Missing position in kind mismatch (during effect desugaring)

[rajdakin]

The following code:

sig f : Comp({}, Bool)
fun f() { () }

fails with the error:

:0: Kind mismatch: Type argument 1 for type constructor Comp has kind Row, but an argument of kind Type was expected. 
In:
<dummy>

which does not contain any location information. This is due to these lines: https://github.com/links-lang/links/blob/5156ea3ee216c537f4bb0afdd8ae61aa2a30f308/core/desugarEffects.ml#L881

https://github.com/links-lang/links/blob/5156ea3ee216c537f4bb0afdd8ae61aa2a30f308/core/desugarEffects.ml#L905-L908

Note that the dummy position is also present elsewhere in this file; I did not try to find an example which makes use of that fact.