Fix redefined function source location (#5720)

When functions are redefined in a different file, the translation uses
the first definition source location for all subsequent definitions.
This manifests itself as warnings that are ascribed to the wrong file.

Fixes #5719

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>

Author: tsubery

lib/elixir/src/elixir_def.erl

@@ -303,12 +303,12 @@ store_each(Check, Kind, File, Location, Module, Defaults, {function, Ann, Name,
 
   {FinalAnn, FinalLocation, FinalDefaults} = case ets:take(Defs, {def, Tuple}) of
     [{_, StoredKind, StoredAnn, StoredFile, StoredCheck,
-        StoredLocation, {StoredDefaults, LastHasBody, LastDefaults}}] ->
+        _StoredLocation, {StoredDefaults, LastHasBody, LastDefaults}}] ->
       check_valid_kind(Ann, File, Name, Arity, Kind, StoredKind),
       (Check and StoredCheck) andalso
         check_valid_clause(Ann, File, Name, Arity, Kind, Data, StoredAnn, StoredFile),
       check_valid_defaults(Ann, File, Name, Arity, Kind, Defaults, StoredDefaults, LastDefaults, LastHasBody),
-      {StoredAnn, StoredLocation, {max(Defaults, StoredDefaults), HasBody, Defaults}};
+      {StoredAnn, Location, {max(Defaults, StoredDefaults), HasBody, Defaults}};
     [] ->
       {Ann, Location, {Defaults, HasBody, Defaults}}
   end,

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

@@ -28,6 +28,31 @@ defmodule Kernel.WarningTest do
     purge Sample
   end
 
+  test "unused variable in redefined function in different file" do
+    output = capture_err(fn ->
+      Code.eval_string """
+      defmodule Sample do
+        defmacro __using__(_) do
+          quote location: :keep do
+            def function(arg)
+          end
+        end
+      end
+      """
+      Code.eval_string("""
+      defmodule RedefineSample do
+        use Sample
+        def function(var123), do: nil
+      end
+      """, [], file: "redefine_sample.ex")
+    end)
+    assert output =~ "redefine_sample.ex:3"
+    assert output =~ "variable \"var123\" is unused"
+  after
+    purge Sample
+    purge RedefineSample
+  end
+
   test "useless literal" do
     message = "code block contains unused literal \"oops\""