foo1.cs

        var orExpression = condition as IConditionalOrExpression;
        if (orExpression != null)
        {
          return ToSimpleConditions(leftOperand) && ToSimpleConditions(rightOperand);
        }

        var andExpression = condition as IConditionalAndExpression;
        if (andExpression == null || myCSharpLanguageLevel < CSharpLanguageLevel.CSharp60)
          return false;
        
        var polyadicExpression = Polyadic<ICSharpExpression>.Build(condition, CSharpTokenType.ANDAND);
        var firstExpression = polyadicExpression.Expressions.FirstOrDefault().GetOperandThroughParenthesisStrict();
        if (firstExpression == null
            || firstExpression is IConditionalAndExpression
            || firstExpression is IConditionalOrExpression)
          return false;

        var subexpression = polyadicExpression.Subexpression(1, polyadicExpression.Expressions.Count - 1);
        return ToSimpleConditions(firstExpression, subexpression);

foo2.cs

        switch (condition)
        {
          case IConditionalOrExpression orExpression:
            return ToSimpleConditions(leftOperand) && ToSimpleConditions(rightOperand);

          case IConditionalAndExpression andExpression when myCSharpLanguageLevel => CSharpLanguageLevel.CSharp60:
            var polyadicExpression = Polyadic<ICSharpExpression>.Build(condition, CSharpTokenType.ANDAND);
            var firstExpression = polyadicExpression.Expressions.FirstOrDefault().GetOperandThroughParenthesisStrict();
            if (firstExpression == null
              || firstExpression is IConditionalAndExpression
              || firstExpression is IConditionalOrExpression)
              return false;

            var subexpression = polyadicExpression.Subexpression(1, polyadicExpression.Expressions.Count - 1);
            return ToSimpleConditions(firstExpression, subexpression);

          default:
            return false;
        }

foo3.cs

        switch (condition)
        {
          case IConditionalOrExpression orExpression:
            return ToSimpleConditions(leftOperand) && ToSimpleConditions(rightOperand);

          case IConditionalAndExpression andExpression when myCSharpLanguageLevel => CSharpLanguageLevel.CSharp60:
            var polyadicExpression = Polyadic<ICSharpExpression>.Build(condition, CSharpTokenType.ANDAND);
            switch (polyadicExpression.Expressions.FirstOrDefault().GetOperandThroughParenthesisStrict())
            {
              case null:
              case IConditionalAndExpression _:
              case IConditionalOrExpression _:
                return false;

              case var firstExpression:
                var subexpression = polyadicExpression.Subexpression(1, polyadicExpression.Expressions.Count - 1);
                return ToSimpleConditions(firstExpression, subexpression);
            }

          default:
            return false;
        }