public override Formula Visit(ReturnFormula formula)
 {
     IncreaseIfNecessary(formula.Body, _ => _.TypeDeclaration, increased => formula.Body = increased);
     return base.Visit(formula);
 }
 public Formula Visit(ReturnFormula formula)
 {
     return formula;
 }
 public virtual Formula Visit(ReturnFormula formula)
 {
     Visit((Formula)formula);
     if (formula.Body != null) formula.Body.Accept(this);
     return visitor.Visit(formula);
 }