grammar: record used associativity and print useless ones

Record which symbol associativity is used, and display useless ones.

* src/symtab.h, src/symtab.c (register_assoc, print_assoc_warnings): New
* src/symtab.c (init_assoc, is_assoc_used): New
* src/main.c: Use print_assoc_warnings
* src/conflicts.c: Use register_assoc
* tests/conflicts.at (Useless associativity warning): New.

Due to the new warning, many tests had to be updated.

* tests/conflicts.at tests/existing.at tests/regression.at:
Add the associativity warning in the expected results.
* tests/java.at: Fix the java calculator's grammar to remove a useless
associativity.
* doc/bison.texi (mfcalc example): Fix associativity to remove
warning.

src/conflicts.c

@@ -303,16 +303,19 @@ resolve_sr_conflict (state *s, int ruleno, symbol **errors, int *nerrs)
               break;
 
             case right_assoc:
+              register_assoc (i, redrule->prec->number);
               log_resolution (redrule, i, right_resolution);
               flush_reduce (lookahead_tokens, i);
               break;
 
             case left_assoc:
+              register_assoc (i, redrule->prec->number);
               log_resolution (redrule, i, left_resolution);
               flush_shift (s, i);
               break;
 
             case non_assoc:
+              register_assoc (i, redrule->prec->number);
               log_resolution (redrule, i, nonassoc_resolution);
               flush_shift (s, i);
               flush_reduce (lookahead_tokens, i);

src/main.c

@@ -146,6 +146,8 @@ main (int argc, char *argv[])
 
   print_precedence_warnings ();
 
+  print_assoc_warnings ();
+
   /* Output file names. */
   compute_output_file_names ();
 

src/symtab.c

@@ -52,6 +52,12 @@ location startsymbol_location;
 
 static symgraph **prec_nodes;
 
+/*-----------------------------------.
+| Store which associativity is used. |
+`-----------------------------------*/
+
+bool *used_assoc = NULL;
+
 /*---------------------------------.
 | Create a new symbol, named TAG.  |
 `---------------------------------*/
@@ -1073,3 +1079,61 @@ print_precedence_warnings (void)
                   _("useless precedence for %s"), s->tag);
     }
 }
+
+/*---------------------------------------.
+| Initialize association tracking table. |
+`---------------------------------------*/
+
+static void
+init_assoc (void)
+{
+  graphid i;
+  used_assoc = xcalloc(nsyms, sizeof(*used_assoc));
+  for (i = 0; i < nsyms; ++i)
+    used_assoc[i] = false;
+}
+
+/*------------------------------------------------------------------.
+| Test if the associativity for the symbols is defined and useless. |
+`------------------------------------------------------------------*/
+
+static inline bool
+is_assoc_useless (symbol *s)
+{
+  return s
+      && s->assoc != undef_assoc
+      && s->assoc != precedence_assoc
+      && !used_assoc[s->number];
+}
+
+/*-------------------------------.
+| Register a used associativity. |
+`-------------------------------*/
+
+void
+register_assoc (graphid i, graphid j)
+{
+  if (!used_assoc)
+    init_assoc ();
+  used_assoc[i] = true;
+  used_assoc[j] = true;
+}
+
+/*------------------------------------------------------.
+| Print a warning for each unused symbol associativity. |
+`------------------------------------------------------*/
+
+void
+print_assoc_warnings (void)
+{
+  graphid i;
+  if (!used_assoc)
+    init_assoc ();
+  for (i = 0; i < nsyms; ++i)
+    {
+      symbol *s = symbols[i];
+      if (is_assoc_useless (s))
+        complain (&s->location, Wother,
+                  _("useless associativity for %s"), s->tag);
+    }
+}

src/symtab.h

@@ -270,6 +270,14 @@ void register_precedence (graphid first, graphid snd);
 
 void print_precedence_warnings (void);
 
+/*----------------------.
+| Symbol associativity  |
+`----------------------*/
+
+void register_assoc (int i, int j);
+
+void print_assoc_warnings (void);
+
 /*-----------------.
 | Semantic types.  |
 `-----------------*/