From e51fd547ca70894069d8b9d7100ec5309f6c0e3f Mon Sep 17 00:00:00 2001
From: Akim Demaille <akim.demaille@gmail.com>
Date: Wed, 7 Nov 2018 22:27:35 +0100
Subject: [PATCH] %expect: tune the number of conflicts per rule

Currently on a grammar such as

    exp: "number" | exp "+" exp | exp "*" exp

we count only one sr-conflict for both binary rules, i.e., we expect:

    exp: "number" | exp "+" exp  %expect 1 | exp "*" exp  %expect 1

although there are 4 conflicts in total.  That's because in the states
in conflict, for instance that for the "+" rule:

    State 6

        2 exp: exp . "+" exp
        2    | exp "+" exp .  [$end, "+", "*"]
        3    | exp . "*" exp

        "+"  shift, and go to state 4
        "*"  shift, and go to state 5

        "+"       [reduce using rule 2 (exp)]
        "*"       [reduce using rule 2 (exp)]
        $default  reduce using rule 2 (exp)

we count only a single conflict, although there are two (one on "+"
and another with "*").

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

* src/conflicts.c (rule_has_state_sr_conflicts): Rename as...
(count_rule_state_sr_conflicts): this.
DWIM.
(count_rule_sr_conflicts): Adjust.
* tests/conflicts.at (%expect in grammar rules): New.
---
 src/conflicts.c    | 28 ++++++++++++++++------------
 tests/conflicts.at | 19 +++++++++++++++++++
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/src/conflicts.c b/src/conflicts.c
index 5e7268a7..2838243e 100644
--- a/src/conflicts.c
+++ b/src/conflicts.c
@@ -504,14 +504,15 @@ count_rr_conflicts (bool one_per_token)
 }
 
 
-/*----------------------------------------------------------------------.
-| For a given rule, count the number of states for which it is involved |
-| in shift/reduce conflicts.                                            |
-`----------------------------------------------------------------------*/
+/*------------------------------------------------------------------.
+| For a given rule, the number of shift/reduce conflicts in a given |
+| state.                                                            |
+`------------------------------------------------------------------*/
 
-static bool
-rule_has_state_sr_conflicts (rule *r, state *s)
+static size_t
+count_rule_state_sr_conflicts (rule *r, state *s)
 {
+  size_t res = 0;
   transitions *trans = s->transitions;
   reductions *reds = s->reductions;
 
@@ -521,21 +522,24 @@ rule_has_state_sr_conflicts (rule *r, state *s)
         bitset lookaheads = reds->lookahead_tokens[i];
         int j;
         FOR_EACH_SHIFT (trans, j)
-          if (bitset_test (lookaheads, TRANSITION_SYMBOL (trans, j)))
-            return true;
-        break;
+          res += bitset_test (lookaheads, TRANSITION_SYMBOL (trans, j));
       }
 
-  return false;
+  return res;
 }
 
+/*----------------------------------------------------------------------.
+| For a given rule, count the number of states for which it is involved |
+| in shift/reduce conflicts.                                            |
+`----------------------------------------------------------------------*/
+
 static size_t
 count_rule_sr_conflicts (rule *r)
 {
   size_t res = 0;
   for (state_number i = 0; i < nstates; ++i)
-    if (conflicts[i] && rule_has_state_sr_conflicts (r, states[i]))
-      res++;
+    if (conflicts[i])
+      res += count_rule_state_sr_conflicts (r, states[i]);
   return res;
 }
 
diff --git a/tests/conflicts.at b/tests/conflicts.at
index 91cf9e77..c5fd512f 100644
--- a/tests/conflicts.at
+++ b/tests/conflicts.at
@@ -1280,6 +1280,25 @@ AT_BISON_CHECK([-o input.c input.y])
 AT_CLEANUP
 
 
+## -------------------------- ##
+## %expect in grammar rules.  ##
+## -------------------------- ##
+
+AT_SETUP([%expect in grammar rules])
+
+AT_DATA([input.y],
+[[%expect 4
+%%
+exp:
+  "number"
+| exp "+" exp  %expect 2
+| exp "*" exp  %expect 2
+]])
+
+AT_BISON_CHECK([-o input.c -rall input.y])
+AT_CLEANUP
+
+
 ## ---------------------------------- ##
 ## %expect in grammar rule too much.  ##
 ## ---------------------------------- ##