Sluicing has traditionally been analyzed as an operation involving wh-movement and deletion (Merchant 2001). French is a language that has both fronted and wh-in situ strategies; on the surface, however, it seems that French sluices do not involve (overt) movement, in spite of this being an available option. For nearly all wh-words, the in situ and moved forms are the same; the exception is que/quoi ‘what’— que is found in fronted wh-questions alone, while quoi is found in situ. In sluicing, only quoi surfaces, suggesting that French may be a challenge for the movement-and-deletion approach (Dagnac 2019).
By formalizing an analysis within a late insertion approach to the syntax-morphology interface, I argue that not only do sluices in French involve full structure, but that they involve movement as well. I assume that the wh-word is initially represented in the syntactic derivation as an abstract feature bundle. The morphological form is determined in the mapping of syntax to morphology by locality-dependent Vocabulary Insertion (VI) rules that are sensitive to C. These rules apply only after ellipsis occurs. Following Thoms (2010), I argue that C is targeted in sluicing, and as a result destroys the context that would trigger que. This analysis is able to capture sluicing in French, while explaining the behavior of quoi more generally.