maint: run "make update-copyright"

[bison.git] / tests / conflicts.at

# Exercising Bison on conflicts.                         -*- Autotest -*-

# Copyright (C) 2002-2005, 2007, 2009-2010 Free Software Foundation,
# Inc.

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

AT_BANNER([[Conflicts.]])


## ---------------- ##
## S/R in initial.  ##
## ---------------- ##

# I once hacked Bison in such a way that it lost its reductions on the
# initial state (because it was confusing it with the last state).  It
# took me a while to strip down my failures to this simple case.  So
# make sure it finds the s/r conflict below.

AT_SETUP([S/R in initial])

AT_DATA([[input.y]],
[[%expect 1
%%
exp: e 'e';
e: 'e' | /* Nothing. */;
]])

AT_BISON_CHECK([-o input.c input.y], 0, [],
[[input.y:4.9: warning: rule useless in parser due to conflicts: e: /* empty */
]])

AT_CLEANUP


## ------------------- ##
## %nonassoc and eof.  ##
## ------------------- ##

AT_SETUP([%nonassoc and eof])

AT_DATA_GRAMMAR([input.y],
[[
%{
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define YYERROR_VERBOSE 1
static void
yyerror (const char *msg)
{
  fprintf (stderr, "%s\n", msg);
}

/* The current argument. */
static const char *input;

static int
yylex (void)
{
  static size_t toknum;
  if (! (toknum <= strlen (input)))
    abort ();
  return input[toknum++];
}

%}

%nonassoc '<' '>'

%%
expr: expr '<' expr
    | expr '>' expr
    | '0'
    ;
%%
int
main (int argc, const char *argv[])
{
  input = argc <= 1 ? "" : argv[1];
  return yyparse ();
}
]])

# Specify the output files to avoid problems on different file systems.
AT_BISON_CHECK([-o input.c input.y])
AT_COMPILE([input])

AT_PARSER_CHECK([./input '0<0'])
AT_PARSER_CHECK([./input '0<0<0'], [1], [],
         [syntax error, unexpected '<'
])

AT_PARSER_CHECK([./input '0>0'])
AT_PARSER_CHECK([./input '0>0>0'], [1], [],
         [syntax error, unexpected '>'
])

AT_PARSER_CHECK([./input '0<0>0'], [1], [],
         [syntax error, unexpected '>'
])

# We must disable default reductions in inconsistent states in order to
# have an explicit list of all expected tokens.  (However, unless we use
# canonical LR, lookahead sets are merged for different left contexts,
# so it is still possible to have extra incorrect tokens in the expected
# list.  That just doesn't happen to be a problem for this test case.)

AT_BISON_CHECK([-Dlr.default-reductions=consistent -o input.c input.y])
AT_COMPILE([input])

AT_PARSER_CHECK([./input '0<0'])
AT_PARSER_CHECK([./input '0<0<0'], [1], [],
         [syntax error, unexpected '<', expecting $end
])

AT_PARSER_CHECK([./input '0>0'])
AT_PARSER_CHECK([./input '0>0>0'], [1], [],
         [syntax error, unexpected '>', expecting $end
])

AT_PARSER_CHECK([./input '0<0>0'], [1], [],
         [syntax error, unexpected '>', expecting $end
])

AT_CLEANUP



## -------------------------------------- ##
## %error-verbose and consistent errors.  ##
## -------------------------------------- ##

AT_SETUP([[%error-verbose and consistent errors]])

m4_pushdef([AT_CONSISTENT_ERRORS_CHECK], [

AT_BISON_CHECK([$1[ -o input.c input.y]])
AT_COMPILE([[input]])

m4_pushdef([AT_EXPECTING], [m4_if($3, [ab], [[, expecting 'a' or 'b']],
                                  $3, [a],  [[, expecting 'a']],
                                  $3, [b],  [[, expecting 'b']])])

AT_PARSER_CHECK([[./input]], [[1]], [],
[[syntax error, unexpected ]$2[]AT_EXPECTING[
]])

m4_popdef([AT_EXPECTING])

])

AT_DATA_GRAMMAR([input.y],
[[%code {
  #include <assert.h>
  #include <stdio.h>
  int yylex (void);
  void yyerror (char const *);
  #define USE(Var)
}

%error-verbose

// The point isn't to test IELR here, but state merging happens to
// complicate the example.
%define lr.type ielr

%nonassoc 'a'

