POC moq ReadOnlySpan Issue

This is my repo with some code that reproduces the issue on my system.

Usage

Run the unit test project

From your console:

PS C:\source\poc\moq-ros-issue\src> dotnet test

Run sample web api

This shows that the sample code works.

From your console

PS C:\source\poc\moq-ros-issue\src> dotnet run --project .\WebSample\WebSample.csproj

Once started, in a browser navigate to https://localhost:5001/api/values.

Results of running test project

PS C:\source\poc\moq-ros-issue\src> dotnet test
Skipping running test for project C:\source\poc\moq-ros-issue\src\WebSample\WebSample.csproj. To run tests with dotnet test add "<IsTestProject>true<IsTestProject>" property to project file.
Build started, please wait...
Build completed.

Test run for C:\source\poc\moq-ros-issue\src\Test\bin\Debug\netcoreapp2.2\Test.dll(.NETCoreApp,Version=v2.2)
Microsoft (R) Test Execution Command Line Tool Version 15.9.0
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
[xUnit.net 00:00:01.09]     Test.ValuesControllerTest.Fails_At_Runtime [FAIL]
Failed   Test.ValuesControllerTest.Fails_At_Runtime
Error Message:
 System.NotSupportedException : Cannot create boxed ByRef-like values.
Stack Trace:
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean wrapExceptions, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean wrapExceptions, Boolean skipCheckThis, Boolean fillCache)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic, Boolean wrapExceptions)
   at Moq.LookupOrFallbackDefaultValueProvider.GetDefaultValue(Type type, Mock mock) in C:\projects\moq4\src\Moq\LookupOrFallbackDefaultValueProvider.cs:line 127
   at Moq.Mock.GetDefaultValue(MethodInfo method, DefaultValueProvider useAlternateProvider) in C:\projects\moq4\src\Moq\Mock.cs:line 909
   at Moq.Return.Handle(Invocation invocation, Mock mock) in C:\projects\moq4\src\Moq\Interception\InterceptionAspects.cs:line 343
   at Moq.Mock.Moq.IInterceptor.Intercept(Invocation invocation) in C:\projects\moq4\src\Moq\Interception\Mock.cs:line 20
   at Castle.DynamicProxy.AbstractInvocation.Proceed()
   at Castle.Proxies.IFooServiceProxy.GetSomeData()
   at WebSample.Controllers.ValuesController.Get() in C:\source\poc\moq-ros-issue\src\WebSample\Controllers\ValuesController.cs:line 25
   at Test.ValuesControllerTest.Fails_At_Runtime() in C:\source\poc\moq-ros-issue\src\Test\ValuesControllerTest.cs:line 17

Total tests: 1. Passed: 0. Failed: 1. Skipped: 0.
Test Run Failed.
Test execution time: 2.1398 Seconds

dotnet --info