Get an id of a thread that doesn't prevent its garbage collection.

Eq instance for ThreadId is broken in GHC < 9, see https://gitlab.haskell.org/ghc/ghc/-/issues/16761 for more info.

The type constructor Any is type to which you can unsafely coerce any lifted type, and back. More concretely, for a lifted type t and value x :: t, -- unsafeCoerce (unsafeCoerce x :: Any) :: t is equivalent to x.