VSTHRD110 mis-fires on null coalescing operator

[AArnott]

Bug description

When an async method's result is returned with ?? operator, VSTHRD110 claims the result isn't returned or awaited.

Repro steps

        internal Task<T> GetClientAsync<T>(CancellationToken cancellationToken) where T : VssHttpClientBase
        {
            return _vssConnection?.GetClientAsync<T>(cancellationToken) ?? Task.FromResult<T>(null);
        }

Expected behavior

No warning.

Actual behavior

A warning.

[drewnoakes]

Duplicate of #880?

[AArnott]

The two issues are regarding distinct analyzers. I wouldn't know till fixing it whether there is common code behind each analyzer such that fixing one will implicitly fix the other.

[peterdrier]

private Task ShakeTreeAsync() => Tree?.ShakeAsync() ?? Task.CompletedTask;

A simple example causing a VSTHRD110 warning where it shouldn't.