go build main.go
! stdout .
! stderr .

-- main.go --
package main

import (
	"demo/registry"
)

func main() {
	_ = registry.NewUserRegistry()
}

-- go.mod --
module demo

go 1.24

-- model/user.go --
package model

type User struct {
	ID int
}

func (c *User) String() string {
	return ""
}

-- ordered/map.go --
package ordered

type OrderedMap[K comparable, V any] struct {
	m map[K]V
}

func New[K comparable, V any](options ...any) *OrderedMap[K, V] {
	orderedMap := &OrderedMap[K, V]{}
	return orderedMap
}

-- registry/user.go --
package registry

import (
	"demo/model"
	"demo/ordered"
)

type baseRegistry = Registry[model.User, *model.User]

type UserRegistry struct {
	*baseRegistry
}

type Registry[T any, P PStringer[T]] struct {
	m *ordered.OrderedMap[string, P]
}

type PStringer[T any] interface {
	*T
	String() string
}

func NewRegistry[T any, P PStringer[T]]() *Registry[T, P] {
	r := &Registry[T, P]{
		m: ordered.New[string, P](),
	}
	return r
}

func NewUserRegistry() *UserRegistry {
	return &UserRegistry{
		baseRegistry: NewRegistry[model.User](),
	}
}