go run ./pkg1

-- go.mod --
module m

go 1.18
-- pkg1/main.go --
package main

import (
	"fmt"
	"os"
	"reflect"

	"m/pkg2"
	"m/pkg3"
)

func main() {
	i1 := pkg3.GetI()
	i2 := pkg2.Inst
	instEqual := i1 == i2
	if !instEqual {
		v1, v2 := reflect.ValueOf(i1), reflect.ValueOf(i2)
		ptrEqual := v1.Pointer() == v2.Pointer()
		typeEqual := v1.Type() == v2.Type()
		if !ptrEqual {
			fmt.Printf("pointer values are unequal\n")
		}
		if !typeEqual {
			fmt.Printf("types are not equal\n\t%v\n\t%v\n", v1.Type(), v2.Type())
		}
		os.Exit(1)
	}
}

-- pkg2/x.go --
package pkg2

import "m/pkg3"

var Inst = pkg3.GetI()

-- pkg3/x.go --
package pkg3

type I interface{}

type impl[P any] struct{
	_ byte
}

var instance = &impl[int]{}

func GetI() I {
	return instance
}

> go run ./pkg1
[stdout]
types are not equal
	*pkg3.impl[int]
	*pkg3.impl[int]

[stderr]
exit status 1