A name and a path: document.qu is qu hanging off document, doc is doc off nothing.
base: string
The expression whose properties could finish the token, or '' for a bare name.
Only ever a dotted path of plain identifiers. Anything else — foo().bar, list[0]., a
string in mid-flight — is not a base and this reports no completion at all, because the base
has to be EVALUATED to find out what is on it, and a keystroke is no reason to run somebody's
function call.
token: string
The partial identifier under the cursor, empty directly after a dot.