Fix expansion of map update arguments

Reported-by: José Valim

2 files changed, 13 insertions, 5 deletions

diff --git a/lib/compiler/src/sys_pre_expand.erl b/lib/compiler/src/sys_pre_expand.erl
index 9998043013..91a46a20fe 100644
--- a/lib/compiler/src/sys_pre_expand.erl
+++ b/lib/compiler/src/sys_pre_expand.erl
@@ -331,9 +331,10 @@ expr({tuple,Line,Es0}, St0) ->
 expr({map,Line,Es0}, St0) ->
     {Es1,St1} = expr_list(Es0, St0),
     {{map,Line,Es1},St1};
-expr({map,Line,Var,Es0}, St0) ->
-    {Es1,St1} = expr_list(Es0, St0),
-    {{map,Line,Var,Es1},St1};
+expr({map,Line,E0,Es0}, St0) ->
+    {E1,St1} = expr(E0, St0),
+    {Es1,St2} = expr_list(Es0, St1),
+    {{map,Line,E1,Es1},St2};
 expr({map_field_assoc,Line,K0,V0}, St0) ->
     {K,St1} = expr(K0, St0),
     {V,St2} = expr(V0, St1),
diff --git a/lib/compiler/test/map_SUITE.erl b/lib/compiler/test/map_SUITE.erl
index 7d35ffc8d5..3080f135b9 100644
--- a/lib/compiler/test/map_SUITE.erl
+++ b/lib/compiler/test/map_SUITE.erl
@@ -42,7 +42,8 @@
 	t_build_and_match_val/1,
 
 	%% errors in 17.0-rc1
-	t_update_values/1
+	t_update_values/1,
+        t_expand_map_update/1
     ]).
 
 suite() -> [].
@@ -68,7 +69,8 @@ all() -> [
 	t_build_and_match_val,
 
 	%% errors in 17.0-rc1
-	t_update_values
+	t_update_values,
+        t_expand_map_update
     ].
 
 groups() -> [].
@@ -273,6 +275,11 @@ t_update_values(Config) when is_list(Config) ->
 	end, {none, none, #{val1=>none,val2=>none}},List),
     ok.
 
+t_expand_map_update(Config) when is_list(Config) ->
+    M = #{<<"hello">> => <<"world">>}#{<<"hello">> := <<"les gens">>},
+    #{<<"hello">> := <<"les gens">>} = M,
+    ok.
+
 check_val(#{val1:=V1, val2:=V2},V1,V2) -> ok.
 
 get_val(#{ "wazzup" := _, val := V}) -> V;