doc/concepts.tex: Add cross-ref to conversions in slot-access description.

diff --git a/doc/concepts.tex b/doc/concepts.tex
index 21951dd..405cad1 100644 (file)
--- a/doc/concepts.tex
+++ b/doc/concepts.tex
@@ -370,6 +370,11 @@ to it in a slot.  (This will also help preserve binary compatibility, because
 the private structure can grow more members as needed.  See
 \xref{sec:concepts.compatibility} for more details.)
 
+Slots defined by $C$'s link superclass, or any other superclass in the same
+chain, can be accessed in the same way.  Slots defined by other superclasses
+can't be accessed directly: the instance pointer must be \emph{converted} to
+point to a different chain.  See the subsection `Conversions' below.
+
 
 \subsubsection{Sending messages}
 Sod defines a macro for each message.  If a class $C$ defines a message $m$,