Theoretical mix task that will fail/alert when new Dialyzer errors are added to codebase. Based on: https://www.youtube.com/watch?v=4PZE40h13wM

check_types.ex

defmodule Mix.Tasks.CheckTypes do
  @moduledoc "The checktypes mix task: `mix help checktypes`"
  
  use Mix.Task

  @shortdoc "Runs Dialyzer and compares the results to our existing errors."
  def run(_args) do
    # https://github.com/jeremyjh/dialyxir/blob/ed0df656a74eb6d4e906fe20fc056ca42ba7d5ec/lib/mix/tasks/dialyzer.ex#L145-L155
    output = Mix.Task.run("dialyzer", ["--quiet", "--format", "ignore_file"])
    
    # TODO: 1. Parse text output from dialyzer into list of Dialyzer error tuples.
    # TODO: 2. Compare the list of old errors and list of new errors.
    # TODO: 3. If any new errors have been added, fail.
    # TODO: 4. If lists are equal or list of new errors is smaller, succeed.
    # TODO: 5. As old errors are fixed, devs will remove lines from below list so they aren't checked in the future.
  end

  def old_type_check_errors() do
    [
      # Huge list of Dialyzer error tuples
    ]
  end
end