foo1.cs

[Pure]
private static bool IsFullyDiscardedDeconstructionExpression([NotNull] ITupleCreationExpression tupleCreationExpression)
{
  foreach (var tupleArgument in tupleCreationExpression.ArgumentsEnumerable)
  {
    if (tupleArgument.NameIdentifier != null) return false;
    if (tupleArgument.Colon != null) return false;

    var tupleArgumentValue = tupleArgument.Value;

    var referenceExpression = tupleArgumentValue as IReferenceExpression;
    if (referenceExpression != null)
    {
      if (referenceExpression.IsDiscardReferenceExpression()) continue;
      return false;
    }

    var innerDeconstruction = tupleArgumentValue as ITupleCreationExpression;
    if (innerDeconstruction != null)
    {
      if (IsFullyDiscardedDeconstructionExpression(innerDeconstruction)) continue;
      return false;
    }

    var declarationExpression = tupleArgumentValue as IDeclarationExpression;
    if (declarationExpression != null)
    {
      var designation = declarationExpression.Designation;
      if (designation is IDiscardDesignation) continue;

      var parenthesizedDesignation = designation as IParenthesizedVariableDesignation;
      if (parenthesizedDesignation != null && IsFullyDiscardedParenthsizedDesignation(parenthesizedDesignation)) continue;
      
      return false;
    }
    
    return false;
  }

  return true;
}

foo2.cs

[Pure]
private static bool IsFullyDiscardedDeconstructionExpression([NotNull] ITupleCreationExpression tupleCreationExpression)
{
  foreach (var tupleArgument in tupleCreationExpression.ArgumentsEnumerable)
  {
    if (tupleArgument.NameIdentifier != null) return false;
    if (tupleArgument.Colon != null) return false;

    switch (tupleArgument.Value)
    {
      case IReferenceExpression referenceExpression when referenceExpression.IsDiscardReferenceExpression():
      case ITupleCreationExpression innerDeconstruction when IsFullyDiscardedDeconstructionExpression(innerDeconstruction):
        continue;
      
      case IDeclarationExpression declarationExpression:
        switch (declarationExpression.Designation)
        {
          case IDiscardDesignation _:
          case IParenthesizedVariableDesignation parenthesizedDesignation
               when IsFullyDiscardedParenthsizedDesignation(parenthesizedDesignation):
            continue;
          default:
            return false;
        }
        
      default:
        return false;
    }
  }

  return true;
}