Compilation error on higher-order functions

Compiling the following fails:

```
defmodule Foo do
  @spec foo((() -> [ integer ])) :: integer
  def foo(_x) do
    1
  end
end
```

With the error:

```
** (CompileError) foo.exs: type '__block__'(_) undefined
```

This seems to be triggered by the list, that is, compiling the following works:

```
defmodule Foo do
  @spec foo((() -> integer)) :: integer
  def foo(_x) do
    1
  end
end
```
