From 7eb29827a61f5228063d6347b9703ac95cb854fd Mon Sep 17 00:00:00 2001
From: SpiveeWorks <spiveehere@gmail.com>
Date: Fri, 24 Jan 2025 18:50:41 +1100
Subject: [PATCH] Fix type substitution into variants and records

Variants were working by accident, since
{variant, [{"VariantName", [Element]}]} had a similar enough form to
the opaque types that would come from something like
`type1(type2(int))`, but records were not working, since they have a
different form. Now both are handled explicitly so that only the
intended forms of each are handled.
---
 src/hz.erl | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/hz.erl b/src/hz.erl
index 7143e30..55fb64c 100644
--- a/src/hz.erl
+++ b/src/hz.erl
@@ -1662,12 +1662,39 @@ substitute_opaque_type(Bindings, {var, VarName}) ->
         false        -> {error, invalid_aci};
         {_, TypeArg} -> {ok, TypeArg}
     end;
+substitute_opaque_type(Bindings, {variant, Args}) ->
+    case substitute_variant_types(Bindings, Args, []) of
+        {ok, Result} -> {ok, {variant, Result}};
+        Error        -> Error
+    end;
+substitute_opaque_type(Bindings, {record, Args}) ->
+    case substitute_record_types(Bindings, Args, []) of
+        {ok, Result} -> {ok, {record, Result}};
+        Error        -> Error
+    end;
 substitute_opaque_type(Bindings, {Connective, Args}) ->
     case substitute_opaque_types(Bindings, Args, []) of
         {ok, Result} -> {ok, {Connective, Result}};
         Error        -> Error
     end;
-substitute_opaque_type(_Bindings, Type) -> {ok, Type}.
+substitute_opaque_type(_Bindings, Type) ->
+    {ok, Type}.
+
+substitute_variant_types(Bindings, [{VariantName, Elements} | Rest], Acc) ->
+    case substitute_opaque_types(Bindings, Elements, []) of
+        {ok, Result} -> substitute_variant_types(Bindings, Rest, [{VariantName, Result} | Acc]);
+        Error        -> Error
+    end;
+substitute_variant_types(_Bindings, [], Acc) ->
+    {ok, lists:reverse(Acc)}.
+
+substitute_record_types(Bindings, [{ElementName, Type} | Rest], Acc) ->
+    case substitute_opaque_type(Bindings, Type) of
+        {ok, Result} -> substitute_record_types(Bindings, Rest, [{ElementName, Result} | Acc]);
+        Error        -> Error
+    end;
+substitute_record_types(_Bindings, [], Acc) ->
+    {ok, lists:reverse(Acc)}.
 
 substitute_opaque_types(Bindings, [Next | Rest], Acc) ->
     case substitute_opaque_type(Bindings, Next) of