public override SucoExpression Optimize(SucoEnvironment env, int?[] givens)
{
var valueExpr = ValueExpression.Optimize(env, givens);
var innerExpr = InnerExpression.Optimize(env.DeclareVariable(VariableName, valueExpr is SucoConstant c ? c.Value : null), givens);
return(innerExpr is SucoConstant ? innerExpr : new SucoLetExpression(StartIndex, EndIndex, VariableName, valueExpr, innerExpr, Type));
}