cmd/compile: internal compiler error in Go 1.18 using type parameters

[danielgtaylor]

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

$ go version
go version go1.18 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/user/Library/Caches/go-build"
GOENV="/Users/user/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/user/go/pkg/mod"
GONOPROXY="github.com/redacted"
GONOSUMDB="github.com/redacted"
GOOS="darwin"
GOPATH="/Users/user/go"
GOPRIVATE="github.com/redacted"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.18"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/user/src/tmp/go.mod"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/rv/chjwd3812yzf6fm1j66m8g_40000gp/T/go-build2308498026=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I triggered an internal compiler error while playing around with Go 1.18 type parameters (generics). From https://go.dev/play/p/AlyOOLesUjM:

package main

import (
	"fmt"
	"net/http"
)

type None struct{}

type Response interface {
	send(ctx *struct{})
}

type HandlerFunc[Input any] func(Input) Response

func Operation[Input any](method, path string, h HandlerFunc[Input]) {
	var input Input
	response := h(input)
	fmt.Println(response)
}

func Get[Headers, Body any](path string, h HandlerFunc[struct {
	Headers Headers
	Body    Body
}]) {
	Operation(http.MethodGet, path, h)
}

func main() {
	Get("/", func(req struct {
		Headers struct {
			Authorization string
		}
		Body None
	}) Response {
		return nil
	})
}

What did you expect to see?

Successful compilation.

What did you see instead?

./prog.go:30:5: internal compiler error: assigning h (type HandlerFunc[struct { Headers struct { Authorization string }; Body "".None }]) to parameter h (type HandlerFunc[go.shape.struct { Headers struct { Authorization string }; Body struct {} }_0])

Please file a bug report including a short program that triggers the error.
https://go.dev/issue/new

Go build failed.

[ALTree]

Crashes on tip too. Thanks for reporting.

cc @mdempsky @findleyr

[findleyr]

Thanks for the report.

CC @randall77

[cuonglm]

It seems to me this is the reverse of #49309.

There, we don't inline a function that has no shape parameters, but is passed at least one shape arg. Here, we may not want to inline a function that has shape parameters, but is passed no shape arg.

cc @randall77 @danscales

[mdempsky]

Successfully builds and runs (prints <nil>\n as output) with GOEXPERIMENT=unified.

[gopherbot]

Change https://go.dev/cl/395854 mentions this issue: cmd/compile: don't inline fn with shape params, but passed no shape arg

[ungerik]

Same problem using 1.18 and 1.18.1 with other similar code. GOEXPERIMENT=unified fixes it.

[heschi]

ping: this is a release blocker that hasn't been updated in a while.