sdk/lib/compiler/implementation/tree_validator.dart

// Copyright (c) 2011, 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 TreeValidatorTask extends CompilerTask {
  TreeValidatorTask(Compiler compiler) : super(compiler);

  void validate(Node tree) {
    assert(check(tree));
  }

  bool check(Node tree) {
    List<InvalidNodeError> errors = [];
    void report(node, message) {
      final error = new InvalidNodeError(node, message);
      errors.add(error);
      compiler.reportWarning(node, message);
    };
    final validator = new ValidatorVisitor(report);
    tree.accept(new TraversingVisitor(validator));

    return errors.isEmpty();
  }
}

class ValidatorVisitor extends AbstractVisitor {
  final Function reportInvalidNode;

  ValidatorVisitor(Function this.reportInvalidNode);

  expect(Node node, bool test, [message]) {
    if (!test) reportInvalidNode(node, message);
  }

  visitNode(Node node) {}

  visitSendSet(SendSet node) {
    final selector = node.selector;
    final name = node.assignmentOperator.source.stringValue;
    final arguments = node.arguments;

    expect(node, arguments !== null);
    expect(node, selector is Identifier, 'selector is not assignable');
    if (name === '++' || name === '--') {
      expect(node, node.assignmentOperator is Operator);
      if (node.isIndex) {
        expect(node.arguments.tail.head, node.arguments.tail.isEmpty());
      } else {
        expect(node.arguments.head, node.arguments.isEmpty());
      }
    } else {
      expect(node, !node.arguments.isEmpty());
    }
  }
}

class InvalidNodeError {
  final Node node;
  final String message;
  InvalidNodeError(this.node, [this.message]);

  toString() {
    String nodeString = node.toDebugString();
    String result = 'invalid node: $nodeString';
    if (message !== null) result = '$result ($message)';
    return result;
  }
}