This routine lets us climb up the AST tree when we find
a contiguous sequence of nodes that satisfy our predicate.
This will be useful for making things like `a.b.<CURSOR>`
work. That is, we don't want the `ExprAttribute` closest
to a leaf. We also don't always want the `ExprAttribute`
closest to the root. Rather, (I think) we want the
`ExprAttribute` closest to the root that has an unbroken
chain to the `ExprAttribute` closest to the leaf.
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