Validate that all instructions dominate their inputs. And fix a bug where that did not happen.

lib/compiler/implementation/unparse_validator.dart

 // Copyright (c) 2012, 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.
 
 class ValidatorListener implements DiagnosticListener {
   final SourceFile sourceFile;
 
   ValidatorListener(this.sourceFile);
 
   void cancel([String reason, node, token, instruction, element]) {
     assert(token !== null);
     SourceSpan.withOffsets(token, token, (beginOffset, endOffset) {
         String errorMessage =
             sourceFile.getLocationMessage(reason, beginOffset, endOffset, true);
         print(errorMessage);
     });
     throw new CompilerCancelledException(reason);
   }
 
   void log(message) {}
 }
 
 /**
  * Checks result's of [Node] unparse.
  */
 class UnparseValidator extends CompilerTask {
   final bool validateUnparse;
 
+  String get name() => "Unparse validator";
+
   UnparseValidator(Compiler compiler, this.validateUnparse) : super(compiler);
 
   void check(Element element) {
     if (!validateUnparse) return;
 
     // TODO(antonm): consider supporting other kinds of elements.
     if (element is! PartialFunctionElement) return;
 
     PartialFunctionElement originalFunction = element;
     FunctionExpression originalNode = originalFunction.parseNode(compiler);
@@ skipping 18 matching lines @@
         new Script(originalScript.uri, synthesizedSourceFile);
     LibraryElement lib = new LibraryElement(synthesizedScript);
     NodeListener listener =
         new NodeListener(new ValidatorListener(synthesizedSourceFile), lib);
     parser = new Parser(listener);
     parser.parseFunction(newTokens, getOrSet);
     FunctionExpression newNode = listener.popNode();
     // TODO(antonm): add Node comparison.
   }
 }