introduce version switch, to make dialyzer rather happy

rebar.config.script

@@ -0,0 +1,17 @@
+case erlang:system_info(otp_release) of
+
+    [$R|_] ->
+        %% Rxx < 17.0, not border inclusive
+        HashDefine = [{d,pre17}],
+        case lists:keysearch(erl_opts, 1, CONFIG) of
+            {value, {erl_opts, Opts}} ->
+                lists:keyreplace(erl_opts,1,CONFIG,{erl_opts,Opts++HashDefine});
+            false ->
+                CONFIG ++ [{erl_opts, HashDefine}]
+        end;
+
+    _ ->
+        %% "17", our future with map
+        CONFIG
+
+end.

src/riak_pb_kv_codec.erl

@@ -49,7 +49,13 @@
 -type quorum() :: symbolic_quorum() | non_neg_integer().
 -type symbolic_quorum() :: one | quorum | all | default.
 -type value() :: binary().
+
+-ifdef(pre17).
+-type metadata() :: dict().
+-else.
 -type metadata() :: dict:dict(binary(), binary()).
+-endif.
+
 -type contents() :: [{metadata(), value()}].
 
 %% @doc Convert a list of object {MetaData,Value} pairs to protocol