Yes, I'd absolutely agree that pure functions are declarative, so "functional" is a subset of "declarative".
But it's a strict subset: config files are declarative without being functional. Raw data is declarative without being functional. One could argue that imperative functions are declarative too: "This C code is the declaration of what steps to execute in what order". So the definition of declarative can be a little fuzzy around the edges, but pure functions are most certainly declarative.
Anyway, QML is most certainly declarative, however it's still not functional because there's no functions.
But it's a strict subset: config files are declarative without being functional. Raw data is declarative without being functional. One could argue that imperative functions are declarative too: "This C code is the declaration of what steps to execute in what order". So the definition of declarative can be a little fuzzy around the edges, but pure functions are most certainly declarative.
Anyway, QML is most certainly declarative, however it's still not functional because there's no functions.