// If yylval=0 here, then we know that the 'a' destructor is being
// invoked incorrectly for the 'b' set in the semantic action below.
// All 'a' tokens are returned by yylex, which sets yylval=1.
%destructor {
  if (!$$)
    fprintf (stderr, "Wrong destructor.\n");
} 'a'

%%

// The lookahead assigned by the semantic action isn't needed before
// either error action is encountered.  In a previous version of Bison,
// this was a problem as it meant yychar was not translated into yytoken
// before either error action.  The second error action thus invoked a
// destructor that it selected according to the incorrect yytoken.  The
// first error action would have reported an incorrect unexpected token
// except that, due to another bug, the unexpected token is not reported
// at all because the error action is the default action in a consistent
// state.  That bug still needs to be fixed.
start: error-reduce consistent-error 'a' { USE ($3); } ;

error-reduce:
  'a' 'a' consistent-reduction consistent-error 'a'
  { USE (($1, $2, $5)); }
| 'a' error
  { USE ($1); }
;

consistent-reduction: /*empty*/ {
  assert (yychar == YYEMPTY);
  yylval = 0;
  yychar = 'b';
} ;

consistent-error:
  'a' { USE ($1); }
| /*empty*/ %prec 'a'
;

// Provide another context in which all rules are useful so that this
// test case looks a little more realistic.
start: 'b' consistent-error 'b' ;

%%

int
yylex (void)
{
  static char const *input = "aa";
  yylval = 1;
  return *input++;
}

void
yyerror (char const *msg)
{
  fprintf (stderr, "%s\n", msg);
}

int
main (void)
{
  return yyparse ();
}
]])

# See comments in grammar for why this test doesn't succeed.
AT_XFAIL_IF([[:]])

AT_CONSISTENT_ERRORS_CHECK([], [['b']], [[none]])
AT_CONSISTENT_ERRORS_CHECK([[-Dlr.default-reductions=consistent]],
                           [['b']], [[none]])

# Canonical LR doesn't foresee the error for 'a'!
AT_CONSISTENT_ERRORS_CHECK([[-Dlr.default-reductions=accepting]],
                           [[$end]], [[a]])
AT_CONSISTENT_ERRORS_CHECK([[-Flr.type=canonical-lr]], [[$end]], [[a]])

m4_popdef([AT_CONSISTENT_ERRORS_CHECK])

AT_CLEANUP



## ------------------------- ##
## Unresolved SR Conflicts.  ##
## ------------------------- ##

AT_SETUP([Unresolved SR Conflicts])

AT_KEYWORDS([report])

AT_DATA([input.y],
[[%token NUM OP
%%
exp: exp OP exp | NUM;
]])

AT_BISON_CHECK([-o input.c --report=all input.y], 0, [],
[input.y: conflicts: 1 shift/reduce
])

# Check the contents of the report.
AT_CHECK([cat input.output], [],
[[State 5 conflicts: 1 shift/reduce


Grammar

    0 $accept: exp $end

    1 exp: exp OP exp
    2    | NUM


Terminals, with rules where they appear

$end (0) 0
error (256)
NUM (258) 2
OP (259) 1


Nonterminals, with rules where they appear

$accept (5)
    on left: 0
exp (6)
    on left: 1 2, on right: 0 1


state 0

    0 $accept: . exp $end
    1 exp: . exp OP exp
    2    | . NUM

    NUM  shift, and go to state 1

    exp  go to state 2


state 1

    2 exp: NUM .

    $default  reduce using rule 2 (exp)


state 2

    0 $accept: exp . $end
    1 exp: exp . OP exp

    $end  shift, and go to state 3
    OP    shift, and go to state 4


state 3

    0 $accept: exp $end .

    $default  accept


state 4

    1 exp: . exp OP exp
    1    | exp OP . exp
    2    | . NUM

    NUM  shift, and go to state 1

    exp  go to state 5


state 5

    1 exp: exp . OP exp
    1    | exp OP exp .  [$end, OP]

    OP  shift, and go to state 4

    OP        [reduce using rule 1 (exp)]
    $default  reduce using rule 1 (exp)
]])

AT_CLEANUP



## ----------------------- ##
## Resolved SR Conflicts.  ##
## ----------------------- ##

AT_SETUP([Resolved SR Conflicts])

AT_KEYWORDS([report])

AT_DATA([input.y],
[[%token NUM OP
%left OP
%%
exp: exp OP exp | NUM;
]])

