anchor.diff:    @override
     visitBreakStatement(BreakStatement node) {
       var label = node.label;
  -    return new JS.Break(label != null ? label.name : null);
  +    return new JS.Break(label?.name);
     }
   
     @override
     visitContinueStatement(ContinueStatement node) {
       var label = node.label;
  -    return new JS.Continue(label != null ? label.name : null);
  +    return new JS.Continue(label?.name);
     }
   
     @override
  
positive.code:     var program = <JS.Statement>[
        js.statement("dart_library.library(#, #, #, #, #)", [
          js.string(jsPath, "'"),
          jsDefaultValue != null ? jsDefaultValue : new JS.LiteralNull(),
          js.commentExpression(
              "Imports", new JS.ArrayInitializer(imports, multiline: true)),
          js.commentExpression("Lazy imports",
  
negative.code:     var value = _visit(node.initializer);
      // explicitly initialize to null, to avoid getting `undefined`.
      // TODO(jmesserly): do this only for vars that aren't definitely assigned.
      return value ?? new JS.LiteralNull();
    }
  
    void _flushLazyFields(List<JS.Statement> body) {
  