cmd/compile: invalid recursive type

[QuantumGhost]

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

go version go1.11 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.11/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.11/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/02/nfvdwz45077g85khfsv07khm0000gn/T/go-build787448559=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

https://play.golang.org/p/SMcx3vUC83W
Compile this code with Go 1.11 and Go 1.10.3 respectively.

What did you expect to see?

Code compiles without any error with both Go 1.11 and Go 1.10.3.

What did you see instead?

Go 1.11 failed to compile this code with the following error:
On my machine:

❯ go build recur.go
# command-line-arguments
./recur.go:10:6: invalid recursive type Executor
./recur.go:16:29: cannot use callback (type func(*Executor) error) as type Executor in field value
./recur.go:21:19: cannot call non-function e.callback (type Executor)

Go 1.10.3 succeeded without any issue.

[agnivade]

Likely a duplicate of #27232.

/cc @josharian @mdempsky

[josharian]

Likely a duplicate of #27232.

Indeed.

This and #27232 are more in the domain of @mdempsky or @griesemer than me. (And I also don't have much time at the moment, and these seem like important fixes that could use a prompt backport.)

[FiloSottile]

(If this turns out NOT to be a duplicate of #27232, please open a separate backport issue.)

[griesemer]

Simpler reproducer, with irrelevant details stripped:

package p

type F = func(E) // compiles if not type alias or moved below E struct

type E struct {
	f F
}

var _ = E{func(E) {}}

This looks very much like a duplicate of #27232, though with different details. Leaving open until we know more.

[griesemer]

Simpler reproducer:

package p

type P = *S

type S struct {
	p P
}

The problem appears to be an incorrectly built type data structure for S after type-checking, such that the type of S.p is S rather than *S. The consequence is the error when calling checkwidth.

[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