Chain</a></emu-nt>.</li><li>Let <var>newBaseReference</var> be ? ChainEvaluation of <var>optionalChain</var> with arguments <var>baseValue</var> and <var>baseReference</var>.</li><li>Let <var>newBaseValue</var> be ?&nbsp;<emu-xref aoid="GetValue" id="_ref_18"><a href="https://tc39.es/ecma262/#sec-getvalue">GetValue</a></emu-xref>(<var>newBaseReference</var>).</li><li>Let <var>startExpression</var> be the first <emu-nt><a href="https://tc39.es/ecma262/#prod-AssignmentExpression">AssignmentExpression</a></emu