From the docs: "Sscanln, Fscanln and Sscanln stop scanning at a newline and require
that the items be followed by one."

If one of the items implements Scanner, the scanning will only stop scanning at a newline
if the Scan method decides to.

either ScanState.ReadRune should return EOF when it gets to a newline in this case, or
it should be possible to find out from ScanState whether we're inside one of the *ln
functions.

i can see arguments both ways.