3 files changed, 28 insertions, 9 deletions
diff --git a/src/ast_util.ml b/src/ast_util.ml
index 61bc9ba3..f0b6508b 100644
--- a/src/ast_util.ml
+++ b/src/ast_util.ml
@@ -888,6 +888,13 @@ let id_of_type_def (TD_aux (td_aux, _)) = id_of_type_def_aux td_aux
 
 let id_of_val_spec (VS_aux (VS_val_spec (_, id, _, _), _)) = id
 
+let id_of_dec_spec (DEC_aux (ds_aux, _)) =
+  match ds_aux with
+  | DEC_reg (_, id) -> id
+  | DEC_config (id, _, _) -> id
+  | DEC_alias (id, _) -> id
+  | DEC_typ_alias (_, id, _) -> id
+
 let ids_of_def = function
   | DEF_kind (KD_aux (KD_nabbrev (_, id, _, _), _)) -> IdSet.singleton id
   | DEF_type td -> IdSet.singleton (id_of_type_def td)
diff --git a/src/ast_util.mli b/src/ast_util.mli
index f55cdf16..2a303475 100644
--- a/src/ast_util.mli
+++ b/src/ast_util.mli
@@ -232,6 +232,7 @@ val string_of_index_range : index_range -> string
 val id_of_fundef : 'a fundef -> id
 val id_of_type_def : 'a type_def -> id
 val id_of_val_spec : 'a val_spec -> id
+val id_of_dec_spec : 'a dec_spec -> id
 
 val id_of_kid : kid -> id
 val kid_of_id : id -> kid
diff --git a/src/spec_analysis.ml b/src/spec_analysis.ml
index 75f55c9c..c858754e 100644
--- a/src/spec_analysis.ml
+++ b/src/spec_analysis.ml
@@ -447,15 +447,26 @@ let rec fv_of_scattered consider_var consider_scatter_as_one all_defs (SD_aux(sd
       else init_env name in
     init_env (name ^ "/end"), uses
 
-let fv_of_rd consider_var (DEC_aux (d,_)) = match d with
-  | DEC_reg(t,id) ->
-    init_env (string_of_id id), fv_of_typ consider_var mt mt t
-  | DEC_config(id,t,exp) ->
-    init_env (string_of_id id), fv_of_typ consider_var mt mt t
-  | DEC_alias(id,alias) ->
-    init_env (string_of_id id),mt
-  | DEC_typ_alias(t,id,alias) ->
-    init_env (string_of_id id), mt
+let fv_of_rd consider_var (DEC_aux (d, annot)) =
+  (* When we get the free variables of a register, we have to ensure
+     that we expand all synonyms so we can pick up dependencies with
+     undefined_type function, even when type is indirected through a
+     synonym. *)
+  let open Type_check in
+  let env = env_of_annot annot in
+  match d with
+  | DEC_reg(t, id) ->
+     let t' = Env.expand_synonyms env t in
+     init_env (string_of_id id),
+     Nameset.union (fv_of_typ consider_var mt mt t) (fv_of_typ consider_var mt mt t')
+  | DEC_config(id, t, exp) ->
+     let t' = Env.expand_synonyms env t in
+     init_env (string_of_id id),
+     Nameset.union (fv_of_typ consider_var mt mt t) (fv_of_typ consider_var mt mt t')
+  | DEC_alias(id, alias) ->
+     init_env (string_of_id id), mt
+  | DEC_typ_alias(t, id, alias) ->
+     init_env (string_of_id id), mt
 
 let fv_of_def consider_var consider_scatter_as_one all_defs = function
   | DEF_kind kdef -> fv_of_kind_def consider_var kdef