Unused value assignment analysis doesn't handle ref locals

[sharwell]

Version Used: Visual Studio 2019 Preview 2

Found while working on coverlet-coverage/coverlet#309

Steps to Reproduce:

class Test
{
  int[] data = { 0 };

  void Method()
  {
    ref int target = ref data[0];
    target = 1;
  }
}

Expected Behavior:

IDE0059 is not reported for the assignment.

Actual Behavior:

IDE0059 is reported for the assignment.

[Tragetaschen]

Does this fix this as well?

private void test()
{
    ReadOnlySequence<byte> a = default;
    var count = 0;
    foreach (var _ in a) // IDE0059 smudge here on _
        ++count;
}

[mavasani]

Why is there a loop instead of count += a.Length? The diagnostic fires as it seems fishy for a foreach loop to never access the iteration variable.