Can there be special treatment for foreach ( var item in xx ?? [ ])

[zms9110750]

  public class TreeNode<T>(T value) : IList<TreeNode<T>>
  {
      // ...

  }

now:

foreach (var node in TreeNode ?? [] )  //CS0019

foreach (var node in TreeNode ?? (TreeNode<int>) [] ) // CS9214

foreach (var node in TreeNode as IEnumerable<TreeNode<int>> ?? []) // Work
``

[huoyaoyuan]

It's effectively a combination of #2473 and #9562, and the former was rejected because of breaking change.

With linq, .AsEnumerable() ?? [] is a less-verbose solution.

[jnm2]

This may be a use case for foreach?. That's come up in threads a while back, when we often suggested ?? [] instead.

[GabeSchaffer]

The foreach? statement (null conditional foreach) was considered in an LDM back in the C# 8 timeframe, but set aside:
https://github.com/dotnet/csharplang/blob/main/meetings/2018/LDM-2018-07-16.md#null-conditional-await-foreach