.NET 6 source generators and C# 9 syntax

Question

If source generator projects must target netstandard2.0 ( C# 7.3 ), how and why do the examples in the .NET 6 incremental generator documentation use C# 9 syntax like static anonymous functions?

From the doc, formatted for width:

IncrementalValuesProvider<AdditionalText> textFiles =
   context.AdditionalTextsProvider.Where(static file =>
      file.Path.EndsWith(".txt"));

Answer 1

Just change the C# version in the .csproj file to 9, as in <LangVersion>9.0</LangVersion>