Use head definition meta to warn about unused args (#8198)

Fixes #8184

2 files changed, 68 insertions, 24 deletions

diff --git a/lib/elixir/src/elixir_def.erl b/lib/elixir/src/elixir_def.erl
index 24fca3410..e5b36f28e 100644
--- a/lib/elixir/src/elixir_def.erl
+++ b/lib/elixir/src/elixir_def.erl
@@ -65,17 +65,17 @@ fetch_definitions(File, Module) ->
   {All, Unreachable}.
 
 fetch_definition([Tuple | T], File, Module, Set, Bag, All, Private) ->
-  [{_, Kind, Meta, _, Check, {Defaults, _, _}}] = ets:lookup(Set, {def, Tuple}),
+  [{_, Kind, Meta, _, Check, {MaxDefaults, _, Defaults}}] = ets:lookup(Set, {def, Tuple}),
 
   try ets:lookup_element(Bag, {clauses, Tuple}, 2) of
     Clauses ->
       NewAll =
-        [{Tuple, Kind, add_defaults_to_meta(Defaults, Meta), Clauses} | All],
+        [{Tuple, Kind, add_defaults_to_meta(MaxDefaults, Meta), Clauses} | All],
       NewPrivate =
         case (Kind == defp) orelse (Kind == defmacrop) of
           true ->
-            WarnMeta = case Check of true -> Meta; false -> false end,
-            [{Tuple, Kind, WarnMeta, Defaults} | Private];
+            Metas = head_and_definition_meta(Check, Meta, MaxDefaults - Defaults, All),
+            [{Tuple, Kind, Metas, MaxDefaults} | Private];
           false ->
             Private
         end,
@@ -92,6 +92,13 @@ fetch_definition([], _File, _Module, _Set, _Bag, All, Private) ->
 add_defaults_to_meta(0, Meta) -> Meta;
 add_defaults_to_meta(Defaults, Meta) -> [{defaults, Defaults} | Meta].
 
+head_and_definition_meta(true, Meta, 0, _All) ->
+  Meta;
+head_and_definition_meta(true, _Meta, _HeadDefaults, [{_, _, HeadMeta, _} | _]) ->
+  HeadMeta;
+head_and_definition_meta(false, _Meta, _HeadDefaults, _All) ->
+  false.
+
 %% Section for storing definitions
 
 store_definition(Kind, CheckClauses, Call, Body, Pos) ->
@@ -242,22 +249,23 @@ store_definition(Check, Kind, Meta, Name, Arity, File, Module, Defaults, Clauses
       ok
   end,
 
-  MaxDefaults =
+  {MaxDefaults, FirstMeta} =
     case ets:lookup(Set, {def, Tuple}) of
       [{_, StoredKind, StoredMeta, StoredFile, StoredCheck, {StoredDefaults, LastHasBody, LastDefaults}}] ->
         check_valid_kind(Meta, File, Name, Arity, Kind, StoredKind),
         (Check and StoredCheck) andalso
           check_valid_clause(Meta, File, Name, Arity, Kind, Set, StoredMeta, StoredFile),
         check_valid_defaults(Meta, File, Name, Arity, Kind, Defaults, StoredDefaults, LastDefaults, HasBody, LastHasBody),
-        max(Defaults, StoredDefaults);
+
+        {max(Defaults, StoredDefaults), StoredMeta};
       [] ->
         ets:insert(Bag, {defs, Tuple}),
-        Defaults
+        {Defaults, Meta}
     end,
 
   Check andalso ets:insert(Set, {?last_def, Tuple}),
   ets:insert(Bag, [{{clauses, Tuple}, Clause} || Clause <- Clauses]),
-  ets:insert(Set, {{def, Tuple}, Kind, Meta, File, Check, {MaxDefaults, HasBody, Defaults}}).
+  ets:insert(Set, {{def, Tuple}, Kind, FirstMeta, File, Check, {MaxDefaults, HasBody, Defaults}}).
 
