This adds the `!!` syntax for the compiler to add a null check on that parameter. See dotnet/csharplang#2145 and the [feature spec](https://github.com/dotnet/csharplang/blob/main/proposals/param-nullchecking.md)
This adds the
!!syntax for the compiler to add a null check on that parameter. See dotnet/csharplang#2145 and the feature spec