Deprecate object $ to avoid unsoundess #1395
Description
The Scala spec states that identifiers that contain the $ characters are reserved for compiler-generated names. Any other use has undefined behavior.
One of these (object $) caused a bug in scala/scala3#19702. We are trying to add an ad-hoc patch to support these broken classes from Ammonite. But this patch cannot be guaranteed to work forever and there is no guarantee that these definitions do not introduce more issues (that may not be by the compiler).
The following names can cause undefined behavior: object $, package $file, package $exec, package $ivy, package $url, package $stub, package $cp, package $plugin, package $repo. These are defined in https://github.com/com-lihaoyi/Ammonite/blob/main/amm/interp/api/src/main/scala/ammonite/Stubs.scala. There might be more problematic names.
The only possible solution is to deprecate these objects and migrate to some sound naming scheme.