Destructing assignment

Questions & Help Questions
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1

I want to mimic ES6’s destructing assignment using Elixir’s sigil.

What I want to achieve is

~m{foo bar} = %{foo: 1, bar: 2}
foo  #=> 1
bar  #=> 2

So far I have the following code

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, [], Elixir}})  #=> [foo: {:foo, [], Elixir}, bar: {:bar, [], Elixir}]
    {:%{}, [], spec}
  end
end

When I run ~m{foo bar} = %{foo: 1, bar: 2}, pattern matching succeeds. But when I try to read the variable foo, it gives me

warning: variable "foo" does not exist and is being expanded to "foo()", please use parentheses to remove the ambiguity or change the variable name
  iex:9

** (CompileError) iex:9: undefined function foo/0

I guess this is due to the macro hygiene, but as you can see, the sigil implementation doesn’t use quote. How can I inject local variable to the macro’s caller’s scope?