Merge pull request #8101 from jhogberg/john/fix-another-0.0-issue/GH-…

…8097

beam_types: Fix another +0.0/-0.0 issue

lib/compiler/src/beam_types.erl

@@ -260,10 +260,15 @@ join(#t_tuple{}=A, #t_tuple{}=B) ->
             lub(A, B);
         {_Key, none} ->
             lub(A, B);
-        {KeyA, KeyB} when KeyA < KeyB ->
-            #t_union{tuple_set=[{KeyA, A}, {KeyB, B}]};
-        {KeyA, KeyB} when KeyA > KeyB ->
-            #t_union{tuple_set=[{KeyB, B}, {KeyA, A}]}
+        {KeyA, KeyB} ->
+            %% We must use total ordering rather than plain '<' as -0.0 differs
+            %% from +0.0
+            case total_compare(KeyA, KeyB, fun erlang:'<'/2) of
+                true ->
+                    #t_union{tuple_set=[{KeyA, A}, {KeyB, B}]};
+                false ->
+                    #t_union{tuple_set=[{KeyB, B}, {KeyA, A}]}
+            end
     end;
 join(#t_tuple{}=A, B) ->
     %% All other combinations have been tried already, so B must be 'other'

lib/compiler/test/beam_type_SUITE.erl

@@ -1514,6 +1514,7 @@ float_confusion(_Config) ->
     {'EXIT', _} = catch float_confusion_3(id(0.0)),
     ok = float_confusion_4(id(1)),
     {'EXIT', _} = catch float_confusion_5(),
+    {'EXIT', _} = catch float_confusion_6(),
     ok.
 
 float_confusion_1(_, _) ->
@@ -1547,6 +1548,22 @@ float_confusion_5() ->
         end * 0,
     ok.
 
+%% GH-8097: Record keys weren't compared in total order, confusing +0.0 and
+%% -0.0 and crashing the compiler.
+float_confusion_6() ->
+    <<
+        (ok)
+     || _ := {_V1} <- ok,
+        (maybe
+            {} ?= _V1
+        else
+            -0.0 ->
+                [];
+            0.0 ->
+                []
+        end)
+    >>.
+
 %%%
 %%% Common utilities.
 %%%