check quantites of subject and global

- subj qty must be 0 or 1 (atkey)
- global must not be 0 if used at non-0

src/Quox/Syntax/Qty.idr

@@ -70,3 +70,14 @@ IsQty Qty where
   zero  = Zero; one = One
   (+)   = plus; (*) = times
   (<=.) = compat
+
+
+public export
+data IsSubj : Qty -> Type where
+  SZero : IsSubj Zero
+  SOne  : IsSubj One
+
+public export
+data IsGlobal : Qty -> Type where
+  GZero : IsGlobal Zero
+  GAny  : IsGlobal Any