Introduce support for Mod.{A, B, C} on imports, alias, require and use

[lexmag]

Closes #3646.

• adjust elixir_parser to emit new AST
• multi alias

defmodule MultiAlias1 do
  alias List.{Chars}
end

multiline:

defmodule MultiAlias2 do
  alias Mix.{
    CLI,
    Shell.IO
  }
end

just random place:

[List.{Chars}, 1]
** (UndefinedFunctionError) undefined function: List.{}/1
    (elixir) List.{}(Chars)

invalid identifier:

defmodule MultiAlias1 do
  alias List.{Chars, 42}
end
** (SyntaxError) iex:2: syntax error before: '}'

• multi import
• multi require
• multi use

There are a couple of open questions:

• do we need to support trailing comma, e.g.: macro List.{Chars,}
• do we need to support blank import (alias, etc.), e.g.: macro List.{}

@josevalim, I would like any feedback on it.

[josevalim]

I don't think we need to change the parser, I have found this old commit, we just need to bring it back:

b4b9ecc

Except I wouldn't bring [], although we can bring both {} and <<>>. The reason we shouldn't bring [] it is because we don't have :[] in AST anyway.

[josevalim]

We do support options... we don't support :as.

[lexmag]

Updated.

[josevalim]

Try moving the case to a separate function that returns a list. Then you can just do: Enum.map parse_aliases(module, __CALLER__), fun with unquote_splicing at the end.

[josevalim]

Beautiful. It will be in 1.2. :)

[knewter]

o/ \o

[paulcsmith]

This is going to be awesome!

[mschae]

Awesome! This is great news, thanks so much!

Also do you guys (@knewter @paulcsmith and @lexmag) share the same photographer? ;)

[paulcsmith]

@mschae Haha I hadn't noticed that! Maybe we do!

[knewter]

Ha, mine came from a headshot at OSCon 2014...anticipating responses :) /cc @paulcsmith @lexmag

[paulcsmith]

@knewter Got mine when I joined the company I'm working for :)

[lexmag]

Hehe, homemade for visa application about 2 years ago.