Do not crash on invalid imports metadata

Author: josevalim

lib/elixir/src/elixir_dispatch.erl

@@ -329,7 +329,7 @@ find_import_by_name_arity(Tuple, List) ->
 
 is_import(Meta, Arity) ->
   case lists:keyfind(imports, 1, Meta) of
-    {imports, Imports} ->
+    {imports, [_ | _] = Imports} ->
       case lists:keyfind(context, 1, Meta) of
         {context, _} ->
           case lists:keyfind(Arity, 1, Imports) of
@@ -338,7 +338,7 @@ is_import(Meta, Arity) ->
           end;
         false -> false
       end;
-    false -> false
+    _ -> false
   end.
 
 % %% We've reached the macro wrapper fun, skip it with the rest

lib/elixir/test/elixir/kernel/expansion_test.exs

@@ -446,6 +446,11 @@ defmodule Kernel.ExpansionTest do
 
       assert expand(before_expansion) == after_expansion
     end
+
+    test "invalid metadata" do
+      assert expand({:foo, [imports: 2, context: :unknown], [1, 2]}) ==
+               {:foo, [imports: 2, context: :unknown], [1, 2]}
+    end
   end
 
   describe "floats" do