Handle null literal in compile_from_dill

pkg/compiler/lib/src/ssa/builder_kernel.dart

 // Copyright (c) 2016, 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:kernel/ast.dart' as ir;
 
 import '../closure.dart';
 import '../common.dart';
 import '../common/codegen.dart' show CodegenRegistry;
 import '../common/names.dart';
@@ skipping 813 matching lines @@
 
   @override
   void visitReturnStatement(ir.ReturnStatement returnStatement) {
     HInstruction value;
     if (returnStatement.expression == null) {
       value = graph.addConstantNull(closedWorld);
     } else {
       assert(_targetFunction != null && _targetFunction is ir.FunctionNode);
       returnStatement.expression.accept(this);
       value = pop();
-      DartType returnType = astAdapter.getFunctionReturnType(_targetFunction);
+      DartType returnType = _elementMap.getFunctionType(_targetFunction);
       if (_targetFunction.asyncMarker == ir.AsyncMarker.Async) {
         if (options.enableTypeAssertions &&
             !isValidAsyncReturnType(returnType)) {
           generateTypeError(
               returnStatement,
               "Async function returned a Future,"
               " was declared to return a ${returnType}.");
           pop();
           return;
         }
@@ skipping 2580 matching lines @@
     enterBlock.setBlockFlow(
         new HTryBlockInformation(
             kernelBuilder.wrapStatementGraph(bodyGraph),
             exception,
             kernelBuilder.wrapStatementGraph(catchGraph),
             kernelBuilder.wrapStatementGraph(finallyGraph)),
         exitBlock);
     kernelBuilder.inTryStatement = previouslyInTryStatement;
   }
 }