src/Composer/DependencyResolver/RuleSetGenerator.php
protected function createRemoveRule(PackageInterface $package, $reason, $job)
    {
        return new GenericRule(array(-$package->id), $reason, $job['packageName'], $job);
    }
protected function createRemoveRule(PackageInterface $package, $reason, $job)
    {
        return new GenericRule(array(-$package->id), $reason, $job['packageName'], $job);
    }
Creates a rule to remove a package

The rule for a package A is (-A).

@param  PackageInterface $package The package to be removed
@param  int              $reason  A RULE_* constant describing the
reason for generating this rule
@param  array            $job     The job this rule was created from
@return Rule             The generated rule