Inspect ill-formed structs as maps

lib/elixir/lib/inspect.ex

@@ -475,6 +475,32 @@ defimpl Inspect, for: Map do
     map_container_doc(infos, name, opts, fun)
   end
 
+  def valid_struct?(struct) do
+    !!valid_struct_info(struct)
+  end
+
+  def valid_struct_info(%module{} = struct) do
+    try do
+      module.__info__(:struct)
+    rescue
+      _ -> nil
+    else
+      info ->
+        if valid_struct?(info, struct, map_size(struct) - 1) do
+          info
+        end
+    end
+  end
+
+  defp valid_struct?([%{field: field} | info], struct, count) when is_map_key(struct, field),
+    do: valid_struct?(info, struct, count - 1)
+
+  defp valid_struct?([], _struct, 0),
+    do: true
+
+  defp valid_struct?(_fields, _struct, _count),
+    do: false
+
   defp to_assoc({key, value}, opts, sep) do
     {key_doc, opts} = to_doc_with_opts(key, opts)
     {value_doc, opts} = to_doc_with_opts(value, opts)
@@ -662,36 +688,18 @@ end
 
 defimpl Inspect, for: Any do
   def inspect(%module{} = struct, opts) do
-    try do
-      module.__info__(:struct)
-    rescue
-      _ -> Inspect.Map.inspect_as_map(struct, opts)
-    else
-      info ->
-        if valid_struct?(info, struct) do
-          info =
-            for %{field: field} = map <- info,
-                field != :__exception__,
-                do: map
+    if info = Inspect.Map.valid_struct_info(struct) do
+      info =
+        for %{field: field} = map <- info,
+            field != :__exception__,
+            do: map
 
-          Inspect.Map.inspect_as_struct(struct, Macro.inspect_atom(:literal, module), info, opts)
-        else
-          Inspect.Map.inspect_as_map(struct, opts)
-        end
+      Inspect.Map.inspect_as_struct(struct, Macro.inspect_atom(:literal, module), info, opts)
+    else
+      Inspect.Map.inspect_as_map(struct, opts)
     end
   end
 
-  defp valid_struct?(info, struct), do: valid_struct?(info, struct, map_size(struct) - 1)
-
-  defp valid_struct?([%{field: field} | info], struct, count) when is_map_key(struct, field),
-    do: valid_struct?(info, struct, count - 1)
-
-  defp valid_struct?([], _struct, 0),
-    do: true
-
-  defp valid_struct?(_fields, _struct, _count),
-    do: false
-
   def inspect_as_struct(map, name, infos, opts) do
     open = color_doc("#" <> name <> "<", :map, opts)
     sep = color_doc(",", :map, opts)

lib/elixir/lib/inspect/algebra.ex

@@ -396,7 +396,7 @@ defmodule Inspect.Algebra do
   def to_doc_with_opts(term, opts)
 
   def to_doc_with_opts(%_{} = struct, %Inspect.Opts{inspect_fun: fun} = opts) do
-    if opts.structs do
+    if opts.structs and Inspect.Map.valid_struct?(struct) do
       try do
         fun.(struct, opts)
       rescue

lib/elixir/test/elixir/calendar/date_range_test.exs

@@ -149,27 +149,6 @@ defmodule Date.RangeTest do
   end
 
   describe "old date ranges" do
-    test "inspect" do
-      asc = %{
-        __struct__: Date.Range,
-        first: ~D[2021-07-14],
-        first_in_iso_days: 738_350,
-        last: ~D[2021-07-17],
-        last_in_iso_days: 738_353
-      }
-
-      desc = %{
-        __struct__: Date.Range,
-        first: ~D[2021-07-17],
-        first_in_iso_days: 738_353,
-        last: ~D[2021-07-14],
-        last_in_iso_days: 738_350
-      }
-
-      assert inspect(asc) == "Date.range(~D[2021-07-14], ~D[2021-07-17])"
-      assert inspect(desc) == "Date.range(~D[2021-07-17], ~D[2021-07-14], -1)"
-    end
-
     test "enumerable" do
       asc = %{
         __struct__: Date.Range,

lib/elixir/test/elixir/inspect_test.exs

@@ -445,6 +445,13 @@ defmodule Inspect.MapTest do
              "%{__struct__: Inspect.MapTest.Public, foo: :bar, key: 1}"
   end
 
+  test "public modified struct with defimpl" do
+    map_set = MapSet.new([1, 2])
+
+    assert inspect(Map.put(map_set, :foo, :bar), custom_options: [sort_maps: true]) ==
+             "%{__struct__: MapSet, foo: :bar, map: %{1 => [], 2 => []}}"
+  end
+
   test "private struct" do
     assert inspect(%{__struct__: Private, key: 1}, custom_options: [sort_maps: true]) ==
              "%{__struct__: Inspect.MapTest.Private, key: 1}"

lib/elixir/test/elixir/range_test.exs

@@ -200,14 +200,6 @@ defmodule RangeTest do
   end
 
   describe "old ranges" do
-    test "inspect" do
-      asc = %{__struct__: Range, first: 1, last: 3}
-      desc = %{__struct__: Range, first: 3, last: 1}
-
-      assert inspect(asc) == "1..3"
-      assert inspect(desc) == "3..1//-1"
-    end
-
     test "enum" do
       asc = %{__struct__: Range, first: 1, last: 3}
       desc = %{__struct__: Range, first: 3, last: 1}