코틀린 반환값 미사용 검사

<div class="r2 returncheck" data-step="0"><div class="r2-head">RETURN VALUE CHECK<span class="r2-live"></span></div><div class="r2-stage"><div class="r2-code-line">calculate()</div><div class="r2-return-flow"><span>42</span><span>→</span><span class="r2-consumer">consumer</span></div><div class="r2-warning">unused result</div></div><div class="r2-foot"><span class="r2-caption"></span><span class="r2-progress"></span></div></div>

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