I am receiving below error at mix compile. I tried to downgrade but received error on Mac. Help please…

$ brew switch elixir 1.6.6
Error: elixir does not have a version "1.6.6" in the Cellar.
elixir installed versions: 1.7.4

I am at Elixir 1.7.4 and deps are

      {:absinthe, "~> 1.4.0"},
      {:absinthe_plug, "~> 1.4.0"},
      {:absinthe_ecto, "~> 0.1.3"},

The root query type must be implemented and be a of type Object

  #Example
  defmodule MyApp.Schema do
    use Absinthe.Schema

    query do
      #Fields go here
    end
  end

From the graqhql schema specifiation

A GraphQL schema includes types, indicating where query and mutation
operations start. This provides the initial entry points into the type system.
The query type must always be provided, and is an Object base type. The
mutation type is optional; if it is null, that means the system does not
support mutations. If it is provided, it must be an object base type.

Reference: https://facebook.github.io/graphql/#sec-Initial-types

lib/absinthe/schema.ex:271: Absinthe.Schema.__after_compile__/2
(stdlib) lists.erl:1263: :lists.foldl/3
(stdlib) erl_eval.erl:680: :erl_eval.do_apply/6
(elixir) lib/kernel/parallel_compiler.ex:206: anonymous fn/4 in Kernel.ParallelCompiler.spawn_workers/6