Insure bools remain 0x1 or 0x0 by having boolean-NOT not just be a simple bit-NOT.

src/Makefile

@@ -440,6 +440,7 @@ TEST_XFAILS_LLVM := $(TASK_XFAILS) \
                       bind-thunk.rs \
                       bind-trivial.rs \
                       bitwise.rs \
+                      bool-not.rs \
                       box-in-tup.rs \
                       box-unbox.rs \
                       cast.rs \

src/boot/me/trans.ml

@@ -2058,7 +2058,10 @@ let trans_visitor
             in
               anno ();
               emit (Il.unary op dst src);
-              Il.Cell dst
+              (* Insist the bool domain being 0x0 and 0x1 *)
+              if unop = Ast.UNOP_not
+              then trans_binary Ast.BINOP_and (Il.Cell dst) one
+              else Il.Cell dst
 
         | Ast.EXPR_atom a ->
             trans_atom a

src/test/run-pass/bool-not.rs

@@ -0,0 +1,15 @@
+// -*- rust -*-
+
+fn main() {
+  if (!false) {
+    check (true);
+  } else {
+    check (false);
+  }
+
+  if (!true) {
+    check (false);
+  } else {
+    check (true);
+  }
+}