Fix closure conversion in field and local initializers.

pkg/kernel/lib/transformations/closure/rewriter.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.
 
 library kernel.transformations.closure.rewriter;
 
 import '../../ast.dart';
 import 'converter.dart' show ClosureConverter;
 
 /// Used by the [Context] to initialize and update the context variable
@@ skipping 82 matching lines @@
   InitializerRewriter(this.initializingExpression);
 
   @override
   BlockRewriter forNestedBlock(Block block) {
     return new BlockRewriter(block);
   }
 
   @override
   void insertContextDeclaration(Expression accessParent) {
     _createDeclaration();
+    var oldParent = initializingExpression.parent;
     Let binding = new Let(contextDeclaration, initializingExpression);
+    binding.parent = oldParent;
     setInitializerExpression(binding);
-    initializingExpression.parent = binding;
   }
 
   @override
   void insertExtendContext(VectorSet extender) {
     Let parent = initializingExpression.parent;
     Let binding = new Let(new VariableDeclaration(null, initializer: extender),
         initializingExpression);
     parent.body = binding;
     binding.parent = parent;
   }
 
   void setInitializerExpression(Expression expression);
 }
 
 class FieldInitializerRewriter extends InitializerRewriter {
   FieldInitializerRewriter(Expression initializingExpression)
       : super(initializingExpression) {
     assert(initializingExpression.parent is FieldInitializer);
   }
 
   void setInitializerExpression(Expression expression) {
-    assert(initializingExpression.parent is FieldInitializer);
-    FieldInitializer parent = initializingExpression.parent;
-    parent.value = expression;
-    expression.parent = parent;
+    expression.parent.value = expression;
   }
 }
 
 class LocalInitializerRewriter extends InitializerRewriter {
   LocalInitializerRewriter(Expression initializingExpression)
       : super(initializingExpression) {
-    assert(initializingExpression.parent is LocalInitializer);
+    // The initializer is up two levels because the variable declaration node is
+    // in between.
+    assert(initializingExpression.parent.parent is LocalInitializer);
   }
 
   void setInitializerExpression(Expression expression) {
-    assert(initializingExpression.parent is LocalInitializer);
-    LocalInitializer parent = initializingExpression.parent;
-    parent.variable.initializer = expression;
-    expression.parent = parent;
+    expression.parent.initializer = expression;
   }
 }