Get action warnings (grammar_rule_check) right even when symbol

declarations appear after the rules.  Don't mistake the type of $$ in
a midrule to be that of its parent rule's $$.
* src/reader.c (grammar_current_rule_end): Don't invoke
grammar_rule_check yet since not all symbol declarations may have been
parsed yet.
(grammar_midrule_action): Likewise.
Don't record whether the midrule's $$ has been used yet since actions
haven't been translated yet.
Record the midrule's parent rule and its RHS index within the parent
rule.
(grammar_current_rule_action_append): Don't translate the action yet
since not all symbol declarations may have been parsed yet and, thus,
warnings about types for $$, $n, @$, and @n can't be reported yet.
(packgram): Translate the action and invoke grammar_rule_check now that
all symbol declarations have been parsed.
* src/scan-code.l (handle_action_dollar): Now that this is invoked
after parsing the entire grammar file, the symbol list here in the case
of a midrule is actually the midrule's empty RHS, so reference its
parent rule's RHS where necessary.
On the other hand, now that you can already know it's a midrule, you
aren't forced to think $$ has the same type as its parent rule's $$.
(handle_action_at): In the case of a midrule, reference the parent rule
where necessary.
* src/symlist.c (symbol_list_new): Initialize new midrule-related
members.
(symbol_list_length): Now that this is invoked after all rules have
been parsed, a NULL symbol (rather than a NULL symbol list node)
terminates a rule.  symbol_list_print already does this correctly.
* src/symlist.h (symbol_list.midrule_parent_rule,
symbol_list.midrule_parent_rhs_index): New members so that midrules can
remember their relationships with their parents.
* tests/input.at (Type Clashes): Extend to catch the midrule $$ error
fixed by the above patch.
(_AT_UNUSED_VALUES_DECLARATIONS, AT_CHECK_UNUSED_VALUES): New m4 macros
implementing...
(Unused values): ... this old test case and...
(Unused values before symbol declarations): ... this new test case.
This one is the same as `Unused values' except that all symbol
declarations appear after the rules in order to catch the rest of the
errors fixed by the above patch.

src/reader.c

@@ -293,7 +293,6 @@ grammar_current_rule_end (location loc)
   /* Put an empty link in the list to mark the end of this rule  */
   grammar_symbol_append (NULL, grammar_end->location);
   current_rule->location = loc;
-  grammar_rule_check (current_rule);
 }
 
 
@@ -326,10 +325,9 @@ grammar_midrule_action (void)
   midrule->action = current_rule->action;
   midrule->action_location = dummy_location;
   current_rule->action = NULL;
-  /* If $$ was used in the action, the LHS of the enclosing rule was
-     incorrectly flagged as used.  */
-  midrule->used = current_rule->used;
-  current_rule->used = false;
+  /* The action has not been translated yet, so $$ use hasn't been
+     detected yet.  */
+  midrule->used = false;
 
   if (previous_rule_end)
     previous_rule_end->next = midrule;
@@ -338,7 +336,6 @@ grammar_midrule_action (void)
 
   /* End the dummy's rule.  */
   midrule->next = symbol_list_new (NULL, dummy_location);
-  grammar_rule_check (midrule);
   midrule->next->next = current_rule;
 
   previous_rule_end = midrule->next;
@@ -347,6 +344,8 @@ grammar_midrule_action (void)
      the current rule.  Bind it to its dedicated rule.  */
   grammar_current_rule_symbol_append (dummy, dummy_location);
   grammar_end->midrule = midrule;
+  midrule->midrule_parent_rule = current_rule;
+  midrule->midrule_parent_rhs_index = symbol_list_length (current_rule->next);
 }
 
 /* Set the precedence symbol of the current rule to PRECSYM. */
@@ -405,9 +404,10 @@ grammar_current_rule_action_append (const char *action, location loc)
 {
   if (current_rule->action)
     grammar_midrule_action ();
+  /* After all symbol declarations have been parsed, packgram invokes
+     translate_rule_action.  */
   current_rule->action = action;
   current_rule->action_location = loc;
-  current_rule->action = translate_rule_action (current_rule);
 }
 
 
@@ -444,9 +444,16 @@ packgram (void)
       rules[ruleno].precsym = NULL;
       rules[ruleno].location = p->location;
       rules[ruleno].useful = true;
-      rules[ruleno].action = p->action;
+      rules[ruleno].action = p->action ? translate_rule_action (p) : NULL;
       rules[ruleno].action_location = p->action_location;
 
+      /* If this rule contains midrules, rest assured that
+        grammar_midrule_action inserted the midrules into grammar before this
+        rule.  Thus, the midrule actions have already been scanned in order to
+        set `used' flags for this rule's rhs, so grammar_rule_check will work
+        properly.  */
+      grammar_rule_check (p);
+
       for (p = p->next; p && p->sym; p = p->next)
 	{
 	  ++rule_length;

src/scan-code.l

@@ -240,7 +240,19 @@ handle_action_dollar (symbol_list *rule, char *text, location dollar_loc)
 {
   const char *type_name = NULL;
   char *cp = text + 1;
-  int rule_length = symbol_list_length (rule->next);
+  symbol_list *effective_rule;
+  int effective_rule_length;
+
+  if (rule->midrule_parent_rule)
+    {
+      effective_rule = rule->midrule_parent_rule;
+      effective_rule_length = rule->midrule_parent_rhs_index - 1;
+    }
+  else
+    {
+      effective_rule = rule;
+      effective_rule_length = symbol_list_length (rule->next);
+    }
 
