Only warn for commas at the end of words

Author: josevalim

lib/elixir/lib/kernel.ex

@@ -5388,7 +5388,8 @@ defmodule Kernel do
       true ->
         parts = String.split(string)
 
-        parts_with_trailing_comma = :lists.filter(&(:binary.last(&1) == ?,), parts)
+        parts_with_trailing_comma =
+          :lists.filter(&(byte_size(&1) > 1 and :binary.last(&1) == ?,), parts)
 
         if parts_with_trailing_comma != [] do
           stacktrace = Macro.Env.stacktrace(caller)

lib/elixir/test/elixir/kernel/sigils_test.exs

@@ -66,6 +66,7 @@ bar) in ["foo\\\nbar", "foo\\\r\nbar"]
 
   test "sigil w" do
     assert ~w() == []
+    assert ~w([ , ]) == ["[", ",", "]"]
     assert ~w(foo bar baz) == ["foo", "bar", "baz"]
     assert ~w(foo #{:bar} baz) == ["foo", "bar", "baz"]
 
@@ -100,6 +101,7 @@ bar) in ["foo\\\nbar", "foo\\\r\nbar"]
 
   test "sigil W" do
     assert ~W() == []
+    assert ~W([ , ]) == ["[", ",", "]"]
     assert ~W(foo #{bar} baz) == ["foo", "\#{bar}", "baz"]
 
     assert ~W(foo\ bar) == ["foo\\", "bar"]