Ast_helper.MsModule substitutions
Module substitutions
val mk : 
  ?loc:Astlib.Location.t ->
  ?attrs:Astlib.Ast_500.Parsetree.attribute list ->
  string Astlib.Location.loc ->
  Astlib.Longident.t Astlib.Location.loc ->
  Astlib.Ast_500.Parsetree.module_substitution