%expect-rr: tune the number of conflicts per rule

Currently on a grammar such as

    exp : a '1' | a '2' | a '3' | b '1' | b '2' | b '3'
    a:
    b:

we count only one rr-conflict on the `b:` rule, i.e., we expect:

    b: %expect-rr 1

although there are 3 conflicts in total.  That's because in the
conflicted state we count only a single conflict, not three (one for
each of the lookaheads: '1', '2', '3').

    State 0

        0 $accept: . exp $end
        1 exp: . a '1'
        2    | . a '2'
        3    | . a '3'
        4    | . b '1'
        5    | . b '2'
        6    | . b '3'
        7 a: . %empty  ['1', '2', '3']
        8 b: . %empty  ['1', '2', '3']

        '1'       reduce using rule 7 (a)
        '1'       [reduce using rule 8 (b)]
        '2'       reduce using rule 7 (a)
        '2'       [reduce using rule 8 (b)]
        '3'       reduce using rule 7 (a)
        '3'       [reduce using rule 8 (b)]
        $default  reduce using rule 7 (a)

        exp  go to state 1
        a    go to state 2
        b    go to state 3

See https://lists.gnu.org/archive/html/bison-patches/2013-02/msg00106.html.

* src/conflicts.c (rule_has_state_rr_conflicts): Rename as...
(count_rule_state_sr_conflicts): this.
DWIM.
(count_rule_rr_conflicts): Adjust.
* tests/conflicts.at (%expect-rr in grammar rules)
(%expect-rr too much in grammar rules)
(%expect-rr not enough in grammar rules): New.

src/conflicts.c

@@ -483,7 +483,7 @@ count_state_rr_conflicts (state *s)
       int count = 0;
       for (int j = 0; j < reds->num; ++j)
         count += bitset_test (reds->lookahead_tokens[j], i);
-      if (count >= 2)
+      if (2 <= count)
         res += count-1;
     }
 
@@ -546,23 +546,25 @@ count_rule_sr_conflicts (rule *r)
 | involved in reduce/reduce conflicts.                             |
 `-----------------------------------------------------------------*/
 
-static bool
-rule_has_state_rr_conflicts (rule *r, state *s)
+static size_t
+count_rule_state_rr_conflicts (rule *r, state *s)
 {
-  reductions *reds = s->reductions;
+  size_t res = 0;
+  const reductions *reds = s->reductions;
+  bitset lookaheads = bitset_create (ntokens, BITSET_FIXED);
 
   for (int i = 0; i < reds->num; ++i)
     if (reds->rules[i] == r)
-      {
-        bitset lookaheads = reds->lookahead_tokens[i];
       for (int j = 0; j < reds->num; ++j)
-          if (reds->rules[j] != r &&
-              !bitset_disjoint_p (lookaheads, reds->lookahead_tokens[j]))
-            return true;
-        break;
+        if (reds->rules[j] != r)
+          {
+            bitset_and (lookaheads,
+                        reds->lookahead_tokens[i],
+                        reds->lookahead_tokens[j]);
+            res += bitset_count (lookaheads);
           }
-
-  return false;
+  bitset_free (lookaheads);
+  return res;
 }
 
 static size_t
@@ -570,8 +572,7 @@ count_rule_rr_conflicts (rule *r)
 {
   size_t res = 0;
   for (state_number i = 0; i < nstates; ++i)
-    if (conflicts[i] && rule_has_state_rr_conflicts (r, states[i]))
-      res++;
+    res += count_rule_state_rr_conflicts (r, states[i]);
   return res;
 }
 

tests/conflicts.at

@@ -1318,6 +1318,89 @@ AT_BISON_CHECK([-o input.c input.y], 1, [],
 AT_CLEANUP
 
 
+## ---------------------------- ##
+## %expect-rr in grammar rule.  ##
+## ---------------------------- ##
+
+AT_SETUP([%expect-rr in grammar rule])
+
+AT_DATA([input.y],
+[[%glr-parser
+%expect-rr 3
+%%
+exp
+: a '1'
+| a '2'
+| a '3'
+| b '1'
+| b '2'
+| b '3'
+a:
+b: %expect-rr 3
+]])
+
+AT_BISON_CHECK([-o input.c input.y])
+AT_CLEANUP
+
+
+## ------------------------------------- ##
+## %expect-rr too much in grammar rule.  ##
+## ------------------------------------- ##
+
+AT_SETUP([%expect-rr too much in grammar rule])
+
+AT_DATA([input.y],
+[[%glr-parser
+%expect-rr 3
+%%
+exp
+: a '1'
+| a '2'
+| a '3'
+| b '1'
+| b '2'
+| b '3'
+a:
+b: %expect-rr 4
+]])
+
+AT_BISON_CHECK([-fcaret -o input.c input.y], 1, [],
+[[input.y:12.4-15: error: reduce/reduce conflicts for rule 8: 3 found, 4 expected
+ b: %expect-rr 4
+    ^^^^^^^^^^^^
+]])
+AT_CLEANUP
+
+
+## --------------------------------------- ##
+## %expect-rr not enough in grammar rule.  ##
+## --------------------------------------- ##
+
+AT_SETUP([%expect-rr not enough in grammar rule])
+
+AT_DATA([input.y],
+[[%glr-parser
+%expect-rr 3
+%%
+exp
+: a '1'
+| a '2'
+| a '3'
+| b '1'
+| b '2'
+| b '3'
+a:
+b: %expect-rr 2
+]])
+
+AT_BISON_CHECK([-fcaret -o input.c input.y], 1, [],
+[[input.y:12.4-15: error: reduce/reduce conflicts for rule 8: 3 found, 2 expected
+ b: %expect-rr 2
+    ^^^^^^^^^^^^
+]])
+AT_CLEANUP
+
+
 ## ------------------------- ##
 ## %prec with user strings.  ##
 ## ------------------------- ##