Unable to use variables for PackageReferences after #2347

[cincuranet]

Now that package references are copied into generated csproj (#2347), using variables there results in failure, because the variable is not available there.

One way to make it fail:

• Create a console app with some benchmarks.
• Use this as a csproj (note the SomeVersion variable).

<Project Sdk="Microsoft.NET.Sdk">
	<PropertyGroup>
		<OutputType>Exe</OutputType>
		<TargetFramework>net7.0</TargetFramework>
		<ImplicitUsings>enable</ImplicitUsings>
		<Nullable>enable</Nullable>
	</PropertyGroup>
	<PropertyGroup>
		<SomeVersion>5.1.1</SomeVersion>
	</PropertyGroup>
	<ItemGroup>
		<PackageReference Include="BenchmarkDotNet" Version="0.13.7-nightly.20230713.34" />
		<PackageReference Include="Microsoft.Data.SqlClient" Version="$(SomeVersion)" />
	</ItemGroup>
</Project>

Program.cs for completenes.

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

namespace ConsoleApp1
{
    internal class Program
    {
        static void Main(string[] args)
        {
            BenchmarkRunner.Run<Demo>();
        }
    }

    [ShortRunJob]
    public class Demo
    {
        [Benchmark]
        public void FooBar()
        {
            Microsoft.Data.SqlClient.SqlConnection.ClearAllPools();
        }
    }
}

#2364 and #2295 seem to have same root cause as this.

[timcassell]

#2295 Is unrelated, as that was reported before we started copying PackageReferences. #2364 is indeed the same issue.