From a1be8cbc141b00c3433e85a290b4c69682c4979e Mon Sep 17 00:00:00 2001
From: Jarvis Carroll <spiveehere@gmail.com>
Date: Tue, 23 Sep 2025 19:22:30 +1000
Subject: [PATCH] coerce hashes

It turns out there are a lot of types that, like option, should only be
valid as an opaque/normalized type, but should be substituted for
something different in the flat representation. If we restructure things
a little then we can implement all of these in one go.
---
 src/hz.erl | 36 ++++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/src/hz.erl b/src/hz.erl
index 5d0b2f8..b48b891 100644
--- a/src/hz.erl
+++ b/src/hz.erl
@@ -1658,6 +1658,12 @@ normalize_opaque_type(T, Types) ->
         true  -> {ok, true, T, T}
     end.
 
+% This function evaluates type aliases in a loop, until eventually a usable
+% definition is found.
+%
+% It also evaluates built-in and standard library types such as options and
+% names, to their defined variant representation, as well as evaluating
+% certain binary types like hash, fp, and fr, into their byte representations.
 % FIXME detect infinite loops
 % FIXME detect builtins with the wrong number of arguments
 % FIXME should nullary types have an empty list of arguments added before now?
@@ -1665,6 +1671,10 @@ normalize_opaque_type({option, [T]}, _Types, IsFirst) ->
     % Just like user-made ADTs, 'option' is considered part of the type, and so
     % options are considered normalised.
     {ok, IsFirst, {option, [T]}, {variant, [{"None", []}, {"Some", [T]}]}};
+normalize_opaque_type(hash, _Types, IsFirst) ->
+    % For coercion purposes, hash is indistinguishable from bytes(32), so we
+    % treat it like a type alias.
+    {ok, IsFirst, hash, {bytes, [32]}};
 normalize_opaque_type(T, Types, IsFirst) when is_list(T) ->
     normalize_opaque_type({T, []}, Types, IsFirst);
 normalize_opaque_type({T, TypeArgs}, Types, IsFirst) when is_list(T) ->
@@ -1709,7 +1719,10 @@ normalize_opaque_type3(NextT, Types) ->
 
 % Strings indicate names that should be substituted. Atoms indicate built in
 % types, which don't need to be expanded, except for option.
+% TODO: Stop calling this, so that we can stop redundantly enumerating all the
+% built in types.
 type_is_expanded({option, _})            -> false;
+type_is_expanded(hash)                   -> false;
 type_is_expanded(X) when is_atom(X)      -> true;
 type_is_expanded({X, _}) when is_atom(X) -> true;
 type_is_expanded(_)                      -> false.
@@ -2578,6 +2591,13 @@ coerce_unicode_test() ->
     {ok, $ḉ} = coerce(Type, <<"ḉ"/utf8>>, to_fate),
     ok.
 
+coerce_hash_test() ->
+    {ok, Type} = annotate_type(hash, #{}),
+    Hash = list_to_binary(lists:seq(1,32)),
+    try_coerce(Type, Hash, Hash),
+    ok.
+
+
 
 %%% Complex AACI paramter and namespace tests
 
@@ -2674,20 +2694,20 @@ obscure_aaci_test() ->
             entrypoint any_bytes(): bytes() = Bytes.to_any_size(#112233)
             entrypoint bits(): bits = Bits.all
             entrypoint character(): char = 'a'
+            entrypoint hash(): hash = #00112233445566778899AABBCCDDEEFF00112233445566778899AABBCCDDEEFF
     ",
     {ok, AACI} = aaci_from_string(Contract),
 
-    IntAnnotated = {integer, already_normalized, integer},
-    OptionFlat = {variant, [{"None", []}, {"Some", [IntAnnotated]}]},
-    OptionAnnotated = {{option, [integer]}, already_normalized, OptionFlat},
-    {ok, {[], OptionAnnotated}} = aaci_lookup_spec(AACI, "options"),
+    {ok, {[], {{option, [integer]}, _, _}}} = aaci_lookup_spec(AACI, "options"),
 
-    {ok, {[], {_, _, {bytes, [4]}}}} = aaci_lookup_spec(AACI, "fixed_bytes"),
-    {ok, {[], {_, _, {bytes, [any]}}}} = aaci_lookup_spec(AACI, "any_bytes"),
+    {ok, {[], {{bytes, [4]}, _, _}}} = aaci_lookup_spec(AACI, "fixed_bytes"),
+    {ok, {[], {{bytes, [any]}, _, _}}} = aaci_lookup_spec(AACI, "any_bytes"),
 
-    {ok, {[], {_, _, bits}}} = aaci_lookup_spec(AACI, "bits"),
+    {ok, {[], {bits, _, _}}} = aaci_lookup_spec(AACI, "bits"),
 
-    {ok, {[], {_, _, char}}} = aaci_lookup_spec(AACI, "character"),
+    {ok, {[], {char, _, _}}} = aaci_lookup_spec(AACI, "character"),
+
+    {ok, {[], {hash, _, _}}} = aaci_lookup_spec(AACI, "hash"),
 
     ok.