Fix failures

Author: josevalim

lib/elixir/lib/protocol.ex

@@ -631,10 +631,17 @@ defmodule Protocol do
         {[Module.Types.Of.impl(impl)], Descr.atom([Module.concat(protocol, impl)])}
       end)
 
+    # TODO: Test a protocol with no implementation
     domain =
-      clauses
-      |> Enum.map(fn {[domain], _} -> domain end)
-      |> Enum.reduce(&Descr.union/2)
+      case clauses do
+        [] ->
+          Descr.none()
+
+        _ ->
+          clauses
+          |> Enum.map(fn {[domain], _} -> domain end)
+          |> Enum.reduce(&Descr.union/2)
+      end
 
     not_domain = Descr.negation(domain)
 

lib/ex_unit/test/ex_unit/formatter_test.exs

@@ -507,8 +507,8 @@ defmodule ExUnit.FormatterTest do
     defstruct key: 0
 
     defimpl Inspect do
-      def inspect(struct, opts) when is_atom(opts) do
-        struct.unknown
+      def inspect(_struct, opts) when is_atom(opts) do
+        raise "the clause above should never match"
       end
     end
   end