }
 
@@ skipping 354 matching lines @@
   }
 
   @override
   Expression parseBitwiseXorExpression(String code) {
     return _parseExpression(code);
   }
 
   @override
   Expression parseCascadeSection(String code) {
     var cascadeExpression = _parseExpression('null$code') as CascadeExpression;
-    return cascadeExpression.cascadeSections.single;
+    return cascadeExpression.cascadeSections.first;
   }
 
   @override
   CompilationUnit parseCompilationUnit(String source,
       [List<ErrorCode> errorCodes = const <ErrorCode>[]]) {
     return _runParser(source, (parser) => parser.parseUnit, errorCodes)
         as CompilationUnit;
   }
 
   @override
@@ skipping 730 matching lines @@
   void test_parseTypeAlias_genericFunction_typeParameters_voidReturnType() {
     super.test_parseTypeAlias_genericFunction_typeParameters_voidReturnType();
   }
 
   @override
   @failingTest
   void test_parseTypeAlias_genericFunction_voidReturnType() {
     super.test_parseTypeAlias_genericFunction_voidReturnType();
   }
 }