style: factor the access to a rule from its items

* src/counterexample.c (item_rule): Move to...
* src/counterexample.h: here.
* src/AnnotationList.c, src/counterexample.c, src/ielr.c: Use it.

src/AnnotationList.c

@@ -185,7 +185,7 @@ AnnotationList__compute_conflicted_tokens (bitset shift_tokens,
 }
 
 static bool
-AnnotationList__compute_lhs_contributions (state *s, rule *the_rule,
+AnnotationList__compute_lhs_contributions (state *s, const rule *the_rule,
                                            symbol_number conflicted_token,
                                            bitsetv follow_kernel_items,
                                            bitsetv always_follows,
@@ -263,18 +263,12 @@ AnnotationList__computePredecessorAnnotations (
                 /* If this kernel item is next to the beginning of the RHS,
                    then check all of the predecessor's goto follows for the
                    LHS.  */
-                if (item_number_is_rule_number (ritem[s->items[self_item]
-                                                      - 2]))
+                if (item_number_is_rule_number (ritem[s->items[self_item] - 2]))
                   {
-                    int rulei;
-                    for (rulei = s->items[self_item];
-                         !item_number_is_rule_number (ritem[rulei]);
-                         ++rulei)
-                      continue;
                     Sbitset items;
                     if (AnnotationList__compute_lhs_contributions (
                           *predecessor,
-                          &rules[item_number_as_rule_number (ritem[rulei])],
+                          item_rule (&ritem[s->items[self_item]]),
                           contribution_token,
                           follow_kernel_items, always_follows, predecessors,
                           item_lookahead_sets, &items, annotations_obstackp))

src/counterexample.c

@@ -364,7 +364,7 @@ complete_diverging_example (symbol_number conflict_sym,
               lookahead_required = false;
             }
         }
-      rule_number r = item_number_as_rule_number (*i);
+      const rule *r = &rules[item_number_as_rule_number (*i)];
       // add derivations for symbols before dot
       for (i = item - 1; !item_number_is_rule_number (*i) && i >= ritem; i--)
         {
@@ -381,7 +381,7 @@ complete_diverging_example (symbol_number conflict_sym,
             derivation_list_prepend (result, derivation_new_leaf (*i));
         }
       // completing the derivation
-      derivation *new_deriv = derivation_new (rules[r].lhs->number, result);
+      derivation *new_deriv = derivation_new (r->lhs->number, result);
       result = derivation_list_new ();
       derivation_list_append (result, new_deriv);
     }

src/gram.c

@@ -48,17 +48,6 @@ int max_code = 256;
 
 int required_version = 0;
 
-rule const *
-item_rule (item_number const *item)
-{
-  item_number const *sp = item;
-  while (0 <= *sp)
-    ++sp;
-  rule_number r = item_number_as_rule_number (*sp);
-  return &rules[r];
-}
-
-
 void
 item_print (item_number *item, rule const *previous_rule, FILE *out)
 {

src/gram.h

@@ -237,7 +237,15 @@ print_dot (FILE *out)
 }
 
 /* Get the rule associated to this item.  ITEM points inside RITEM.  */
-rule const *item_rule (item_number const *item);
+static inline rule const *
+item_rule (item_number const *item)
+{
+  item_number const *sp = item;
+  while (!item_number_is_rule_number (*sp))
+    ++sp;
+  rule_number r = item_number_as_rule_number (*sp);
+  return &rules[r];
+}
 
 /* Pretty-print this ITEM (as in the report).  ITEM points inside
    RITEM.  PREVIOUS_RULE is used to see if the lhs is common, in which

src/ielr.c

@@ -418,14 +418,7 @@ ielr_item_has_lookahead (state *s, symbol_number lhs, size_t item,
           /* If the LHS symbol of this item isn't known (because this is a
              top-level invocation), go get it.  */
           if (!lhs)
-            {
-              int i;
-              for (i = s->items[item];
-                   !item_number_is_rule_number (ritem[i]);
-                   ++i)
-                continue;
-              lhs = rules[item_number_as_rule_number (ritem[i])].lhs->number;
-            }
+            lhs = item_rule (&ritem[s->items[item]])->lhs->number;
           /* If this kernel item is next to the beginning of the RHS, then
              check all predecessors' goto follows for the LHS.  */
           if (item_number_is_rule_number (ritem[s->items[item] - 2]))
@@ -633,17 +626,10 @@ ielr_compute_lookaheads (bitsetv follow_kernel_items, bitsetv always_follows,
           && !bitset_empty_p (lookahead_filter[t_item]))
         {
           if (item_number_is_rule_number (ritem[t->items[t_item] - 2]))
-            {
-              int rule_item;
-              for (rule_item = t->items[t_item];
-                   !item_number_is_rule_number (ritem[rule_item]);
-                   ++rule_item)
-                ;
-              ielr_compute_goto_follow_set (
-                follow_kernel_items, always_follows, s,
-                rules[item_number_as_rule_number (ritem[rule_item])].lhs,
-                lookaheads[t_item]);
-            }
+            ielr_compute_goto_follow_set (
+              follow_kernel_items, always_follows, s,
+              item_rule (&ritem[t->items[t_item]])->lhs,
+              lookaheads[t_item]);
           else if (s->lookaheads)
             {
               /* We don't have to start the s item search at the beginning