Have a look at this: https://github.com/whatyouhide/short_maps

I think just one small change is required:

defmodule DestructingAssignment do
  defmacro __using__(_) do
    quote do: import unquote(__MODULE__)
  end

  defmacro sigil_m({:<<>>, _line, [string]}, []) do
    spec = string
           |> String.split
           |> Stream.map(&String.to_atom/1)
           |> Enum.map(&{&1, {&1, [], nil}})  #=> [foo: {:foo, [], nil}, bar: {:bar, [], nil}]
    {:%{}, [], spec}
  end
end

Works like a charm! But here come a new question, what does the last part of an AST node mean?

According to Saša Jurić’s article about macros, the third part of variable AST represents where the quoting happens. If it’s nil, the identifier is not hygienic. Check out paragraph “Discovering the AST structure” of the article and the series for the detail.

I have no ideas how macros work, but this is very useful and I made a string version also:

  defmacro sigil_d({:<<>>, _line, [string]}, []) do
    spec =
      string
      |> String.split()
      |> Stream.map(&String.to_atom/1) # how could we do without this?
      |> Enum.map(&{to_string(&1), {&1, [], nil}})

    {:%{}, [], spec}
  end

Works great! (so far)

iex(31)> ~d(a) = %{"a" => 5}
%{"a" => 5}
iex(32)> a
5