Endless loop when collecting into a map

[lukaszsamson]

Elixir and Erlang/OTP versions

Erlang/OTP 26 [erts-14.2.5.8] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

Elixir 1.18.2 (compiled with Erlang/OTP 26)

Operating system

macOS

Current behavior

This code hangs both in tests and iex

for k <- [:foo, :__struct__], into: %{}, do: {k, nil} 

The same code does not hang for other atoms (false, true) and values

Expected behavior

No hang and %{foo: nil, __struct__: nil} returned or ArgumentError.

[lukaszsamson]

This also hangs:

%{__struct__: nil}

[sabiwara]

Seems to be when dispatching any protocol to %{__struct__: nil}:

• inspect(%{__struct__: nil})
• Enum.to_list(%{__struct__: nil})

iex> Inspect.impl_for %{__struct__: nil}
Inspect
# should be: Inspect.Any

[josevalim]

We should fix so the concatenation returns Inspect.nil. I don't think we should special case any atom. :)

[josevalim]

I will push a fix since I want to ship a new v1.18 :)