Compile and run Hello World!

pkg/compiler/lib/src/kernel/kernel_backend_strategy.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 dart2js.kernel.backend_strategy;
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../backend_strategy.dart';
 import '../closure.dart';
@@ skipping 256 matching lines @@
   }
 
   @override
   void leaveInlinedMember(MemberEntity member) {
     assert(member == currentMember);
     _members.removeLast();
   }
 
   @override
   JumpTarget getJumpTarget(ir.TreeNode node, {bool isContinueTarget: false}) {
-    throw new UnimplementedError('KernelToLocalsMapImpl.getJumpTarget');
+    // TODO(johnniwinther): Support jump targets.
+    return null;

[Emily Fortuna, 2017/06/15 17:54:34]

is this really better than throwing? I mean, it gets hello world compiling, but
it's hiding issues.

[Siggi Cherem (dart-lang), 2017/06/15 18:28:55]

one option here: throw in checked mode only?

[Johnni Winther, 2017/06/16 09:25:31]

This is the price for the machete approach. We need to clean up the leaves
afterwards. In this case: returning `null` means [node] has no jumps to it,
which is true for loops without continue.

We run unittests in checked mode, so no. 

[Siggi Cherem (dart-lang), 2017/06/16 16:35:24]

How about:

if (const bool.fromEnvironment("MACHETE_CLEANUP")) throw "support jump targets";

[Johnni Winther, 2017/06/19 10:57:38]

I'll consider it.

   }
 
   @override
   Local getLocal(ir.VariableDeclaration node) {
     return _map.putIfAbsent(node, () {
       return new KLocal(node.name, currentMember);
     });
   }
 
   @override
@@ skipping 95 matching lines @@
   Iterable<ClassEntity> sortClasses(Iterable<ClassEntity> classes) {
     return classes.toList()
       ..sort((ClassEntity a, ClassEntity b) {
         int r = _compareLibraries(a.library, b.library);
         if (r != 0) return r;
         return _compareNodes(
             a, elementMap.getClassNode(a), b, elementMap.getClassNode(b));
       });
   }
 }