AT_BISON_CHECK([-o input.c --report=all input.y])

# Check the contents of the report.
AT_CHECK([cat input.output], [],
[[Grammar

    0 $accept: exp $end

    1 exp: exp OP exp
    2    | NUM


Terminals, with rules where they appear

$end (0) 0
error (256)
NUM (258) 2
OP (259) 1


Nonterminals, with rules where they appear

$accept (5)
    on left: 0
exp (6)
    on left: 1 2, on right: 0 1


state 0

    0 $accept: . exp $end
    1 exp: . exp OP exp
    2    | . NUM

    NUM  shift, and go to state 1

    exp  go to state 2


state 1

    2 exp: NUM .

    $default  reduce using rule 2 (exp)


state 2

    0 $accept: exp . $end
    1 exp: exp . OP exp

    $end  shift, and go to state 3
    OP    shift, and go to state 4


state 3

    0 $accept: exp $end .

    $default  accept


state 4

    1 exp: . exp OP exp
    1    | exp OP . exp
    2    | . NUM

    NUM  shift, and go to state 1

    exp  go to state 5


state 5

    1 exp: exp . OP exp
    1    | exp OP exp .  [$end, OP]

    $default  reduce using rule 1 (exp)

    Conflict between rule 1 and token OP resolved as reduce (%left OP).
]])

AT_CLEANUP


## -------------------------------- ##
## Defaulted Conflicted Reduction.  ##
## -------------------------------- ##

# When there are RR conflicts, some rules are disabled.  Usually it is
# simply displayed as:
#
#    $end           reduce using rule 3 (num)
#    $end           [reduce using rule 4 (id)]
#
# But when `reduce 3' is the default action, we'd produce:
#
#    $end           [reduce using rule 4 (id)]
#    $default    reduce using rule 3 (num)
#
# In this precise case (a reduction is masked by the default
# reduction), we make the `reduce 3' explicit:
#
#    $end           reduce using rule 3 (num)
#    $end           [reduce using rule 4 (id)]
#    $default    reduce using rule 3 (num)
#
# Maybe that's not the best display, but then, please propose something
# else.

AT_SETUP([Defaulted Conflicted Reduction])
AT_KEYWORDS([report])

AT_DATA([input.y],
[[%%
exp: num | id;
num: '0';
id : '0';
%%
]])

AT_BISON_CHECK([-o input.c --report=all input.y], 0, [],
[[input.y: conflicts: 1 reduce/reduce
input.y:4.6-8: warning: rule useless in parser due to conflicts: id: '0'
]])

# Check the contents of the report.
AT_CHECK([cat input.output], [],
[[Rules useless in parser due to conflicts

    4 id: '0'


State 1 conflicts: 1 reduce/reduce


Grammar

    0 $accept: exp $end

    1 exp: num
    2    | id

    3 num: '0'

    4 id: '0'


Terminals, with rules where they appear

$end (0) 0
'0' (48) 3 4
error (256)


Nonterminals, with rules where they appear

$accept (4)
    on left: 0
exp (5)
    on left: 1 2, on right: 0
num (6)
    on left: 3, on right: 1
id (7)
    on left: 4, on right: 2


state 0

    0 $accept: . exp $end
    1 exp: . num
    2    | . id
    3 num: . '0'
    4 id: . '0'

    '0'  shift, and go to state 1

    exp  go to state 2
    num  go to state 3
    id   go to state 4


state 1

    3 num: '0' .  [$end]
    4 id: '0' .  [$end]

    $end      reduce using rule 3 (num)
    $end      [reduce using rule 4 (id)]
    $default  reduce using rule 3 (num)


state 2

    0 $accept: exp . $end

    $end  shift, and go to state 5


state 3

    1 exp: num .

    $default  reduce using rule 1 (exp)


state 4

    2 exp: id .

    $default  reduce using rule 2 (exp)


state 5

    0 $accept: exp $end .

