From 1c39738beb152456b0540e6acb25812f97c7c4bd Mon Sep 17 00:00:00 2001
From: Taylan Kammer <taylan.kammer@gmail.com>
Date: Wed, 23 Sep 2026 16:42:42 +0200
Subject: New note.

---
 src/zisp/value.zig | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/zisp/value.zig b/src/zisp/value.zig
index aff05fe..413330c 100644
--- a/src/zisp/value.zig
+++ b/src/zisp/value.zig
@@ -75,8 +75,11 @@ pub const none  = Value{ .misc = .{ .value = .none  } };
 /// A plain (unpacked, untagged, uncompressed) pointer into the main heap.
 pub const HeapPtr = *align(16) anyopaque;
 
-/// Values for the 8 type bits on main heap pointers.
+/// Values for the 8 type bits on regular heap pointers.
 pub const HeapType = enum(u8) {
+    /// Special "invalid" tag, equals zero
+    _invalid,
+
     /// Pair (car, cdr)
     pair,
 
-- 
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