Start working on unparse validation.

lib/compiler/implementation/unparse_validator.dart

Index: lib/compiler/implementation/unparse_validator.dart
diff --git a/lib/compiler/implementation/unparse_validator.dart b/lib/compiler/implementation/unparse_validator.dart
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+++ b/lib/compiler/implementation/unparse_validator.dart
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+// 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.
+
+/**
+ * Checks result's of [Node] unparse.
+ */
+class UnparseValidator extends CompilerTask {
+  final bool validateUnparse;
+
+  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);
+    String unparsed = originalNode.unparse(false);
+
+    Token newTokens = new StringScanner(unparsed).tokenize();
+
+    // Find the getOrSet token.
+    // TODO(ahe): This is to frigging complicated. Simplify it.
+    Parser parser = new Parser(new Listener());
+    Token getOrSet =
+        parser.findGetOrSet(parser.parseModifiers(newTokens));
+
+    // TODO(ahe): This is also too frigging complicated.
+    Script originalScript = element.getCompilationUnit().script;
+    SourceFile synthesizedSourceFile =
+        new SourceFile(originalScript.name, unparsed);
+    Script synthesizedScript =
+        new Script(originalScript.uri, synthesizedSourceFile);
+    LibraryElement lib = new LibraryElement(synthesizedScript);
+    NodeListener listener = new NodeListener(compiler, lib);
+    parser = new Parser(listener);
+    // TODO(antonm): better error reporting.
+    compiler.withCurrentElement(lib, () {
+      parser.parseFunction(newTokens, getOrSet);
+    });
+    FunctionExpression newNode = listener.popNode();
+    // TODO(antonm): add Node comparison.
+  }
+}