[denisw]

Could you explain which changes to Elixir 1.5 and OTP 20 should result in better Dialyzer error messages? I didn't find anything relevant to that in the respective changelogs.

(For context, Dialyzer is a static analysis tool detecting type errors which is part of the core Erlang distribution.)

[_asummers]

It's kind of cryptic, but the Erlang release notes say:

  OTP-14369    Application(s): compiler, dialyzer, stdlib
               Related Id(s): PR-1367

               The format of debug information that is stored in BEAM
               files (when debug_info is used) has been changed. The
               purpose of the change is to better support other
               BEAM-based languages such as Elixir or LFE.

               All tools included in OTP (dialyzer, debugger, cover,
               and so on) will handle both the new format and the
               previous format. Tools that retrieve the debug
               information using beam_lib:chunk(Beam, [abstract_code])
               will continue to work with both the new and old format.
               Tools that call beam_lib:chunk(Beam, ["Abst"]) will not
               work with the new format.

               For more information, see the description of debug_info
               in the documentation for beam_lib and the description
               of the {debug_info,{Backend,Data}} option in the
               documentation for compile.

There aren't specific notes in the Elixir 1.5 release notes, but given that it is OTP20 compatible, I assume it would be able to leverage this, perhaps with some work by Dialyxir.

http://erlang.org/download/otp_src_20.0-rc2.readme