   /* Get the type name if explicit. */
   if (*cp == '<')
@@ -257,8 +269,17 @@ handle_action_dollar (symbol_list *rule, char *text, location dollar_loc)
       if (!type_name)
 	type_name = symbol_list_n_type_name_get (rule, dollar_loc, 0);
       if (!type_name && typed)
-	complain_at (dollar_loc, _("$$ of `%s' has no declared type"),
-		     rule->sym->tag);
+       {
+	 if (rule->midrule_parent_rule)
+	   complain_at (dollar_loc,
+			_("$$ for the midrule at $%d of `%s' has no declared"
+			  " type"),
+			rule->midrule_parent_rhs_index,
+			effective_rule->sym->tag);
+	 else
+	   complain_at (dollar_loc, _("$$ of `%s' has no declared type"),
+			rule->sym->tag);
+       }
       if (!type_name)
 	type_name = "";
       obstack_fgrow1 (&obstack_for_string,
@@ -270,23 +291,23 @@ handle_action_dollar (symbol_list *rule, char *text, location dollar_loc)
       long int num;
       set_errno (0);
       num = strtol (cp, 0, 10);
-      if (INT_MIN <= num && num <= rule_length && ! get_errno ())
+      if (INT_MIN <= num && num <= effective_rule_length && ! get_errno ())
 	{
 	  int n = num;
 	  if (1-n > max_left_semantic_context)
 	    max_left_semantic_context = 1-n;
 	  if (!type_name && n > 0)
 	    type_name =
-	      symbol_list_n_type_name_get (rule, dollar_loc, n);
+	      symbol_list_n_type_name_get (effective_rule, dollar_loc, n);
 	  if (!type_name && typed)
 	    complain_at (dollar_loc, _("$%d of `%s' has no declared type"),
-			 n, rule->sym->tag);
+			 n, effective_rule->sym->tag);
 	  if (!type_name)
 	    type_name = "";
 	  obstack_fgrow3 (&obstack_for_string,
 			  "]b4_rhs_value(%d, %d, [%s])[",
-			  rule_length, n, type_name);
-	  symbol_list_n_used_set (rule, n, true);
+			  effective_rule_length, n, type_name);
+	  symbol_list_n_used_set (effective_rule, n, true);
 	}
       else
 	complain_at (dollar_loc, _("integer out of range: %s"), quote (text));
@@ -303,8 +324,13 @@ static void
 handle_action_at (symbol_list *rule, char *text, location at_loc)
 {
   char *cp = text + 1;
-  int rule_length = symbol_list_length (rule->next);
   locations_flag = true;
+  int effective_rule_length;
+
+  if (rule->midrule_parent_rule)
+    effective_rule_length = rule->midrule_parent_rhs_index - 1;
+  else
+    effective_rule_length = symbol_list_length (rule->next);
 
   if (*cp == '$')
     obstack_sgrow (&obstack_for_string, "]b4_lhs_location[");
@@ -314,11 +340,11 @@ handle_action_at (symbol_list *rule, char *text, location at_loc)
       set_errno (0);
       num = strtol (cp, 0, 10);
 
-      if (INT_MIN <= num && num <= rule_length && ! get_errno ())
+      if (INT_MIN <= num && num <= effective_rule_length && ! get_errno ())
 	{
 	  int n = num;
 	  obstack_fgrow2 (&obstack_for_string, "]b4_rhs_location(%d, %d)[",
-			  rule_length, n);
+			  effective_rule_length, n);
 	}
       else
 	complain_at (at_loc, _("integer out of range: %s"), quote (text));

src/symlist.c

@@ -39,6 +39,8 @@ symbol_list_new (symbol *sym, location loc)
   res->location = loc;
 
   res->midrule = NULL;
+  res->midrule_parent_rule = NULL;
+  res->midrule_parent_rhs_index = 0;
 
   res->action = NULL;
   res->used = false;
@@ -102,7 +104,7 @@ unsigned int
 symbol_list_length (const symbol_list *l)
 {
   int res = 0;
-  for (/* Nothing. */; l; l = l->next)
+  for (/* Nothing. */; l && l->sym; l = l->next)
     ++res;
   return res;
 }

src/symlist.h

@@ -32,10 +32,17 @@ typedef struct symbol_list
   symbol *sym;
   location location;
 
-  /* If this symbol is the generated lhs for a mid-rule, a pointer to
-     that mid-rule.  */
+  /* If this symbol is the generated lhs for a midrule but this is the rule in
+     whose rhs it appears, MIDRULE = a pointer to that midrule.  */
   struct symbol_list *midrule;
 
+  /* If this symbol is the generated lhs for a midrule and this is that
+     midrule, MIDRULE_PARENT_RULE = a pointer to the rule in whose rhs it
+     appears, and MIDRULE_PARENT_RHS_INDEX = its rhs index (1-origin) in the
+     parent rule.  */
+  struct symbol_list *midrule_parent_rule;
+  int midrule_parent_rhs_index;
+
   /* The action is attached to the LHS of a rule. */
   const char *action;
   location action_location;