cmd/compile: ICE when unpacking arguments of variadic generic function

[sonlamho]

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

$ go version
go version go1.18 linux/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="/home/holamson/.cache/go-build"
GOENV="/home/holamson/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/holamson/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/holamson/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/holamson/.local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/holamson/.local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
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 -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1142584741=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Link on go.dev/play: https://go.dev/play/p/VgkIIishLsB

Complete runnable program:

package main

import "fmt"

type IntLike interface {
	~int | ~int64 | ~int32 | ~int16 | ~int8
}

func Reduce[T any, U any, Uslice ~[]U](function func(T, U) T, sequence Uslice, initial T) T {
	result := initial
	for _, x := range sequence {
		result = function(result, x)
	}
	return result
}

func min[T IntLike](x, y T) T {
	if x < y {
		return x
	}
	return y

}

// Min returns the minimum element of `nums`.
func Min[T IntLike, NumSlice ~[]T](nums NumSlice) T {
	if len(nums) == 0 {
		return T(0)
	}
	return Reduce(min[T], nums, nums[0])
}

// VarMin is the variadic version of Min.
func VarMin[T IntLike](nums ...T) T {
	return Min(nums)
}

type myInt int

func main() {
	fmt.Println(VarMin(myInt(1), myInt(2))) // OK

	seq := []myInt{1, 2}
	fmt.Println(Min(seq))       // OK
	fmt.Println(VarMin(seq...)) // ERROR

}

What did you expect to see?

Expected output:

1
1
1

What did you see instead?

./prog.go:46:20: internal compiler error: assigning nums (type []myInt) to parameter nums (type go.shape.[]int_1)

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

Go build failed.

[mknyszek]

CC @griesemer @findleyr

[mknyszek]

CC @dr2chase

[ianlancetaylor]

CC @randall77

[findleyr]

The error message here looks similar to #51909, though I have not confirmed that this is a dupe.

[mdempsky]

Prints the expected output with GOEXPERIMENT=unified.