From 91f8245a0c90e7388bd4cc86a00314ca08c0636e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?fn=20=E2=8C=83=20=E2=8C=A5?=
 <70830482+FnControlOption@users.noreply.github.com>
Date: Mon, 24 Oct 2022 07:52:17 -0700
Subject: [PATCH] class.c (mrb_instance_alloc): raise error if
 NilClass/FalseClass.

MRB_TT_FALSE is equal to 0, so we have to explicitly check if the
class is either NilClass or FalseClass.
---
 src/class.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/class.c b/src/class.c
index 2b90db58b..dfec8c5eb 100644
--- a/src/class.c
+++ b/src/class.c
@@ -1939,7 +1939,12 @@ mrb_instance_alloc(mrb_state *mrb, mrb_value cv)
   if (c->tt == MRB_TT_SCLASS)
     mrb_raise(mrb, E_TYPE_ERROR, "can't create instance of singleton class");
 
-  if (ttype == 0) ttype = MRB_TT_OBJECT;
+  if (c == mrb->nil_class || c == mrb->false_class) {
+    mrb_assert(ttype == 0);
+  }
+  else if (ttype == 0) {
+    ttype = MRB_TT_OBJECT;
+  }
   if (ttype <= MRB_TT_CPTR) {
     mrb_raisef(mrb, E_TYPE_ERROR, "can't create instance of %v", cv);
   }