cmd/compile: internal compiler error: OCONVIFACE can't operate on an empty interface

[mmrath]

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

$ go version
go version devel go1.18-c84f3a4004 Thu Sep 9 04:47:41 2021 +0000 darwin/amd64

Does this issue reproduce with the latest release?

No. I am using a version built from today's master

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

go env Output

$ go env
O111MODULE=""

GOARCH="amd64"

GOBIN=""

GOCACHE="/Users/myusername/Library/Caches/go-build"

GOENV="/Users/myusername/Library/Application Support/go/env"

GOEXE=""

GOFLAGS=""

GOHOSTARCH="amd64"

GOHOSTOS="darwin"

GOINSECURE=""

GOMODCACHE="/Users/myusername/go/pkg/mod"

GONOPROXY=""

GONOSUMDB=""

GOOS="darwin"

GOPATH="/Users/myusername/go"

GOPRIVATE=""

GOPROXY="https://proxy.golang.org,direct"

GOROOT="/Users/myusername/Projects/golang-src"

GOSUMDB="sum.golang.org"

GOTMPDIR=""

GOTOOLDIR="/Users/myusername/Projects/golang-src/pkg/tool/darwin_amd64"

GOVCS=""

GOVERSION="go1.16.7"

GCCGO="gccgo"

AR="ar"

CC="clang"

CXX="clang++"

CGO_ENABLED="1"

GOMOD="/Users/myusername/Projects/golang-src/src/go.mod"

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/y4/b5zhbtf93r90hfy7gn1c2sjm0000gn/T/go-build2360186774=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Compile and run the code below using go run

package main

import "fmt"

func main() {
	IsZero[interface{}]("")
}

func IsZero[T comparable](val T) bool {
	var zero T
	fmt.Printf("%v:%v", zero, val)
	return val != zero
}

What did you expect to see?

Compile and run successfully or give a valid error

What did you see instead?

# command-line-arguments
./main.go:11:13: internal compiler error: OCONVIFACE can't operate on an empty interface

goroutine 1 [running]:
runtime/debug.Stack()
	/Users/myusername/Projects/golang-src/src/runtime/debug/stack.go:24 +0x65
cmd/compile/internal/base.FatalfAt({0x401810, 0xc0}, {0x19103ae, 0x2e}, {0x0, 0x0, 0x0})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/base/print.go:227 +0x154
cmd/compile/internal/base.Fatalf(...)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/base/print.go:196
cmd/compile/internal/walk.walkConvInterface(0xc000439180, 0xc00042ef20)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/convert.go:65 +0x155
cmd/compile/internal/walk.walkExpr1({0x1a68cd0, 0xc000439180}, 0xc000439180)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/expr.go:211 +0x57f
cmd/compile/internal/walk.walkExpr({0x1a68cd0, 0xc000439180}, 0xc00042ef20)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/expr.go:55 +0x428
cmd/compile/internal/walk.walkAssign(0xc00042ef20, {0x1a68370, 0xc000741c70})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/assign.go:72 +0x9dc
cmd/compile/internal/walk.walkExpr1({0x1a68370, 0xc000741c70}, 0xc000741c70)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/expr.go:179 +0x43f
cmd/compile/internal/walk.walkExpr({0x1a68370, 0xc000741c70}, 0xc00042ef20)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/expr.go:55 +0x428
cmd/compile/internal/walk.walkStmt({0x1a68370, 0xc000741c70})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/stmt.go:57 +0x5da
cmd/compile/internal/walk.walkStmtList({0xc00008f2d0, 0x1, 0x0})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/stmt.go:167 +0x5b
cmd/compile/internal/walk.walkStmt({0x1a685c8, 0xc000472f80})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/stmt.go:98 +0x1a5
cmd/compile/internal/walk.slicelit(0x0, 0xc000446080, {0x1a69d38, 0xc00007f6c0}, 0xc00042f740)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/complit.go:405 +0xc6d
cmd/compile/internal/walk.anylit({0x1a68b40, 0xc000446080}, {0x1a69d38, 0xc00007f6c0}, 0xc00042f380)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/complit.go:592 +0x4c5
cmd/compile/internal/walk.oaslit(0xc000741a40, 0xc00007f6c0)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/complit.go:635 +0x198
cmd/compile/internal/walk.walkAssign(0xc00042f740, {0x1a68370, 0xc000741a40})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/assign.go:57 +0x5eb
cmd/compile/internal/walk.walkExpr1({0x1a68370, 0xc000741a40}, 0xc000741a40)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/expr.go:179 +0x43f
cmd/compile/internal/walk.walkExpr({0x1a68370, 0xc000741a40}, 0xc00042f740)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/expr.go:55 +0x428
cmd/compile/internal/walk.appendWalkStmt(0xc00042f740, {0x1a68370, 0xc000741a40})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/walk.go:256 +0x65
cmd/compile/internal/walk.ascompatee(0x16, {0xc00073afc0, 0x400, 0x1a69d38}, {0xc00073af80, 0xc0004390e0, 0x239a500})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/assign.go:372 +0x6fc
cmd/compile/internal/walk.walkAssignList(0xc00042fa80, 0xc0000939e0)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/assign.go:146 +0x12f
cmd/compile/internal/walk.walkExpr1({0x1a681e0, 0xc0000939e0}, 0xc0000939e0)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/expr.go:183 +0x325
cmd/compile/internal/walk.walkExpr({0x1a681e0, 0xc0000939e0}, 0xc00042fa80)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/expr.go:55 +0x428
cmd/compile/internal/walk.walkStmt({0x1a681e0, 0xc0000939e0})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/stmt.go:57 +0x5da
cmd/compile/internal/walk.walkStmtList({0xc000716400, 0x17, 0xc0000766e0})
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/stmt.go:167 +0x5b
cmd/compile/internal/walk.Walk(0xc0000766e0)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/walk/walk.go:43 +0xef
cmd/compile/internal/gc.prepareFunc(0xc0000766e0)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/gc/compile.go:92 +0x6d
cmd/compile/internal/gc.enqueueFunc(0xc0000766e0)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/gc/compile.go:66 +0x2fd
cmd/compile/internal/gc.Main(0x191ef50)
	/Users/myusername/Projects/golang-src/src/cmd/compile/internal/gc/main.go:303 +0xe94
main.main()
	/Users/myusername/Projects/golang-src/src/cmd/compile/main.go:55 +0xdd

[cuonglm]

cc @randall77 @danscales

[cuonglm]

git bisect points to https://go-review.googlesource.com/c/go/+/344830

[gopherbot]

Change https://golang.org/cl/348736 mentions this issue: cmd/compile: stenciled conversions might be NOPs