Print warning when inspect fails

Author: José Valim

lib/elixir/lib/inspect/algebra.ex

@@ -110,8 +110,12 @@ defmodule Inspect.Algebra do
       if elem(opts, Inspect.Opts.__record__(:index, :records)) do
         try do
           Inspect.inspect(arg, opts)
-        catch
-          _, _ -> Inspect.Tuple.inspect(arg, opts)
+        rescue
+          e ->
+            res = Inspect.Tuple.inspect(arg, opts)
+            IO.puts :stderr, "** (Inspect.Error) Got #{inspect e.__record__(:name)} with message " <>
+                             "#{e.message} while inspecting #{pretty(res, opts.width)}"
+            res
         end
       else
         Inspect.Tuple.inspect(arg, opts)

lib/elixir/test/elixir/inspect_test.exs

@@ -156,20 +156,20 @@ defmodule Inspect.TupleTest do
     assert inspect(RuntimeError.new) == "RuntimeError[message: \"runtime error\"]"
   end
 
-  defrecord :something, [:a, :b]
-
-  test :non_module_record do
-    # They are on purpose not treated as Elixir records
-    # otherwise it affects inspect performance very strongly
-    assert inspect(:something.new) == "{:something, nil, nil}"
-  end
-
   defrecord Rec, value: 1
 
   test :two_items_record do
     assert inspect({ Rec[value: 1], 1 }) == "{Inspect.TupleTest.Rec[value: 1], 1}"
   end
 
+  test :false_positives do
+    import ExUnit.CaptureIO
+
+    assert capture_io(:stderr, fn ->
+      assert inspect({ Range, nil }) == "{Range, nil}"
+    end) =~ "** (Inspect.Error) Got FunctionClauseError with message no function clause matching in Inspect.Range.inspect/2"
+  end
+
   test :empty do
     assert inspect({}) == "{}"
   end

lib/elixir/test/elixir/range_test.exs

@@ -45,7 +45,6 @@ defmodule RangeTest do
   test :inspect do
     assert inspect(1..3) == "1..3"
     assert inspect(3..1) == "3..1"
-    assert inspect({ Range, nil }) == "{Range, nil}"
   end
 
   defp not_range do