Enumerable.Empty<T> in .NET Core 3.0 cannot be cast to IList<T> #27552
Description
Yes, casting is bad...so we probably shouldn't do this, but is it reasonable to expect this to keep working?
using System;
using System.Collections.Generic;
using System.Linq;
namespace cast_to_list
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine($"There are {GetBugs().Count} bugs in casting Enumerable.Empty<T> to IList<T>");
}
private static IList<int> GetBugs()
{
+ return (IList<int>)Enumerable.Empty<int>();
}
}
}
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFrameworks>netcoreapp2.1;netcoreapp3.0</TargetFrameworks>
</PropertyGroup>
</Project>
The cast works in .NET Core 2.1, but not 3.0. In 3.0, it fails with:
Unhandled Exception: System.InvalidCastException: Unable to cast object of type 'System.Linq.EmptyPartition`1[System.Int32]' to type 'System.Collections.Generic.IList`1[System.Int32]'.
I'm using .NET Core 2.1.5 and 3.0.0-preview1-27003-04.
