Fix many bugs with closure conversion in checked mode.

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 17 matching lines @@
   void insertExtendContext(VectorSet extender);
 
   void _createDeclaration() {
     assert(contextDeclaration == null && vectorCreation == null);
 
     // Context size is set to 2 initially, because the 0-th element of it holds
     // the vector of type arguments that the VM creates, and the 1-st element
     // works as a link to the parent context.
     vectorCreation = new VectorCreation(2);
     contextDeclaration = new VariableDeclaration.forValue(vectorCreation,
-        type: new VectorType());
+        type: const DynamicType());
     contextDeclaration.name = "#context";
   }
 }
 
 /// Adds a local variable for the context and adds update [Statement]s to the
 /// current block.
 class BlockRewriter extends AstRewriter {
   Block _currentBlock;
   int _insertionIndex;
 
@@ skipping 57 matching lines @@
   }
 
   @override
   void insertExtendContext(VectorSet extender) {
     var init = new LocalInitializer(
         new VariableDeclaration(null, initializer: extender));
     init.parent = parentConstructor;
     prefix.add(init);
   }
 }