The comment for fmt.Fscan says:

It returns the number of items successfully scanned. If that is less than the number of
arguments, err will report why.


But fmt.Fscanf only says:

It returns the number of items successfully parsed.


From reading the source, it seems that the formatted variants are also intended to
return a non-nil error for short scans:
http://play.golang.org/p/aS0XEsQLWp

If so, the documentation should be made consistent to reflect this.