Setting LangVersion to Latest Causes an Error

[JasonBock]

To reproduce this:

Create a new .NET Core console app with this in the .csproj file:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <LangVersion>latest</LangVersion>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.1</TargetFramework>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="BenchmarkDotNet" Version="0.12.1" />
  </ItemGroup>
</Project>

Set the Program.cs file to have the same code as shown in the "Getting Started" page: https://benchmarkdotnet.org/articles/guides/getting-started.html.

The key is the setting for <LangVersion>. If I set it to a specific value, like 8.0, the tests run as expected. If I set it to latest, I get this error:

 Standard error:
 C:\Users\JasonB\source\repos\ConsoleApp35\ConsoleApp35\bin\Release\netcoreapp3.1\0192f748-6e76-46a0-a2b2-8204fb24ddc7\BenchmarkDotNet.Autogenerated.csproj(20,18): error MSB4086: A numeric comparison was attempted on "$(LangVersion)" that evaluates to "latest" instead of a number, in condition "'$(LangVersion)' == '' Or '$(LangVersion)' < '7.3'".

latest and preview values are valid, so this should not cause a problem.

[adamsitnik]

Hello @JasonBock

It's a bug that I've introduced in 0.12.1 and it was fixed in #1420 which is going to be part of next release.

For now please set the <LangVersion> to a number or downgrade to 0.12.0.

Thanks,
Adam