(Beta2)
When I press Ctrl-Space here:
module X = {
@react.component
let make = (~a: string, ~b: int) => React.string(a ++ string_of_int(b))
}
<X a="hello" b=42
I get this:

i.e. a and b are in the list even though they already have values assigned.
(In TypeScript, only props that were not assigned any values yet are shown in the list.)