The "-mİş" forms in Turkish are traditionally given as examples of evidentiality:
geliyor (he's coming; implies direct knowledge, generally visual) geliyormuş (he's coming; implies indirect knowledge, generally acquired from someone else)
The second form can also be the indirect version of
geliyordu (he was coming) and may also encode other types of (somehow related) aspectual/modal/evidential information (for example when the speaker has just noticed that "he's coming").
But I've never seen a thorough analysis of "-Dİr" forms like
geliyordur. These forms, among other things, may be used to encode that it's a guess made by the speaker. They can be used with (the Turkish equivalents of) "I'm sure that", "I think that", "probably", "maybe" etc.
It does not necessarily encode inferential evidence which can also be done with the indirect form above or periphrastically (
geliyor olmalı, "he must be coming"). In fact, it can be used in case of total lack of evidence to express pure guesswork. Does lack of evidence and pure guesswork count as evidentiality? Or is there another term for it?
Note: Here, my analysis of "-Dİr" forms are not very relevant. There are too many complications in their usage. My question is simply: "Can a form that expresses lack of evidence be classified as an evidential?"