Fix IEx.h/1 macro spec introspection

lib/iex/lib/iex/introspection.ex

@@ -610,10 +610,15 @@ defmodule IEx.Introspection do
   end
 
   defp get_spec(module, name, arity) do
+    macro? = macro_exported?(module, name, arity)
+    name_arity = if macro?, do: {:elixir_utils.macro_name(name), arity + 1}, else: {name, arity}
+
     with {:ok, all_specs} <- Typespec.fetch_specs(module),
-         {_, specs} <- List.keyfind(all_specs, {name, arity}, 0) do
+         {_, specs} <- List.keyfind(all_specs, name_arity, 0) do
       formatted =
         Enum.map(specs, fn spec ->
+          spec = if macro?, do: unpack_caller(spec), else: spec
+
           Typespec.spec_to_quoted(name, spec)
           |> format_typespec(:spec, 2)
         end)

lib/iex/test/iex/helpers_test.exs

@@ -516,6 +516,13 @@ defmodule IEx.HelpersTest do
       assert capture_io(fn -> h(IEx.Helpers.recompile() / 1) end) =~ spec
     end
 
+    test "prints spec for default arg macro" do
+      spec = "@spec compile_env(app(), key() | list(), value()) :: value()"
+
+      assert capture_io(fn -> h(Application.compile_env() / 2) end) =~ spec
+      assert capture_io(fn -> h(Application.compile_env() / 3) end) =~ spec
+    end
+
     test "prints sigil documentation" do
       assert capture_io(fn -> h(~w//) end) =~ "Handles the sigil `~w` for list of words"
     end