Inspect :... and :foo@bar as valid atoms

Author: José Valim

lib/elixir/lib/inspect.ex

@@ -100,7 +100,7 @@ defimpl Inspect, for: Atom do
       valid_ref_identifier?(binary) ->
         "Elixir." <> rest = binary
         rest
-      atom in [:{}, :<<>>] ->
+      atom in [:{}, :<<>>, :...] ->
         ":" <> binary
       atom in Macro.binary_ops or atom in Macro.unary_ops ->
         ":" <> binary
@@ -127,16 +127,21 @@ defimpl Inspect, for: Atom do
   # Detect if atom
 
   defp valid_atom_identifier?(<<h, t :: binary>>) when h in ?a..?z or h in ?A..?Z or h == ?_ do
-    case valid_identifier?(t) do
-      <<>>   -> true
-      <<??>> -> true
-      <<?!>> -> true
-      _      -> false
-    end
+    valid_atom_piece?(t)
   end
 
   defp valid_atom_identifier?(_), do: false
 
+  defp valid_atom_piece?(t) do
+    case valid_identifier?(t) do
+      <<>>              -> true
+      <<??>>            -> true
+      <<?!>>            -> true
+      <<?@, t::binary>> -> valid_atom_piece?(t)
+      _                 -> false
+    end
+  end
+
   defp valid_identifier?(<<h, t :: binary>>)
       when h in ?a..?z
       when h in ?A..?Z

lib/elixir/test/elixir/inspect_test.exs

@@ -37,11 +37,22 @@ defmodule Inspect.AtomTest do
   end
 
   test :op do
-    assert inspect(:@)   == ":@"
+    assert inspect(:+)   == ":+"
     assert inspect(:&&&) == ":&&&"
     assert inspect(:~~~) == ":~~~"
   end
 
+  test :... do
+    assert inspect(:...) == ":..."
+  end
+
+  test :@ do
+    assert inspect(:@) == ":@"
+    assert inspect(:foo@bar) == ":foo@bar"
+    assert inspect(:foo@bar@) == ":foo@bar@"
+    assert inspect(:foo@bar@baz) == ":foo@bar@baz"
+  end
+
   test :container do
     assert inspect(:<<>>) == ":<<>>"
     assert inspect(:{})   == ":{}"