Flow analysis regression causing failure in runtime repo

[buyaa-n]

A bug fix made with Perform exceptions path analysis for all flow analyses introduced regression in flow analyses and causing failures in runtime repo.

This call site is reachable on: 'freebsd'. 'HttpConnectionPool.TrySendUsingHttp3Async(HttpRequestMessage, CancellationToken)' is only supported on: 'linux', 'macOS/OSX', 'windows'.

The HttpConnectionPool.TrySendUsingHttp3Async(HttpRequestMessage, CancellationToken) was guarded with IsHttp3Supported(), but that not working anymore. I was not able to repro with a simpler code, so pasted the runtime code below, removed parts that not affecting the code analysis (like code in catch blocks etc, the full code could be found here). The warning disappears if remove the finally or 2 of the 3 catch blocks.

    public async ValueTask<HttpResponseMessage> SendWithVersionDetectionAndRetryAsync(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
    {
        while (true)
        {
            HttpConnectionWaiter<Http2Connection?>? http2ConnectionWaiter = null;
            try
            {
                HttpResponseMessage? response = null;

                if (IsHttp3Supported() && // guard to enable trimming HTTP/3 support
                    _http3Enabled &&
                    (request.Version.Major >= 3 || (request.VersionPolicy == HttpVersionPolicy.RequestVersionOrHigher && IsSecure)) &&
                    !request.IsExtendedConnectRequest)
                {
                    if (_sslOptionsHttp3 == null)
                    {
                        // deferred creation. We use atomic exchange to be sure all threads point to single object to mimic ctor behavior.
                        SslClientAuthenticationOptions sslOptionsHttp3 = ConstructSslOptions(_poolManager, _sslOptionsHttp11!.TargetHost!);
                        sslOptionsHttp3.ApplicationProtocols = s_http3ApplicationProtocols;
                        Interlocked.CompareExchange(ref _sslOptionsHttp3, sslOptionsHttp3, null);
                    }

                    response = await TrySendUsingHttp3Async(request, cancellationToken).ConfigureAwait(false);
                }
                return response!;
            }
            catch (HttpRequestException e) when (e.AllowRetry == RequestRetryType.RetryOnConnectionFailure)
            {    }
            catch (HttpRequestException e) when (e.AllowRetry == RequestRetryType.RetryOnLowerHttpVersion)
            {     }
            catch (HttpRequestException e) when (e.AllowRetry == RequestRetryType.RetryOnStreamLimitReached)
            {    }
            finally
            {
                CancelIfNecessary(http2ConnectionWaiter, cancellationToken.IsCancellationRequested);
            }
        }
    }

Blocking dotnet/runtime#89630.
@mavasani please take a look.

[mavasani]

Thanks @buyaa-n looking.