Update all specifications when constant folding.

It used to only update IsExprs, but that meant that all the constants inside
types in other things didn't get folded properly, which caused problems.

frontends/OccamPasses.hs

@@ -79,13 +79,13 @@ foldConstants = applyDepthM2 doExpression doSpecification
         =  do (e', _, _) <- constantFold e
               return e'
 
-    -- When an expression is abbreviated, update its definition so that it can
-    -- be used when folding later expressions.
+    -- After we're done folding a specification, update its definition.
+    -- (Even if it isn't an expression itself, it might have others inside it,
+    -- so we just update them all.)
     doSpecification :: A.Specification -> PassM A.Specification
-    doSpecification s@(A.Specification _ n st@(A.IsExpr _ _ _ _))
+    doSpecification s@(A.Specification _ n st)
         =  do modifyName n (\nd -> nd { A.ndType = st })
               return s
-    doSpecification s = return s
 
 -- | Check that things that must be constant are.
 checkConstants :: Data t => t -> PassM t

testcases/const-array-dim.occ

@@ -0,0 +1,18 @@
+VAL INT screen.width IS 80:
+VAL INT screen.height IS 24:
+
+PROC clear.buffer ([screen.height][screen.width]BYTE screen, [screen.height][screen.width]INT colour)
+  SKIP
+:
+
+PROC screen.buffer (CHAN OF BYTE in, CHAN OF BYTE out)
+  [2][screen.height][screen.width]BYTE screen:
+  [2][screen.height][screen.width]INT colour:
+  SEQ
+    clear.buffer (screen[0], colour[0])
+    clear.buffer (screen[1], colour[1])
+:
+
+PROC q7 ()
+  SKIP
+: