From ae9b8f8b163fa6c3f1ddcb5971c6c3d610a73683 Mon Sep 17 00:00:00 2001
From: Gaith Hallak <gaithhallak@gmail.com>
Date: Thu, 24 Feb 2022 16:03:47 +0400
Subject: [PATCH] Make is_subtype/4 a separate function

---
 src/aeso_ast_infer_types.erl | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/aeso_ast_infer_types.erl b/src/aeso_ast_infer_types.erl
index 2f0e32d..062affa 100644
--- a/src/aeso_ast_infer_types.erl
+++ b/src/aeso_ast_infer_types.erl
@@ -2747,16 +2747,9 @@ unify1(_Env, X, X, _Variance, _When) ->
 unify1(_Env, {id, _, Name}, {id, _, Name}, _Variance, _When) ->
     true;
 unify1(Env, A = {con, _, NameA}, B = {con, _, NameB}, Variance, When) ->
-    IsSubtype = case Variance of
-                    invariant     -> NameA == NameB;
-                    covariant     -> is_subtype(Env, NameA, NameB);
-                    contravariant -> is_subtype(Env, NameB, NameA);
-                    bivariant     -> is_subtype(Env, NameA, NameB)
-                end,
-    if
-        IsSubtype ->
-            true;
-        true ->
+    case is_subtype(Env, NameA, NameB, Variance) of
+        true -> true;
+        false ->
             cannot_unify(A, B, When),
             false
     end;
@@ -2803,6 +2796,15 @@ unify1(_Env, A, B, _Variance, When) ->
     cannot_unify(A, B, When),
     false.
 
+is_subtype(Env, NameA, NameB, invariant) ->
+    NameA == NameB;
+is_subtype(Env, NameA, NameB, covariant) ->
+    is_subtype(Env, NameA, NameB);
+is_subtype(Env, NameA, NameB, contravariant) ->
+    is_subtype(Env, NameB, NameA);
+is_subtype(Env, NameA, NameB, bivariant) ->
+    is_subtype(Env, NameA, NameB) orelse is_subtype(Env, NameB, NameA).
+
 is_subtype(Env, Child, Base) ->
     Parents = maps:get(Child, Env#env.contract_parents, []),
     if