Support Erlang 21 new features

[josevalim]

To be implemented when Erlang 21 is released (part of v1.7):

• Support new handle_continue/2 gen_server callback
• Support the __STACKTRACE__ variable in catch and rescue and Erlang's new try/catch clauses
• Deprecate System.stacktrace outside of catch and rescue
• Integrate with the new logger API (done on v1.6.6)

To be implemented when we require Erlang 21 exclusively:

• Unify :logger and Logger metadata (done in Use Erlang's logger as main logging implementation #9333)
• Remove assert_no_null_byte from file operations and get_env/put_env (find_executable and cmd still need it)
• Optimize elixir_erl_try.erl by removing old stacktrace logic and unifying all clauses into a single one with map_get
• Add is_struct/1 and is_struct/2
• Add is_map_key/2

[OvermindDL1]

Use the new compile_info compiler option to attach Elixir compiler metadata

No way of doing that when building on OTP21 as it stands before it is required?

[josevalim]

We need to check the version because otherwise the data ends up in compile_info but in the wrong place (under options).

[michalmuskala]

I wonder about support for map.field in guards - this requires introducing the map_get guard to Elixir. In the past we haven't introduced new guard functions until all supported versions had them (see ceil/1 and floor/1 we still don't support because we support OTP 19).

[gerhard]

Could this error be related? rabbitmq/rabbitmq-server-boshrelease@0d23f39

We're hitting it on OTP 21.0-rc1 with RabbitMQ 3.7.4 which is using Elixir 1.6.0

cc @hairyhum @michaelklishin @dumbbell

[michalmuskala]

Yes. Elixir does not support OTP 21 yet, some failures are expected.

[michalmuskala]

An additional thing is map iterators - many functions in the erlang's maps module accept either a map or a map iterator. Should we extend our Map module in the same way?

[josevalim]

@michalmuskala that's a good point. I think we can wait for some usage patterns to emerge before actually adding it to the language.

[josevalim]

Relevant discussion here: https://elixirforum.com/t/discussion-incorporating-erlang-otp-21-map-guards-in-elixir/14816

[Jancd]

When I try to run Elixir from source,an error occured after running make test:

{"init terminating in do_boot",{'cannot get bootfile','no_dot_erlang.boot'}}
init terminating in do_boot ({cannot get bootfile,no_dot_erlang.boot})

Crash dump is being written to: erl_crash.dump...done
make: *** [lib/elixir/src/elixir_parser.erl] Error 1

Erlang/OTP version:Erlang/OTP 21 [erts-10.0] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe],and OS :CentOS7.

[josevalim]

@7ethan how have you installed Erlang? Also see this issue: #7794 (comment)

[Jancd]

oh,got it.