`URI.parse` has incorrect type spec for `path`

[breunigs]

Environment

Erlang/OTP 24 [erts-12.1.4] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit]
Elixir 1.13.0-rc.1 (0974e90) (compiled with Erlang/OTP 22

Current behavior

iex(2)> URI.parse("http://")
%URI{
  authority: "",
  fragment: nil,
  host: "",
  path: nil, # it's nil
  port: 80,
  query: nil,
  scheme: "http",
  userinfo: nil
}

however:

iex(6)> t URI  
@opaque authority()

@type t() :: %URI{
        authority: authority(),
        fragment: nil | binary(),
        host: nil | binary(),
        path: binary(), # it can't be nil
        port: nil | :inet.port_number(),
        query: nil | binary(),
        scheme: nil | binary(),
        userinfo: nil | binary()
      }

In my 1.12 code I had a nil check for path, since it can be nil. When updating, Dialyzer complained that this check can never succeed -- and according to the type spec that's true:

dummy.ex:2:guard_fail
The guard clause:

when _ :: binary() === nil

can never succeed.

However, removing it of course will cause issues down the line.

Expected behavior

I don't really have a desired behaviour. The angle I'm coming from is that URI.parse was only mentioned as a soft-deprecation, so I expected that my existing code keeps working, including type-checks. So simply updating the changelog would be fine by me. I guess removing the type-spec from URI.parse also works.

related: #11363