    $default  accept
]])

AT_CLEANUP




## -------------------- ##
## %expect not enough.  ##
## -------------------- ##

AT_SETUP([%expect not enough])

AT_DATA([input.y],
[[%token NUM OP
%expect 0
%%
exp: exp OP exp | NUM;
]])

AT_BISON_CHECK([-o input.c input.y], 1, [],
[input.y: conflicts: 1 shift/reduce
input.y: expected 0 shift/reduce conflicts
])
AT_CLEANUP


## --------------- ##
## %expect right.  ##
## --------------- ##

AT_SETUP([%expect right])

AT_DATA([input.y],
[[%token NUM OP
%expect 1
%%
exp: exp OP exp | NUM;
]])

AT_BISON_CHECK([-o input.c input.y])
AT_CLEANUP


## ------------------ ##
## %expect too much.  ##
## ------------------ ##

AT_SETUP([%expect too much])

AT_DATA([input.y],
[[%token NUM OP
%expect 2
%%
exp: exp OP exp | NUM;
]])

AT_BISON_CHECK([-o input.c input.y], 1, [],
[input.y: conflicts: 1 shift/reduce
input.y: expected 2 shift/reduce conflicts
])
AT_CLEANUP


## ------------------------------- ##
## %expect with reduce conflicts.  ##
## ------------------------------- ##

AT_SETUP([%expect with reduce conflicts])

AT_DATA([input.y],
[[%expect 0
%%
program: a 'a' | a a;
a: 'a';
]])

AT_BISON_CHECK([-o input.c input.y], 1, [],
[input.y: conflicts: 1 reduce/reduce
input.y: expected 0 reduce/reduce conflicts
])
AT_CLEANUP


## ------------------------- ##
## %prec with user strings.  ##
## ------------------------- ##

AT_SETUP([%prec with user string])

AT_DATA([[input.y]],
[[%%
exp:
  "foo" %prec "foo"
;
]])

AT_BISON_CHECK([-o input.c input.y])
AT_CLEANUP


## -------------------------------- ##
## %no-default-prec without %prec.  ##
## -------------------------------- ##

AT_SETUP([%no-default-prec without %prec])

AT_DATA([[input.y]],
[[%left '+'
%left '*'

%%

%no-default-prec;

e:   e '+' e
   | e '*' e
   | '0'
   ;
]])

AT_BISON_CHECK([-o input.c input.y], 0, [],
[[input.y: conflicts: 4 shift/reduce
]])
AT_CLEANUP


## ----------------------------- ##
## %no-default-prec with %prec.  ##
## ----------------------------- ##

AT_SETUP([%no-default-prec with %prec])

AT_DATA([[input.y]],
[[%left '+'
%left '*'

%%

%no-default-prec;

e:   e '+' e %prec '+'
   | e '*' e %prec '*'
   | '0'
   ;
]])

AT_BISON_CHECK([-o input.c input.y])
AT_CLEANUP


## --------------- ##
## %default-prec.  ##
## --------------- ##

AT_SETUP([%default-prec])

AT_DATA([[input.y]],
[[%left '+'
%left '*'

%%

%default-prec;

e:   e '+' e
   | e '*' e
   | '0'
   ;
]])

AT_BISON_CHECK([-o input.c input.y])
AT_CLEANUP


## ---------------------------------------------- ##
## Unreachable States After Conflict Resolution.  ##
## ---------------------------------------------- ##

AT_SETUP([[Unreachable States After Conflict Resolution]])

# If conflict resolution makes states unreachable, remove those states, report
# rules that are then unused, and don't report conflicts in those states.  Test
# what happens when a nonterminal becomes useless as a result of state removal
# since that causes lalr.o's goto map to be rewritten.

AT_DATA([[input.y]],
[[%output "input.c"
%left 'a'

%%

start: resolved_conflict 'a' reported_conflicts 'a' ;

/* S/R conflict resolved as reduce, so the state with item
 * (resolved_conflict: 'a' . unreachable1) and all it transition successors are
 * unreachable, and the associated production is useless.  */
resolved_conflict:
    'a' unreachable1
  | %prec 'a'
  ;

/* S/R conflict that need not be reported since it is unreachable because of
 * the previous conflict resolution.  Nonterminal unreachable1 and all its
 * productions are useless.  */
unreachable1:
    'a' unreachable2
  |
  ;

/* Likewise for a R/R conflict and nonterminal unreachable2.  */
unreachable2: | ;

/* Make sure remaining S/R and R/R conflicts are still reported correctly even
 * when their states are renumbered due to state removal.  */
reported_conflicts:
    'a'
  | 'a'
  |
  ;

]])

