Don't type promote local functions.

pkg/front_end/lib/src/fasta/builder/ast_factory.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:front_end/src/fasta/scanner.dart' show Token;
 import 'package:front_end/src/fasta/type_inference/type_promotion.dart';
 import 'package:kernel/ast.dart';
 
 /// An abstract class containing factory methods that create AST objects.
 ///
@@ skipping 171 matching lines @@
   /// kernel, which desugars each variable declaration to its own statement.
   ///
   /// If the variable declaration did not have an explicitly declared type,
   /// [type] should be `null`.
   VariableDeclaration variableDeclaration(
       String name, Token token, int functionNestingLevel,
       {DartType type,
       Expression initializer,
       Token equalsToken,
       bool isFinal: false,
-      bool isConst: false});
+      bool isConst: false,
+      bool isLocalFunction: false});
 
   /// Creates a read of a local variable.
   VariableGet variableGet(VariableDeclaration variable,
       TypePromotionFact<V> fact, TypePromotionScope scope, Token token);
 
   /// Creates a write of a local variable.
   VariableSet variableSet(VariableDeclaration variable, Expression value);
 }