cmd/compile: internal compiler error: InitTodoFunc still has declarations (with -G=3)

[mccolljr]

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

$ go version
go version devel go1.17-105a6e9518 Fri Apr 23 11:33:03 2021 +0000 darwin/amd6

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/jmccollum/Library/Caches/go-build"
GOENV="/Users/jmccollum/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/jmccollum/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/jmccollum/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/Users/jmccollum/go/src/github.com/golang/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/Users/jmccollum/go/src/github.com/golang/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="devel go1.17-105a6e9518 Fri Apr 23 11:33:03 2021 +0000"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/jmccollum/go/src/github.com/golang/go/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/0d/ncmx73fn4s1_n9bz83jdl0lh0000gn/T/go-build2307230618=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

package main

import (
	"fmt"
	"log"
)

func try[T any](v T, err error) T {
	if err != nil {
		panic(err)
	}
	return v
}

func handle(handle func(error)) {
	if issue := recover(); issue != nil {
		if e, ok := issue.(error); ok && e != nil {
			handle(e)
		} else {
			handle(fmt.Errorf("%v", e))
		}
	}
}

func main() {
	defer handle(func(e error) { log.Fatalln(e) })
	_ = try(fmt.Println("test"))
}

What did you expect to see?

Program compiles and runs with no output

What did you see instead?

Program fails to compile with an internal compiler error:

<unknown line number>: internal compiler error: InitTodoFunc still has declarations

goroutine 1 [running]:
runtime/debug.Stack()
        /Users/jmccollum/go/src/github.com/golang/go/src/runtime/debug/stack.go:24 +0x65
cmd/compile/internal/base.FatalfAt({0xa2b00, 0xc0}, {0x1934032, 0x191a737}, {0x0, 0x10000000100cc5b, 0x22097f0})
        /Users/jmccollum/go/src/github.com/golang/go/src/cmd/compile/internal/base/print.go:227 +0x157
cmd/compile/internal/base.Fatalf(...)
        /Users/jmccollum/go/src/github.com/golang/go/src/cmd/compile/internal/base/print.go:196
cmd/compile/internal/pkginit.Task()
        /Users/jmccollum/go/src/github.com/golang/go/src/cmd/compile/internal/pkginit/init.go:66 +0x8b6
cmd/compile/internal/gc.Main(0x1949ab8)
        /Users/jmccollum/go/src/github.com/golang/go/src/cmd/compile/internal/gc/main.go:197 +0xb38
main.main()
        /Users/jmccollum/go/src/github.com/golang/go/src/cmd/compile/main.go:55 +0xdd

[mccolljr]

This is the code section that is originating the panic:

go/src/cmd/compile/internal/pkginit/init.go

Lines 62 to 67 in a956a0e

	if typecheck.InitTodoFunc.Dcl != nil {
	// We only generate temps using InitTodoFunc if there
	// are package-scope initialization statements, so
	// something's weird if we get here.
	base.Fatalf("InitTodoFunc still has declarations")
	}

I will do a bit more digging.

[mccolljr]

This is being generated directly from gc.Main:

go/src/cmd/compile/internal/gc/main.go

Lines 196 to 199 in 95ed5c3

	// Build init task.
	if initTask := pkginit.Task(); initTask != nil {
	typecheck.Export(initTask)
	}

The decls that are causing the panic seem to be either the results of fmt.Println("test") in the call _ = try(fmt.Println("test")) or the arguments to the try[int] instantiation of try[T] from that call:

.   NAME-main..autotmp_0 esc(N) Class:PAUTO Offset:0 AutoTemp OnStack Used int
.   NAME-main..autotmp_1 esc(N) Class:PAUTO Offset:0 AutoTemp OnStack Used error

[cherrymui]

cc @griesemer @mdempsky @findleyr

[griesemer]

Clearly related to the new code dealing with generic functions. Replacing the generic try function with:

func try(v int, err error) int {
	if err != nil {
		panic(err)
	}
	return v
}

makes the error go away.

[gopherbot]

Change https://golang.org/cl/313869 mentions this issue: cmd/compile: fix handling of ir.CurFunc during stenciling