ValueTuple: what is wrong with creation of octuple?

Question

ValueTuple as a new feature in C# 7.0 is having public method Create which helps to create ValueTuples (from singleton to octuple or more) on the other hand we can also use new to achieve the same results. I noticed these behave differently. I am trying to research is below implementation wrong or this is something as per design:

Method CreateOctuple() is working as expected:

private static ValueTuple<int, int, int, int, int, int, int, ValueTuple<int>> CreateOctuple()
{
     return new ValueTuple<int, int, int, int, int, int, int, ValueTuple<int>>(1, 2, 3, 4, 5, 6, 7, new ValueTuple<int>(8)); ;
}

Now, I tried to achieve same output using Create() method, unfortunately, it is complaining about the return type:

private static ValueTuple<int, int, int, int, int, int, int, ValueTuple<int>> OctupleUsingCreate()
{
    return ValueTuple.Create(1, 2, 3, 4, 5, 6, 7, ValueTuple.Create(8));
}

What is wrong here?

P.S. All packages are up-to-date and I am using Visual Studio 2017 -latest release.

As suggested by Svick

static ValueTuple<int, int, int, int, int, int, int, ValueTuple<int>> OctupleUsingCreate()
{
  return ValueTuple.Create(1, 2, 3, 4, 5, 6, 7, 8);
}

This prompts same compiler exception:

score 5 · Accepted Answer · answered May 21 '17 at 13:46

5

The issue is that ValueTuple.Create already takes care of calling ValueTuple.Create on the 8th element. So while the correct type for 8-tuple is ValueTuple<int, int, int, int, int, int, int, ValueTuple<int>>, you're creating ValueTuple<int, int, int, int, int, int, int, ValueTuple<ValueTuple<int>>>. The fix is just to remove the second call to ValueTuple.Create:

static ValueTuple<int, int, int, int, int, int, int, ValueTuple<int>> OctupleUsingCreate()
{
    return ValueTuple.Create(1, 2, 3, 4, 5, 6, 7, 8);
}

Or you could just use the tuple syntax, but I'm assuming you have a reason to avoid it:

static (int, int, int, int, int, int, int, int) OctupleUsingCreate()
{
    return (1, 2, 3, 4, 5, 6, 7, 8);
}

answered May 21 '17 at 13:46

svick

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I've already tried that. But it was not working. I updated the question with snapshot and the code as sugegsted. – Gaurav Arora May 21 '17 at 14:00
@GauravAroraa That's just a ReSharper bug. The code actually compiles and works fine. – svick May 21 '17 at 14:07
2

@GauravAroraa I have just [reported it](https://youtrack.jetbrains.com/issue/RSRP-464845). – svick May 21 '17 at 14:17
Code is compiled - on another system, where Resharper is not installed. – Gaurav Arora May 21 '17 at 14:28
@GauravAroraa Even if you have ReSharper installed, you can compile it. The red squiglies will still be there, but the build will succeed without errors. – svick May 21 '17 at 14:58
its compiled but tests are failing. I know it looks weird but its happening. Thanks for raising ticket with Resharper team. – Gaurav Arora May 23 '17 at 08:38

score 0 · Answer 2 · edited May 23 '17 at 12:26

0

You need to update this package: Microsoft.Net.Compilers to 2.0 (you need to show pre-release). It would fix the error, check this here

edited May 23 '17 at 12:26

Community

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answered May 21 '17 at 07:44

developer_hatch

15,898
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Thanks for prompt response. All Nuget Packages are uptodate I have updated the question with screenshot. – Gaurav Arora May 21 '17 at 08:24

score 0 · Answer 3 · answered May 28 '17 at 21:12

Note: This is not a problem with the ValueTuple library or the C# compiler. No error on TryRoslyn with:

using System;
public class C 
{
    private static ValueTuple<int, int, int, int, int, int, int, ValueTuple<int>> OctupleUsingCreate()
    {
        return ValueTuple.Create(1, 2, 3, 4, 5, 6, 7, 8);
    }
}

ValueTuple: what is wrong with creation of octuple?

3 Answers3