Index: mozilla/xpcom/typelib/xpidl/xpidl_util.c
===================================================================
RCS file: /cvsroot/mozilla/xpcom/typelib/xpidl/xpidl_util.c,v
retrieving revision 1.21
diff -u -r1.21 mozilla/xpcom/typelib/xpidl/xpidl_util.c
--- mozilla/xpcom/typelib/xpidl/xpidl_util.c
+++ mozilla/xpcom/typelib/xpidl/xpidl_util.c
@@ -251,6 +251,42 @@
 }
 
 gboolean
+matches_IFoo(const char* substring)
+{
+    char letter = *substring;
+    if (letter != 'I')
+        return FALSE;
+    substring++; 
+    letter = *substring;
+    if (letter < 'A' ||
+        letter > 'Z')
+        return FALSE;
+    substring++;
+    letter = *substring;
+    if (letter < 'a' ||
+        letter > 'z')
+        return FALSE;
+    return TRUE;
+}
+
+gboolean
+matches_nsIFoo(const char* attribute_name)
+{
+    if (attribute_name[0] < 'a' ||
+        attribute_name[0] > 'z')
+        return FALSE;
+    if (attribute_name[1] < 'a' ||
+        attribute_name[1] > 'z')
+        return FALSE;
+    if (matches_IFoo(attribute_name+2))
+        return TRUE;
+    if (attribute_name[1] < 'a' ||
+        attribute_name[1] > 'z')
+        return FALSE;
+    return matches_IFoo(attribute_name+3);
+}
+
+gboolean
 verify_attribute_declaration(IDL_tree attr_tree)
 {
     IDL_tree iface;
@@ -344,6 +380,18 @@
             return FALSE;
         }
 
+        /*
+         * canIGoHomeNow is a bad name for an attribute.
+         * /^[a-z]{2,3}I[A-Z][a-z]/ => bad, reserved for
+         * interface flattening.
+         */
+        if (matches_nsIFoo(IDL_IDENT(IDL_LIST(IDL_ATTR_DCL(attr_tree).
+                simple_declarations).data).str)) {
+            XPIDL_WARNING((attr_tree, IDL_WARNING1,
+                 "Naming an attribute nsIFoo causes "
+                 "problems for interface flattening"));
+        }
+
         /* 
          * Run additional error checks on the attribute type if targetting an 
          * older version of XPConnect.