VirtualFiles for scala runner

[som-snytt]

Today I benefited from the warning

12 |object Test:
   |       ^
   |object Test differs only in case from class test. Such classes will overwrite one another on case-insensitive filesystems.
1 warning found
Exception in thread "main" java.lang.NoSuchMethodError: 'scala.languageFeature$postfixOps Test$.c()'

which for some reason includes WSL? No wait, that can't be right. Oh, I had a local Test.class file and the scala runner's classpath is wrong.

Be that as it may, it would be nice if we could say, scala -d virtual myapp.scala or some magic URI to use in-memory outputs only, like REPL.