var MESSAGE =
  'Using the delete operator on a property will cause the shape of ' +
  'the object to change. This will lead to JS engine to de-optimize ' +
  'read and writes to this object.';

// For now this rule is very pessimistic to limit false positives. It only
// covers case of form: delete this.<identifier>;
module.exports = function rule(context) {
  return {
    UnaryExpression: function(node) {
      if (node.operator !== 'delete') {
        return;
      }
      var deleteArg = node.argument;
      if (deleteArg.type !== 'MemberExpression') {
        return;
      }
      var obj = deleteArg.object;
      var property = deleteArg.property;
      if (obj.type !== 'ThisExpression') {
        return;
      }
      if (property.type !== 'Identifier') {
        return;
      }
      context.report(node, MESSAGE);
    },
  };
};