beam_validator: Support subtraction in update_container_type/4

weiss · Apr 27, 2021 · ba43dcc · ba43dcc
1 parent 1eb7ac2
commit ba43dcc
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Showing 2 changed files with 36 additions and 7 deletions.
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
@@ -2093,7 +2093,7 @@ update_type(Merge, With, #value_ref{}=Ref, Vst0) ->
         none ->
             throw({type_conflict, Current, With});
         Type ->
-            Vst = update_container_type(Type, Ref, Vst0),
+            Vst = update_container_type(Merge, With, Ref, Vst0),
             set_type(Type, Ref, Vst)
     end;
 update_type(Merge, With, {Kind,_}=Reg, Vst) when Kind =:= x; Kind =:= y ->
@@ -2108,13 +2108,19 @@ update_type(Merge, With, Literal, Vst) ->
     end.
 
 %% Updates the container the given value was extracted from, if any.
-update_container_type(Type, Ref, #vst{current=#st{vs=Vs}}=Vst) ->
+update_container_type(Merge, With, Ref, #vst{current=#st{vs=Vs}}=Vst) ->
     case Vs of
         #{ Ref := #value{op={bif,element},
                          args=[{integer,Index},Tuple]} } when Index >= 1 ->
-            Es = beam_types:set_tuple_element(Index, Type, #{}),
-            TupleType = #t_tuple{size=Index,elements=Es},
-            update_type(fun meet/2, TupleType, Tuple, Vst);
+            case beam_types:set_tuple_element(Index, With, #{}) of
+                #{ Index := _ }=Es ->
+                    TupleType = #t_tuple{size=Index,elements=Es},
+                    update_type(Merge, TupleType, Tuple, Vst);
+                #{} ->
+                    %% Index was above the element limit; subtract/2 won't be
+                    %% safe and meet/2 won't do anything.
+                    Vst
+            end;
         #{} ->
             Vst
     end.

diff --git a/lib/compiler/test/beam_type_SUITE.erl b/lib/compiler/test/beam_type_SUITE.erl
@@ -25,7 +25,11 @@
 	 cons/1,tuple/1,record_float/1,binary_float/1,float_compare/1,
 	 arity_checks/1,elixir_binaries/1,find_best/1,
          test_size/1,cover_lists_functions/1,list_append/1,bad_binary_unit/1,
-         none_argument/1,success_type_oscillation/1,type_subtraction/1]).
+         none_argument/1,success_type_oscillation/1,type_subtraction/1,
+         container_subtraction/1]).
+
+%% Force id/1 to return 'any'.
+-export([id/1]).
 
 suite() -> [{ct_hooks,[ts_install_cth]}].
 
@@ -53,7 +57,8 @@ groups() ->
        bad_binary_unit,
        none_argument,
        success_type_oscillation,
-       type_subtraction
+       type_subtraction,
+       container_subtraction
       ]}].
 
 init_per_suite(Config) ->
@@ -633,5 +638,23 @@ ts_23(_x@1) ->
             2
     end.
 
+%% GH-4774: The validator didn't update container contents on type subtraction.
+container_subtraction(Config) when is_list(Config) ->
+    A = id(baz),
+
+    cs_1({foo,[]}),
+    cs_1({bar,A}),
+    cs_2({bar,A}),
+
+    ok.
+
+cs_1({_,[]}) ->
+    ok;
+cs_1({_,_}=Other) ->
+    cs_2(Other).
+
+cs_2({bar,baz}) ->
+    ok.
+
 id(I) ->
     I.