> In the -show-basis output of MLton, what is the exact meaning of a signature > expression of the form > sigexp where datatype tyvarseq longtycon = ty > (which I don't see in the definition and am assuming is some kind of informal > extension just for this output)? That's a bug in the basis pretty printer. I've committed a fix. You can just replace "datatype" with "type", which is all the fix does.