src/Composer/DependencyResolver/RuleWatchNode.php
public function watch2OnHighest(Decisions $decisions)
    {
        $literals = $this->rule->getLiterals();

        // if there are only 2 elements, both are being watched anyway
        if (count($literals) < 3) {
            return;
        }

        $watchLevel = 0;

        foreach ($literals as $literal) {
            $level = $decisions->decisionLevel($literal);

            if ($level > $watchLevel) {
                $this->watch2 = $literal;
                $watchLevel = $level;
            }
        }
    }
public function watch2OnHighest(Decisions $decisions)
    {
        $literals = $this->rule->getLiterals();

        // if there are only 2 elements, both are being watched anyway
        if (count($literals) < 3) {
            return;
        }

        $watchLevel = 0;

        foreach ($literals as $literal) {
            $level = $decisions->decisionLevel($literal);

            if ($level > $watchLevel) {
                $this->watch2 = $literal;
                $watchLevel = $level;
            }
        }
    }
Places the second watch on the rule's literal, decided at the highest level

Useful for learned rules where the literal for the highest rule is most
likely to quickly lead to further decisions.

@param Decisions $decisions The decisions made so far by the solver