 %% Handling of defaults
 
diff --git a/lib/elixir/test/elixir/kernel/warning_test.exs b/lib/elixir/test/elixir/kernel/warning_test.exs
index 76c986eb6..95f257718 100644
--- a/lib/elixir/test/elixir/kernel/warning_test.exs
+++ b/lib/elixir/test/elixir/kernel/warning_test.exs
@@ -343,7 +343,7 @@ defmodule Kernel.WarningTest do
                defp hello, do: nil
              end
              """)
-           end) =~ "function hello/0 is unused"
+           end) =~ "function hello/0 is unused\n  nofile:2"
 
     assert capture_err(fn ->
              Code.eval_string("""
@@ -352,7 +352,7 @@ defmodule Kernel.WarningTest do
                defp hello(1), do: :ok
              end
              """)
-           end) =~ "function hello/1 is unused"
+           end) =~ "function hello/1 is unused\n  nofile:2"
 
     assert capture_err(fn ->
              Code.eval_string(~S"""
@@ -363,20 +363,34 @@ defmodule Kernel.WarningTest do
                defp d(x), do: x
              end
              """)
-           end) =~ "function c/2 is unused"
-  after
-    purge([Sample1, Sample2, Sample3])
-  end
+           end) =~ "function c/2 is unused\n  nofile:4"
 
-  test "unused cyclic functions" do
     assert capture_err(fn ->
-             Code.eval_string("""
-             defmodule Sample do
-               defp a, do: b()
-               defp b, do: a()
+             Code.eval_string(~S"""
+             defmodule Sample4 do
+               def a, do: nil
+               defp b(x \\ 1, y \\ 1)
+               defp b(x, y), do: [x, y]
              end
              """)
-           end) =~ "function a/0 is unused"
+           end) =~ "function b/2 is unused\n  nofile:3"
+  after
+    purge([Sample1, Sample2, Sample3, Sample4])
+  end
+
+  test "unused cyclic functions" do
+    message =
+      capture_err(fn ->
+        Code.eval_string("""
+        defmodule Sample do
+          defp a, do: b()
+          defp b, do: a()
+        end
+        """)
+      end)
+
+    assert message =~ "function a/0 is unused\n  nofile:2"
+    assert message =~ "function b/0 is unused\n  nofile:3"
   after
     purge(Sample)
   end
@@ -418,7 +432,7 @@ defmodule Kernel.WarningTest do
                defp b(arg1 \\ 1, arg2 \\ 2, arg3 \\ 3), do: [arg1, arg2, arg3]
              end
              """)
-           end) =~ "default arguments in b/3 are never used"
+           end) =~ "default arguments in b/3 are never used\n  nofile:3"
 
     assert capture_err(fn ->
              Code.eval_string(~S"""
@@ -427,7 +441,7 @@ defmodule Kernel.WarningTest do
                defp b(arg1 \\ 1, arg2 \\ 2, arg3 \\ 3), do: [arg1, arg2, arg3]
              end
              """)
-           end) =~ "the first 2 default arguments in b/3 are never used"
+           end) =~ "the first 2 default arguments in b/3 are never used\n  nofile:3"
 
     assert capture_err(fn ->
              Code.eval_string(~S"""
@@ -436,7 +450,7 @@ defmodule Kernel.WarningTest do
                defp b(arg1 \\ 1, arg2 \\ 2, arg3 \\ 3), do: [arg1, arg2, arg3]
              end
              """)
-           end) =~ "the first default argument in b/3 is never used"
+           end) =~ "the first default argument in b/3 is never used\n  nofile:3"
 
     assert capture_err(fn ->
              Code.eval_string(~S"""
@@ -446,8 +460,30 @@ defmodule Kernel.WarningTest do
              end
              """)
            end) == ""
+
+    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 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 first 2 default arguments in b/3 are never used\n  nofile:3"
   after
-    purge([Sample1, Sample2, Sample3, Sample4])
+    purge([Sample1, Sample2, Sample3, Sample4, Sample5, Sample6])
   end
 
   test "unused import" do