--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/druntime/src/compiler/dmd/invariant.d	Tue Nov 11 01:52:37 2008 +0100
@@ -0,0 +1,24 @@
+/*
+ * Placed into the Public Domain
+ * written by Walter Bright
+ * www.digitalmars.com
+ */
+
+void _d_invariant(Object o)
+{   ClassInfo c;
+
+    //printf("__d_invariant(%p)\n", o);
+
+    // BUG: needs to be filename/line of caller, not library routine
+    assert(o !is null); // just do null check, not invariant check
+
+    c = o.classinfo;
+    do
+    {
+        if (c.classInvariant)
+        {
+            (*c.classInvariant)(o);
+        }
+        c = c.base;
+    } while (c);
+}