attribute attached to a boolean variable specifying what it means when the boolean is true

`type t````=`

`|` `OnMainThread` | (** the current procedure is running on the main thread *)
`|` `LockHeld` | (** a lock is currently held *)

``
`include InferStdlib.PrettyPrintable.PrintableOrderedType with type PrintableOrderedType.t := t`
`include InferStdlib.IStd.Caml.Set.OrderedType`
`type t`````
`val compare : t ‑> t ‑> int`
`val pp : InferStdlib.PrettyPrintable.F.formatter ‑> t ‑> unit`