Optional arguments must be counted from the end, closes #10095

Author: josevalim

lib/elixir/src/elixir_locals.erl

@@ -118,11 +118,11 @@ format_error({function_conflict, {Receiver, {Name, Arity}}}) ->
 format_error({unused_args, {Name, Arity}}) ->
   io_lib:format("default values for the optional arguments in ~ts/~B are never used", [Name, Arity]);
 
-format_error({unused_args, {Name, Arity}, 1}) ->
-  io_lib:format("the default value for the first optional argument in ~ts/~B is never used", [Name, Arity]);
+format_error({unused_args, {Name, Arity}, Count}) when Arity - Count == 1 ->
+  io_lib:format("the default value for the last optional argument in ~ts/~B is never used", [Name, Arity]);
 
 format_error({unused_args, {Name, Arity}, Count}) ->
-  io_lib:format("the default values for the first ~B optional arguments in ~ts/~B are never used", [Count, Name, Arity]);
+  io_lib:format("the default values for the last ~B optional arguments in ~ts/~B are never used", [Arity - Count, Name, Arity]);
 
 format_error({unused_def, {Name, Arity}, defp}) ->
   io_lib:format("function ~ts/~B is unused", [Name, Arity]);

lib/elixir/test/elixir/kernel/warning_test.exs

@@ -563,17 +563,17 @@ defmodule Kernel.WarningTest do
              end
              """)
            end) =~
-             "the default values for the first 2 optional arguments in b/3 are never used\n  nofile:3"
+             "the default value for the last optional argument in b/3 is never used\n  nofile:3"
 
     assert capture_err(fn ->
              Code.eval_string(~S"""
              defmodule Sample3 do
-               def a, do: b(1)
-               defp b(arg1 \\ 1, arg2 \\ 2, arg3 \\ 3), do: [arg1, arg2, arg3]
+               def a, do: b(1, 2)
+               defp b(arg1, arg2 \\ 2, arg3 \\ 3, arg4 \\ 4), do: [arg1, arg2, arg3, arg4]
              end
              """)
            end) =~
-             "the default value for the first optional argument in b/3 is never used\n  nofile:3"
+             "the default values for the last 2 optional arguments in b/4 are never used"
 
     assert capture_err(fn ->
              Code.eval_string(~S"""
@@ -587,27 +587,16 @@ defmodule Kernel.WarningTest do
     assert capture_err(fn ->
              Code.eval_string(~S"""
              defmodule Sample5 do
-               def a, do: b(1, 2, 3)
-               defp b(arg1 \\ 1, arg2 \\ 2, arg3 \\ 3)
-
-               defp b(arg1, arg2, arg3), do: [arg1, arg2, arg3]
-             end
-             """)
-           end) =~ "default values for the optional arguments in b/3 are never used\n  nofile:3"
-
-    assert capture_err(fn ->
-             Code.eval_string(~S"""
-             defmodule Sample6 do
                def a, do: b(1, 2)
                defp b(arg1 \\ 1, arg2 \\ 2, arg3 \\ 3)
 
                defp b(arg1, arg2, arg3), do: [arg1, arg2, arg3]
              end
              """)
            end) =~
-             "the default values for the first 2 optional arguments in b/3 are never used\n  nofile:3"
+             "the default value for the last optional argument in b/3 is never used\n  nofile:3"
   after
-    purge([Sample1, Sample2, Sample3, Sample4, Sample5, Sample6])
+    purge([Sample1, Sample2, Sample3, Sample4, Sample5])
   end
 
   test "unused import" do