Fix incorrect internal consistency failure for binary matching code

4c31fd0b9665 made the merging of match contexts stricter;
in fact, a little bit too strict.

Two match contexts with different number of slots would
be downgraded to the 'term' type. The correct way is to
keep the match context but set the number of slots to the
lowest number of slots of the two match contexts.

https://bugs.erlang.org/browse/ERL-490

1 files changed, 3 insertions, 3 deletions

diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index 00901077d3..be8908dd6b 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -1430,13 +1430,13 @@ merge_types(bool, {atom,A}) ->
     merge_bool(A);
 merge_types({atom,A}, bool) ->
     merge_bool(A);
-merge_types(#ms{id=Id1,valid=B0,slots=Slots},
-	    #ms{id=Id2,valid=B1,slots=Slots}) ->
+merge_types(#ms{id=Id1,valid=B1,slots=Slots1},
+	    #ms{id=Id2,valid=B2,slots=Slots2}) ->
     Id = if
              Id1 =:= Id2 -> Id1;
              true -> make_ref()
          end,
-    #ms{id=Id,valid=B0 band B1,slots=Slots};
+    #ms{id=Id,valid=B1 band B2,slots=min(Slots1, Slots2)};
 merge_types(T1, T2) when T1 =/= T2 ->
     %% Too different. All we know is that the type is a 'term'.
     term.