Properly handle eval_failure warnings, closes #2835

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

Author: José Valim

lib/elixir/src/elixir_errors.erl

@@ -140,6 +140,11 @@ handle_file_warning(_, File, {Line,erl_lint,{unused_var,Var}}) ->
   Message = format_error(erl_lint, {unused_var, format_var(Var)}),
   warn(Line, File, Message);
 
+%% Handle literal eval failures
+handle_file_warning(_, File, {Line,sys_core_fold,{eval_failure, Error}}) ->
+  #{'__struct__' := Struct} = 'Elixir.Exception':normalize(error, Error),
+  warn(Line, File, ["this expression will fail with ", elixir_aliases:inspect(Struct)]);
+
 %% Default behaviour
 handle_file_warning(_, File, {Line,Module,Desc}) ->
   Message = format_error(Module, Desc),

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

@@ -375,6 +375,20 @@ defmodule Kernel.WarningTest do
     purge Sample
   end
 
+  test :badarg_warning do
+    assert capture_err(fn ->
+      assert_raise ArgumentError, fn ->
+        Code.eval_string """
+        defmodule Sample do
+          Atom.to_string "abc"
+        end
+        """
+      end
+    end) =~ "warning: this expression will fail with ArgumentError"
+  after
+    purge [Sample]
+  end
+
   test :undefined_function_for_behaviour do
     assert capture_err(fn ->
       Code.eval_string """