[Bug go/71396] New: "use of undefined type" error in gccgo-6 when go (1.6.1) is perfectly happy

["mvo at debian dot org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71396

            Bug ID: 71396
           Summary: "use of undefined type" error in gccgo-6 when go
                    (1.6.1) is perfectly happy
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: go
          Assignee: ian at airs dot com
          Reporter: mvo at debian dot org
                CC: cmang at google dot com
  Target Milestone: ---

Created attachment 38633
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38633&action=edit
Minimal testcase

We had a build failure in our go code with gccgo-6 (from Ubuntu 16.04: $
gccgo-6 --version
gccgo-6 (Ubuntu 6.0.1-0ubuntu1) 6.0.0 20160414 (experimental) [trunk revision
234994], same error with gccgo-5 fwiw):

"""
ok      github.com/snapcore/snapd/arch  0.159s
# github.com/snapcore/snapd/snap_test
src/github.com/snapcore/snapd/snap/info_test.go:60:3: error: use of undefined
type âRevisionâ
   Revision:          snap.R(1),
   ^
"""
(https://launchpadlibrarian.net/262885164/buildlog_ubuntu-yakkety-powerpc.snapd_2.0.6+16.10.2_BUILDING.txt.gz)

I tracked this down and condensed it into some minimal example go code
(attached). The issue is triggered by the "revision_test.go" import of ".". If
that is removed the tests work fine again.

With the attached testcase I get the following:
"""
$ go test && go-6 test
1
{{7}}
PASS
ok      _/tmp/2 0.001s
# _/tmp/2_test
./foo_test.go:11:3: error: use of undefined type âRevisionâ
   Revision: foo.R(1),
   ^
FAIL    _/tmp/2 [build failed]
"""
I.e. go test is happy, gccgo-6 is unhappy (with a error message that confused
me quite a bit :)

I hope this is useful for you. It's fine if the answer to this bugreport is:
"don't do this if it fails". However given that I already tracked it down I
felt I might as well share it with you.

Cheers,
 Michael