This confused me, so I mention it in case it confuses anyone else.
If predicative adjectives have type S[adj]\NP (because they come after the noun), NPs have type NP and the predicative copula has type (S[dcl]/(S[adj]\NP))/NP, then how do we cope with sentences that only have one NP? Where I went astray was assuming that if you have a word of type X/Y, then there has to be a Y somewhere in that sentence.
Not true! Tha i brèagha “it’s fine” (talking about the weather) is a good and simple example.
In this case, tha is of type (X/Y)/Z, and just forward composes with Z to its right and then Y next to the right. It just so happens that Y is a non-atomic type.
Now I’ve understood this I can worry about more complicated things.