`compatible_intersection/2` invalid for `none()` type

[lukaszsamson]

Existing issue

• I have searched existing issues and could not find a duplicate.

Elixir and Erlang/OTP versions

Erlang/OTP 28 [erts-16.4.0.1] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

Interactive Elixir (1.21.0-dev)

Operating system

any

Current behavior

compatible_intersection/2 doc states

Returns the intersection between two types only if they are compatible. Otherwise returns :error.

yet compatible_intersection(other, :term) shortcut does not check compatibility

Repro:

compatible?(none(), term())
false # correct
compatible?(dynamic(none()), term())
false # correct
compatible_intersection(none(), term())
{:ok, %{}} # wrong, expected error
compatible_intersection(dynamic(none()), term())
{:ok, %{dynamic: %{}}} # wrong, expected error

The bug currently has no impact on real code. The only caller is

elixir/lib/elixir/lib/module/types/of.ex

Line 140 in 4215bbe

case gradual?(old_type) and compatible_intersection(old_type, type) do

where gradual?(old_type) and ew_type != old_type effectively nullify it.

Expected behavior

Error returned