Go: cmd/compile: failure on a function type alias

[falconandy]

What version of Go are you using (go version)?

go version go1.11 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

Without empty values:
GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/falconandy/go"
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build437619988=/tmp/go-build -gno-record-gcc-switches

What did you do?

https://play.golang.org/p/ydDs-6YdK64

What did you expect to see?

Compiled successfully

What did you see instead?

cannot use parser literal (type *parser) as type Parser in return argument:
*parser does not implement Parser (wrong type for AddOperator method)
have AddOperator(string, func(Parser))
want AddOperator(string, Parser)

[cznic]

I'm probably missing something but the code linked at the Playground compiles and executes just fine. Can you please provide a reproducer that actually fails with the error in the OP?

[falconandy]

Playground works on Go 1.10.3 - so it's fine there

[cznic]

Thanks, I can reproduce the fail now. Seems like a genuine regression to me.

[agnivade]

@josharian @mdempsky

Seems like a backport candidate.

[FiloSottile]

@gopherbot please file this for backport against 1.11. This is a regression.

@griesemer please make a cherry-pick CL once your change is merged in master.

[gopherbot]

Backport issue(s) opened: #27383 (for 1.11).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://golang.org/wiki/MinorReleases.

[FiloSottile]

@agnivade feel free to make a backport issue as soon as you want something considered for backport. Anyone can and should do that, and the decision on backporting can be made on that issue.

[agnivade]

Roger.

[griesemer]

Simpler reproducer, with irrelevant details stripped:

package p

type F = func(T) // compiles if not type alias or moved below T interface

type T interface {
    m(F)
}

type t struct{}

func (t) m(F) {}

var _ T = &t{}

[griesemer]

Probably a duplicate of #25838. Leaving open for now.

[gopherbot]

Change https://golang.org/cl/147286 mentions this issue: cmd/compile: reintroduce work-around for cyclic alias declarations

[gopherbot]

Change https://golang.org/cl/151339 mentions this issue: [release-branch.go1.11] cmd/compile: reintroduce work-around for cyclic alias declarations