They do not convert a plural into a singular.
(Introduced recently, in CL 77050.)

Change-Id: I3b6c4d03b1866d4133e90b8ab05e8d4bfbd55125
Reviewed-on: https://go-review.googlesource.com/82078
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>