GitLab

It was mishandling conjunctions containing negations.

Change-Id: Ife571b28416870ba2ceadbdac5ecb4670432bba1
Reviewed-on: https://go-review.googlesource.com/9151

Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>