ModuleFoo.
The module needs at least one signature item, otherwise a bug causes the compiler to drop the module comment (above). See https://caml.inria.fr/mantis/view.php?id=7701 .
      module 
       type 
       S
      
       = sig ... 
       end
      
     
    
      module 
       type S2
       = S
     
    
      module 
       M'
      
       : sig ... 
       end
      
     
    
      module 
       Mutually
      
       : sig ... 
       end
      
     
    
      module 
       Recursive
      
       : sig ... 
       end