Compiler crash in type checker when using logical operator with equality guard

[aleagnelli]

Elixir and Erlang/OTP versions

Erlang/OTP 28 [erts-16.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit]

Elixir 1.20.0-rc.4 (5d794ab) (compiled with Erlang/OTP 28)

Operating system

macOS Taohe 26.3.1

Current behavior

the following guard crash the compilation

defmodule Bug do
  def do_stuff(a, b, c) when a != (b or c) do
    :ok
  end
end

== and and have the same behaviour

== Compilation error in file lib/bug.ex ==
** (RuntimeError) found error while checking types for Bug.do_stuff/3:

** (BadMapError) expected a map, got:

    nil

The exception happened while checking this code:

def do_stuff(a, b, c) when :erlang."/="(a, :erlang.orelse(b, c)) do
  :ok
end

Please report this bug at: https://github.com/elixir-lang/elixir/issues

    (elixir 1.20.0-rc.4) lib/module/types/pattern.ex:1064: Module.Types.Pattern.enable_conditional_mode/1
    (elixir 1.20.0-rc.4) lib/module/types/pattern.ex:1292: Module.Types.Pattern.of_remote/6
    (elixir 1.20.0-rc.4) lib/module/types/pattern.ex:511: Module.Types.Pattern.of_pattern_tree/3
    (elixir 1.20.0-rc.4) lib/module/types/pattern.ex:124: anonymous fn/6 in Module.Types.Pattern.of_changed_var/3
    (elixir 1.20.0-rc.4) lib/enum.ex:2617: Enum."-reduce/3-lists^foldl/2-0-"/3
    (elixir 1.20.0-rc.4) lib/module/types/pattern.ex:122: Module.Types.Pattern.of_changed_var/3
    (elixir 1.20.0-rc.4) lib/module/types/pattern.ex:110: anonymous fn/3 in Module.Types.Pattern.of_changed_deps/4
    (stdlib 7.3) maps.erl:894: :maps.fold_1/4

the following variants compile:
when a != b
when (a and not (b and c)) or (not a and (b or c))
when (a and not (b and c)) != (not a and (b or c))

Expected behavior

compilation successful

[gldubc]

Seems to happen when or is on the right-hand side of a comparison (a == (b or c), a !== (b or c), also a == hd(b or c)). It also bugs with and: a == (b and c). Looking into it.

[aleagnelli]

Also happen if the logical operator is on the left-hand side of the comparison like (a or b) == c

[gldubc]

You're right! #15257 fixes both cases. :)