gram: fix and improve log message

[Akim Demaille]

commit 53a0510825a2bd6887b2bb41eb8ee31db43db472
Author: Akim Demaille <address@hidden>
Date:   Fri Mar 29 21:49:50 2019 +0100

    gram: fix and improve log message
    
    It seems that not many people read these logs: the error was
    introduced in 2001 (3067fbef531832df1e43bbd28787655808361eed),
    
    * src/gram.c (grammar_dump): Fix the headers of the table: remove
    duplicate display of "Ritem Range".
    While at it, remove duplicate display of the rule number (and remove
    an incorrect comment about it: these numbers _are_ equal).
    * tests/sets.at (Reduced Grammar): Use useless rule, nterm and token
    in the example.

diff --git a/src/gram.c b/src/gram.c
index b580dac4..dd25da34 100644
--- a/src/gram.c
+++ b/src/gram.c
@@ -274,25 +274,23 @@ grammar_dump (FILE *out, const char *title)
 
   fprintf (out, "Rules\n-----\n\n");
   {
-    /* Reduced number, then original number in the sources.  */
     fprintf (out,
-             "Num (Num, Prec, Assoc, Useful, UselessChain, Ritem Range)"
-             " Lhs -> Rhs (Ritem range)\n");
+             "Num (Prec, Assoc, Useful, UselessChain) Lhs"
+             " -> (Ritem Range) Rhs\n");
     for (rule_number i = 0; i < nrules + nuseless_productions; ++i)
       {
         rule const *rule_i = &rules[i];
         unsigned const rhs_itemno = rule_i->rhs - ritem;
         unsigned length = rule_rhs_length (rule_i);
-        fprintf (out, "%3d (%3d, %2d, %2d, %2s, %2s, %2u-%2u)   %2d ->",
-                 item_number_as_rule_number (rule_i->rhs[length]),
+        aver (item_number_as_rule_number (rule_i->rhs[length] == i));
+        fprintf (out, "%3d (%2d, %2d, %2s, %2s)   %2d -> (%2u-%2u)",
                  i,
                  rule_i->prec ? rule_i->prec->prec : 0,
                  rule_i->prec ? rule_i->prec->assoc : 0,
                  rule_i->useful ? "t" : "f",
                  rule_useless_chain_p (rule_i) ? "t" : "f",
-                 rhs_itemno,
-                 rhs_itemno + length - 1,
-                 rule_i->lhs->number);
+                 rule_i->lhs->number,
+                 rhs_itemno, rhs_itemno + length - 1);
         /* Dumped the RHS. */
         for (item_number *rhsp = rule_i->rhs; 0 <= *rhsp; ++rhsp)
           fprintf (out, " %3d", *rhsp);
diff --git a/tests/sets.at b/tests/sets.at
index c9feb9d8..3ad1a855 100644
--- a/tests/sets.at
+++ b/tests/sets.at
@@ -315,34 +315,39 @@ AT_DATA([input.y],
 [[%%
 expr: expr "+" term | term
 term: term "*" fact | fact
+useless: "useless"
 fact: "num"
 ]])
 
 AT_BISON_CHECK([[--trace=grammar -o input.c input.y]], [], [],
-[[Reduced Grammar
+[[input.y: warning: 1 nonterminal useless in grammar [-Wother]
+input.y: warning: 1 rule useless in grammar [-Wother]
+input.y:4.1-7: warning: nonterminal useless in grammar: useless [-Wother]
+Reduced Grammar
 
-ntokens = 6, nvars = 4, nsyms = 10, nrules = 6, nritems = 17
+ntokens = 7, nvars = 4, nsyms = 11, nrules = 6, nritems = 17
 
 Variables
 ---------
 
 Value  Sprec  Sassoc  Tag
-    6      0       0  $accept
-    7      0       0  expr
-    8      0       0  term
-    9      0       0  fact
+    7      0       0  $accept
+    8      0       0  expr
+    9      0       0  term
+   10      0       0  fact
 
 
 Rules
 -----
 
-Num (Num, Prec, Assoc, Useful, UselessChain, Ritem Range) Lhs -> Rhs (Ritem 
range)
-  0 (  0,  0,  0,  t,  f,  0- 1)    6 ->   7   0
-  1 (  1,  0,  0,  t,  f,  3- 5)    7 ->   7   3   8
-  2 (  2,  0,  0,  t,  t,  7- 7)    7 ->   8
-  3 (  3,  0,  0,  t,  f,  9-11)    8 ->   8   4   9
-  4 (  4,  0,  0,  t,  t, 13-13)    8 ->   9
-  5 (  5,  0,  0,  t,  t, 15-15)    9 ->   5
+Num (Prec, Assoc, Useful, UselessChain) Lhs -> (Ritem Range) Rhs
+  0 ( 0,  0,  t,  f)    7 -> ( 0- 1)   8   0
+  1 ( 0,  0,  t,  f)    8 -> ( 3- 5)   8   3   9
+  2 ( 0,  0,  t,  t)    8 -> ( 7- 7)   9
+  3 ( 0,  0,  t,  f)    9 -> ( 9-11)   9   4  10
+  4 ( 0,  0,  t,  t)    9 -> (13-13)  10
+  5 ( 0,  0,  t,  t)   10 -> (17-17)   6
+  6 ( 0,  0,  f,  t)   11 -> (15-15)   5
 
 
 Rules interpreted
@@ -354,9 +359,10 @@ Rules interpreted
 3      term: term "*" fact
 4      term: fact
 5      fact: "num"
+6      useless: "useless"
 
 
-reduced input.y defines 6 terminals, 4 nonterminals, and 6 productions.
+reduced input.y defines 7 terminals, 4 nonterminals, and 6 productions.
 ]])
 
 AT_CLEANUP