According to @StoneyB's Cannonical Post #2 . States cannot serve as the complement in Wh-cleft constructions. As an example there,
- What John did was have written three novels. – This is not idiomatic English
But what disturb my mind is, what if the state serve as the complement in this kind of sentence
All John did was have written three novels.
Is this sentence grammatical and idiomatic?