TSpawnResult = enum
  srVoid, srFlowVar, srByVar

proc spawnResult(t: PType; inParallel: bool): TSpawnResult {...}{.
    raises: [Exception], tags: [RootEffect].}

proc wrapProcForSpawn(g: ModuleGraph; owner: PSym; spawnExpr: PNode;
                      retType: PType; barrier, dest: PNode = nil): PNode {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}