Writing multiple specs for multiple function clauses? Or single spec?

I’m confused… when grooming the docs for https://elixir-lang.org/getting-started/typespecs-and-behaviours.html I got the feedback that multiple function clauses require multiple @specs. But now that I’m digging into dialyzer, I’m getting errors in places where I’ve done that. E.g.

Overloaded contract for MyApp.some_function/1 has
overlapping domains; such contracts are currently unsupported and
are simply ignored.

Consider this module:

defmodule MyApp.Helpers do
  
  alias Absinthe.Blueprint.Input.String, as: AbsintheString
  alias Absinthe.Blueprint.Input.Integer, as: AbsintheInteger
  alias Absinthe.Blueprint.Input.Float, as: AbsintheFloat
  
  @spec parse_value(AbsintheString.t() | AbsintheInteger.t() | AbsintheFloat.t() | any()) :: {:ok, String.t()} | {:error, any()}
  def parse_value(%AbsintheString{value: value}) do
    {:ok, value}
  end
  
  def parse_value(%AbsintheInteger{value: value}) do
    {:ok, Integer.to_string(value)}
  end
  
  def parse_value(%AbsintheFloat{value: value}) do
    {:ok, Float.to_string(value)}
  end


  def parse_value(_) do
    {:error, "Invalid value"}
  end
end

Dialyzer seems happy when it has only a single combined @spec, but readability is better when each function clause has its own @spec, something more like this:

  @spec parse_value(AbsintheString.t()) :: {:ok, String.t()}
  def parse_value(%AbsintheString{value: value}) do
    {:ok, value}
  end

  @spec parse_value(AbsintheInteger.t()) :: {:ok, String.t()}
  def parse_value(%AbsintheInteger{value: value}) do
    {:ok, Integer.to_string(value)}
  end
  # ... etc...

Which way is correct?