Example usage of NullabilityInfoContext fails on preview.7

[SimonCropp]

• 6.0.100-preview.7.21379.14
• Current Window10
• VS2019 Preview

here dotnet/core#6444 (comment) the following (slightly modified) example is used

class Target
{
    public (string?, object) TupleField;
}

[Fact]
public void Test()
{
    var type = typeof(Target);
    var tupleField = type.GetField("TupleField");

    var context = new NullabilityInfoContext();

    var tupleInfo = context.Create(tupleField);

    Assert.Equal(NullabilityState.NotNull, tupleInfo.ReadState);
    Assert.Equal(NullabilityState.Nullable, tupleInfo.GenericTypeArguments[0].ReadState);
    Assert.Equal(NullabilityState.NotNull, tupleInfo.GenericTypeArguments[1].ReadState);
}

it fails since tupleInfo.GenericTypeArguments is empty.

I am not sure if this is a bug, or if the API has evolved beyond that example.

Paging @buyaa-n since you posted that usage example

[buyaa-n]

@SimonCropp thank you for reporting, you are right, the example is supposed to have a Tuple, not ValueTuple, i have updated the example with:
public Tuple<string?, object> TupleField;

For some reason i thought no need to check generics for value types, but now I think it should work for ValueTuple, i will fix that, CC @jeffhandley @terrajobst

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[SimonCropp]

@buyaa-n BTW i discovered this when i was building https://github.com/SimonCropp/NullabilityInfo which exposes the new api to older net frameworks via a code only package. if u have time i would appreciate any feedback on the approach

[SimonCropp]

thanks @buyaa-n