From c4a08f333e127c8d8af83c608cf8bcb6d01b7871 Mon Sep 17 00:00:00 2001
From: Ralf Jung <jung@mpi-sws.org>
Date: Fri, 22 Nov 2019 17:20:03 +0100
Subject: [PATCH] expand not on structural cell

---
 Missing.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Missing.md b/Missing.md
index b43c0db5..76971ab8 100644
--- a/Missing.md
+++ b/Missing.md
@@ -5,6 +5,8 @@ Missing APIs from the types we cover (APIs have been added after this formalizat
 * Structural conversion for slices.  The matching operations in our model would be
   `&mut Cell<(A, B)>` -> `&mut (Cell<A>, Cell<B>)` and
   `&Cell<(A, B)>` -> `&(Cell<A>, Cell<B>)` (both being NOPs).
+  * Turns out to be very hard!  The way we currently associate NA-masks with locations is in conflict with this.
+    The invariant for the entire cell gets allocated "on" the first location of the cell, so when we do splitting the 2nd projection has no way to access it...
 
 # ZST
 
-- 
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