core_lib: Handle patterns in map values

core_lib:is_var_used/2 would not consider a variable used in the
value of a map pattern such as:

  case Map of
    #{key := <<42:N>>} -> ok
  end

Here the variable 'N' would not be considered used.

It was assumed that there was no need to check map patterns at
all, since maps currently don't support variables in keys.

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/compiler/src/core_lib.erl b/lib/compiler/src/core_lib.erl
index 2792fd8fa5..0d95971f91 100644
--- a/lib/compiler/src/core_lib.erl
+++ b/lib/compiler/src/core_lib.erl
@@ -212,6 +212,8 @@ vu_pattern(V, #c_tuple{es=Es}, St) ->
     vu_pattern_list(V, Es, St);
 vu_pattern(V, #c_binary{segments=Ss}, St) ->
     vu_pat_seg_list(V, Ss, St);
+vu_pattern(V, #c_map{es=Es}, St) ->
+    vu_map_pairs(V, Es, St);
 vu_pattern(V, #c_alias{var=Var,pat=P}, St0) ->
     case vu_pattern(V, Var, St0) of
 	{true,_}=St1 -> St1;
@@ -234,6 +236,13 @@ vu_pat_seg_list(V, Ss, St) ->
 			end
 		end, St, Ss).
 
+vu_map_pairs(V, [#c_map_pair{val=Pat}|T], St0) ->
+    case vu_pattern(V, Pat, St0) of
+	{true,_}=St -> St;
+	St -> vu_map_pairs(V, T, St)
+    end;
+vu_map_pairs(_, [], St) -> St.
+
 -spec vu_var_list(cerl:var_name(), [cerl:c_var()]) -> boolean().
 
 vu_var_list(V, Vs) ->