AT_BISON_CHECK([[--report=all input.y]], 0, [],
[[input.y: conflicts: 1 shift/reduce, 1 reduce/reduce
input.y:12.5-20: warning: rule useless in parser due to conflicts: resolved_conflict: 'a' unreachable1
input.y:20.5-20: warning: rule useless in parser due to conflicts: unreachable1: 'a' unreachable2
input.y:21.4: warning: rule useless in parser due to conflicts: unreachable1: /* empty */
input.y:25.13: warning: rule useless in parser due to conflicts: unreachable2: /* empty */
input.y:25.16: warning: rule useless in parser due to conflicts: unreachable2: /* empty */
input.y:31.5-7: warning: rule useless in parser due to conflicts: reported_conflicts: 'a'
input.y:32.4: warning: rule useless in parser due to conflicts: reported_conflicts: /* empty */
]])

AT_CHECK([[cat input.output]], 0,
[[Rules useless in parser due to conflicts

    2 resolved_conflict: 'a' unreachable1

    4 unreachable1: 'a' unreachable2
    5             | /* empty */

    6 unreachable2: /* empty */
    7             | /* empty */

    9 reported_conflicts: 'a'
   10                   | /* empty */


State 4 conflicts: 1 shift/reduce
State 5 conflicts: 1 reduce/reduce


Grammar

    0 $accept: start $end

    1 start: resolved_conflict 'a' reported_conflicts 'a'

    2 resolved_conflict: 'a' unreachable1
    3                  | /* empty */

    4 unreachable1: 'a' unreachable2
    5             | /* empty */

    6 unreachable2: /* empty */
    7             | /* empty */

    8 reported_conflicts: 'a'
    9                   | 'a'
   10                   | /* empty */


Terminals, with rules where they appear

$end (0) 0
'a' (97) 1 2 4 8 9
error (256)


Nonterminals, with rules where they appear

$accept (4)
    on left: 0
start (5)
    on left: 1, on right: 0
resolved_conflict (6)
    on left: 2 3, on right: 1
unreachable1 (7)
    on left: 4 5, on right: 2
unreachable2 (8)
    on left: 6 7, on right: 4
reported_conflicts (9)
    on left: 8 9 10, on right: 1


state 0

    0 $accept: . start $end
    1 start: . resolved_conflict 'a' reported_conflicts 'a'
    2 resolved_conflict: . 'a' unreachable1
    3                  | .  ['a']

    $default  reduce using rule 3 (resolved_conflict)

    start              go to state 1
    resolved_conflict  go to state 2

    Conflict between rule 3 and token 'a' resolved as reduce (%left 'a').


state 1

    0 $accept: start . $end

    $end  shift, and go to state 3


state 2

    1 start: resolved_conflict . 'a' reported_conflicts 'a'

    'a'  shift, and go to state 4


state 3

    0 $accept: start $end .

    $default  accept


state 4

    1 start: resolved_conflict 'a' . reported_conflicts 'a'
    8 reported_conflicts: . 'a'
    9                   | . 'a'
   10                   | .  ['a']

    'a'  shift, and go to state 5

    'a'  [reduce using rule 10 (reported_conflicts)]

    reported_conflicts  go to state 6


state 5

    8 reported_conflicts: 'a' .  ['a']
    9                   | 'a' .  ['a']

    'a'       reduce using rule 8 (reported_conflicts)
    'a'       [reduce using rule 9 (reported_conflicts)]
    $default  reduce using rule 8 (reported_conflicts)


state 6

    1 start: resolved_conflict 'a' reported_conflicts . 'a'

    'a'  shift, and go to state 7


state 7

    1 start: resolved_conflict 'a' reported_conflicts 'a' .

    $default  reduce using rule 1 (start)
]])

AT_DATA([[input-keep.y]],
[[%define lr.keep-unreachable-states
]])
AT_CHECK([[cat input.y >> input-keep.y]])

AT_BISON_CHECK([[input-keep.y]], 0, [],
[[input-keep.y: conflicts: 2 shift/reduce, 2 reduce/reduce
input-keep.y:22.4: warning: rule useless in parser due to conflicts: unreachable1: /* empty */
input-keep.y:26.16: warning: rule useless in parser due to conflicts: unreachable2: /* empty */
input-keep.y:32.5-7: warning: rule useless in parser due to conflicts: reported_conflicts: 'a'
input-keep.y:33.4: warning: rule useless in parser due to conflicts: reported_conflicts: /* empty */
]])

AT_CLEANUP


## ------------------------------------------------------------ ##
## Solved conflicts report for multiple reductions in a state.  ##
## ------------------------------------------------------------ ##

AT_SETUP([[Solved conflicts report for multiple reductions in a state]])

