nested routes and routes helper path

gistfile1.txt

#routes
resources "/projects", ProjectController do
  resources "/budgets", BudgetController
end
#budget_view.ex

defmodule ProjexWeb.ProjectView do
    use ProjexWeb, :view
end

#budget_view.ex

defmodule ProjexWeb.BudgetView do
    use ProjexWeb, :view
end

# project_controller.ex
...
def show(conn, %{"id" => id})do
      project = Programs.get_project!(id)
      budget = Programs.get_budget!(id)
      render(conn, "show.html", project: project, budget: budget)
end
...
# budget_controller.ex
...
def show(conn, %{"project_id" => project_id, "id" => id}) do
      project = Programs.get_project!(project_id)
      render(conn, "show.html", project: project, budget: id)
end
...
# budget/show.html.eex
<h2>Show Budget</h2>

<%= @project.name %>
<%= @budget %>

#project/show.html.eex
<h2>Scheda progetto</h2>

<p><strong>Titolo progetto:</strong> <%= @project.name %></p>
<p><strong>Breve descrizione:</strong><%= @project.description %></p>
<p><strong>Inizio progetto:</strong><%= @project.start_date %></p>
<p><strong>Fine progetto:</strong><%= @project.end_date %></p>
<%= link "show", to: Routes.project_budget_path(@conn, :show, @project, @budget) %> #This line is causing troubles

# THIS IS THE ERROR

ArgumentError at GET /projects/1
assign @budget not available in eex template.
Please make sure all proper assigns have been set. If this
is a child template, ensure assigns are given explicitly by
the parent template as they are not automatically forwarded.

Available assigns: [:conn, :project, :view_module, :view_template]