I realized this simplification was possible when writing the vet loop
(just above the code being modified here) but never circled back
to make the compiler loop match.

Change-Id: Ic2277d2a4b6d94ea4897cc3615fc1a29f2fb243c
Reviewed-on: https://go-review.googlesource.com/78395
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>