Using Should().Throw() with Func<T> fails after upgrading to version 5.5.0

Description

After upgrading FluentAssertions from version 5.4.2 to 5.5.0, usage of Should().Throw<T> with async method does not yield expected behavior. The following code example functions as expected with version 5.4.2.

Complete minimal example reproducing the issue

public class FluentAssertionsExceptionTests
{
    [Fact]
    public void Test1()
    {
        Func<Task<int>> func1 = () => TestAsync(false);
        func1.Should().NotThrow<Exception>();

        // Does not assert thrown exception
        Func<Task<int>> func2 = () => TestAsync(true);
        func2.Should().Throw<Exception>();
    }

    private async Task<int> TestAsync(bool throwException)
    {
        if (throwException)
        {
            throw new Exception("Error");
        }

        return await Task.FromResult(123);
    }
}

Expected behavior:

The assertion for the thrown exception passes.

Actual behavior:

The assertion for the thrown exception does not pass. The assertion does not detect the thrown exception.

Xunit.Sdk.XunitException
  HResult=0x80131500
  Message=Expected System.Exception, but no exception was thrown.
  Source=FluentAssertions
  StackTrace:
   at FluentAssertions.Execution.XUnit2TestFramework.Throw(String message)
   at FluentAssertions.Execution.AssertionScope.FailWith(Func`1 failReasonFunc)
   at FluentAssertions.Specialized.FunctionAssertions`1.Throw[TException](Exception exception, String because, Object[] becauseArgs)
   at FluentAssertions.Specialized.FunctionAssertions`1.Throw[TException](String because, Object[] becauseArgs)

Versions

Visual Studio 2017, .NET Core 2.1, XUnit 2.4.1, FluentAssertions 5.5.0

Additional Information

Removal of the ‘TResult’ argument from the Func<Task<T>> yields expected behavior and the assertion functions as expected with version 5.5.0.

Func<Task> func3 = () => TestAsync(true);
func3.Should().Throw<Exception>();

[jnyrup]

It seems doable with the following new overload of Should()

public static AsyncFunctionAssertions Should<T>(this Func<Task<T>> action)
{
    return new AsyncFunctionAssertions(action, extractor);
}

[krajek]

I will take a look in the evening.