# Used to lose earlier solved conflict messages even within a single S/R/R.

AT_DATA([[input.y]],
[[%left 'a'
%right 'b'
%right 'c'
%right 'd'
%%
start:
    'a'
  | empty_a 'a'
  | 'b'
  | empty_b 'b'
  | 'c'
  | empty_c1 'c'
  | empty_c2 'c'
  | empty_c3 'c'
  ;
empty_a: %prec 'a' ;
empty_b: %prec 'b' ;
empty_c1: %prec 'c' ;
empty_c2: %prec 'c' ;
empty_c3: %prec 'd' ;
]])
AT_BISON_CHECK([[--report=all -o input.c input.y]], 0, [], [ignore])
AT_CHECK([[cat input.output | sed -n '/^state 0$/,/^state 1$/p']], 0,
[[state 0

    0 $accept: . start $end
    1 start: . 'a'
    2      | . empty_a 'a'
    3      | . 'b'
    4      | . empty_b 'b'
    5      | . 'c'
    6      | . empty_c1 'c'
    7      | . empty_c2 'c'
    8      | . empty_c3 'c'
    9 empty_a: .  ['a']
   10 empty_b: .  []
   11 empty_c1: .  []
   12 empty_c2: .  []
   13 empty_c3: .  ['c']

    'b'  shift, and go to state 1
 
    'c'       reduce using rule 13 (empty_c3)
    $default  reduce using rule 9 (empty_a)

    start     go to state 2
    empty_a   go to state 3
    empty_b   go to state 4
    empty_c1  go to state 5
    empty_c2  go to state 6
    empty_c3  go to state 7

    Conflict between rule 9 and token 'a' resolved as reduce (%left 'a').
    Conflict between rule 10 and token 'b' resolved as shift (%right 'b').
    Conflict between rule 11 and token 'c' resolved as shift (%right 'c').
    Conflict between rule 12 and token 'c' resolved as shift (%right 'c').
    Conflict between rule 13 and token 'c' resolved as reduce ('c' < 'd').


state 1
]])

AT_CLEANUP


## ------------------------------------------------------------ ##
## %nonassoc error actions for multiple reductions in a state.  ##
## ------------------------------------------------------------ ##

# Used to abort when trying to resolve conflicts as %nonassoc error actions for
# multiple reductions in a state.

# For a %nonassoc error action token, used to print the first remaining
# reduction on that token without brackets.

AT_SETUP([[%nonassoc error actions for multiple reductions in a state]])

AT_DATA([[input.y]],
[[%nonassoc 'a' 'b' 'c'
%%
start:
    'a'
  | empty_a 'a'
  | 'b'
  | empty_b 'b'
  | 'c'
  | empty_c1 'c'
  | empty_c2 'c'
  | empty_c3 'c'
  ;
empty_a: %prec 'a' ;
empty_b: %prec 'b' ;
empty_c1: %prec 'c' ;
empty_c2: %prec 'c' ;
empty_c3: %prec 'c' ;
]])

AT_BISON_CHECK([[--report=all -o input.c input.y]], 0, [], [ignore])
AT_CHECK([[cat input.output | sed -n '/^state 0$/,/^state 1$/p']], 0,
[[state 0

    0 $accept: . start $end
    1 start: . 'a'
    2      | . empty_a 'a'
    3      | . 'b'
    4      | . empty_b 'b'
    5      | . 'c'
    6      | . empty_c1 'c'
    7      | . empty_c2 'c'
    8      | . empty_c3 'c'
    9 empty_a: .  []
   10 empty_b: .  []
   11 empty_c1: .  []
   12 empty_c2: .  ['c']
   13 empty_c3: .  ['c']

    'a'  error (nonassociative)
    'b'  error (nonassociative)
    'c'  error (nonassociative)

    'c'  [reduce using rule 12 (empty_c2)]
    'c'  [reduce using rule 13 (empty_c3)]

    start     go to state 1
    empty_a   go to state 2
    empty_b   go to state 3
    empty_c1  go to state 4
    empty_c2  go to state 5
    empty_c3  go to state 6

    Conflict between rule 9 and token 'a' resolved as an error (%nonassoc 'a').
    Conflict between rule 10 and token 'b' resolved as an error (%nonassoc 'b').
    Conflict between rule 11 and token 'c' resolved as an error (%nonassoc 'c').


state 1
]])
AT_CLEANUP