tests/conflicts.at

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

# Copyright (C) 2002-2005, 2007-2015, 2018-2022 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 <https://www.gnu.org/licenses/>.

AT_BANNER([[Conflicts.]])

## ------------------------- ##
## Token declaration order.  ##
## ------------------------- ##

# This test checks that token are declared left to right when in a precedence
# statement.

AT_SETUP([Token declaration order])

AT_BISON_OPTION_PUSHDEFS

AT_DATA_GRAMMAR([[input.y]],
[[%code {
  #include <stdio.h>
  ]AT_YYERROR_DECLARE[
  ]AT_YYLEX_DECLARE[
}
%token A B C
%token D
%right E F G
%right H I
%right J
%left  K
%left  L M N
%nonassoc O P Q
%precedence R S T U
%precedence V W
%%
exp: A
%%
]AT_YYERROR_DEFINE[
]AT_YYLEX_DEFINE[
int main (void)
{
  assert (A < B);
  assert (B < C);
  assert (C < D);
  assert (D < E);
  assert (E < F);
  assert (F < G);
  assert (G < H);
  assert (H < I);
  assert (I < J);
  assert (J < K);
  assert (K < L);
  assert (L < M);
  assert (M < N);
  assert (N < O);
  assert (O < P);
  assert (P < Q);
  assert (Q < R);
  assert (R < S);
  assert (S < T);
  assert (T < U);
  assert (U < V);
  assert (V < W);
  return 0;
}
]])

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

AT_PARSER_CHECK([input])

AT_BISON_OPTION_POPDEFS

AT_CLEANUP


## --------------------------------------------------- ##
## Token declaration order: literals vs. identifiers.  ##
## --------------------------------------------------- ##

# This test checks that when several tokens are declared by the same keyword,
# some of them defined as a character ('a'), others as simple textual reference
# (A), they are declared correctly left to right.
# Previously, the following test would declare the states in the order 'o' 'p'
# M N, instead of M N 'o' 'p'.

AT_SETUP([Token declaration order: literals vs. identifiers])

AT_BISON_OPTION_PUSHDEFS
AT_DATA_GRAMMAR([[input.y]],
[[%token 'a' 'b' C D
%token E F 'g' 'h'
%right 'i' 'j' K L
%right M N 'o' 'p'
%%
exp: 'a'
   | 'b'
   | C
   | D
   | E
   | F
   | 'g'
   | 'h'
   | 'i'
   | 'j'
   | K
   | L
   | M
   | N
   | 'o'
   | 'p'
;
%%
]])

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: . exp $end
    1 exp: . 'a'
    2    | . 'b'
    3    | . C
    4    | . D
    5    | . E
    6    | . F
    7    | . 'g'
    8    | . 'h'
    9    | . 'i'
   10    | . 'j'
   11    | . K
   12    | . L
   13    | . M
   14    | . N
   15    | . 'o'
   16    | . 'p'

    'a'  shift, and go to state 1
    'b'  shift, and go to state 2
    C    shift, and go to state 3
    D    shift, and go to state 4
    E    shift, and go to state 5
    F    shift, and go to state 6
    'g'  shift, and go to state 7
    'h'  shift, and go to state 8
    'i'  shift, and go to state 9
    'j'  shift, and go to state 10
    K    shift, and go to state 11
    L    shift, and go to state 12
    M    shift, and go to state 13
    N    shift, and go to state 14
    'o'  shift, and go to state 15
    'p'  shift, and go to state 16

    exp  go to state 17


State 1
]])

AT_BISON_OPTION_POPDEFS
AT_CLEANUP


## ------------------------------- ##
## Useless associativity warning.  ##
## ------------------------------- ##

AT_SETUP([Useless associativity warning])

AT_DATA([[input.y]],
[[%token EQ "=" PL "+" ST "*"  LP "("
%nonassoc "="
%left "+"
%left "*"
%precedence "("
%%
stmt:
  exp
| "var" "=" exp
;

exp:
  exp "+" exp
| exp "*" "num"
| "(" exp ")"
| "num"
;
]])

AT_BISON_CHECK([-Wprecedence input.y], 0, [],
[[input.y:2.1-9: warning: useless precedence and associativity for "=" [-Wprecedence]
input.y:4.1-5: warning: useless associativity for "*", use %precedence [-Wprecedence]
input.y:5.1-11: warning: useless precedence for "(" [-Wprecedence]
]])

AT_CLEANUP


## ---------------------------- ##
## Useless precedence warning.  ##
## ---------------------------- ##

AT_SETUP([Useless precedence warning])

AT_DATA([[input.y]],
[[%token A B U V W X Y Z
%precedence Z
%left X
%precedence Y
%left W
%right V
%nonassoc U
%%
a: b
 | a U b
 | f
;
b: c
 | b V c
;
c: d
 | c W d
;
d: A
 | d X d
 | d Y A
;
f: B
 | f Z B
;
]])

AT_BISON_CHECK([-Wprecedence -fcaret -o input.c input.y], 0, [],
[[input.y:7.1-9: warning: useless precedence and associativity for U [-Wprecedence]
    7 | %nonassoc U
      | ^~~~~~~~~
input.y:6.1-6: warning: useless precedence and associativity for V [-Wprecedence]
    6 | %right V
      | ^~~~~~
input.y:5.1-5: warning: useless precedence and associativity for W [-Wprecedence]
    5 | %left W
      | ^~~~~
input.y:2.1-11: warning: useless precedence for Z [-Wprecedence]
    2 | %precedence Z
      | ^~~~~~~~~~~
]])

AT_CLEANUP


## ---------------- ##
## 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' | %empty;
]])

AT_BISON_CHECK([-o input.c input.y], 0, [],
[[input.y:4.10-15: warning: rule useless in parser due to conflicts [-Wother]
]])

AT_BISON_CHECK([-fcaret -o input.c input.y], 0, [],
[[input.y:4.10-15: warning: rule useless in parser due to conflicts [-Wother]
    4 | e: 'e' | %empty;
      |          ^~~~~~
]])

AT_CLEANUP


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

AT_SETUP([%nonassoc and eof])

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

]AT_YYERROR_DEFINE[
/* The current argument. */
static const char *input;

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

%}

%define parse.error verbose

%nonassoc '<' '>'

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

m4_pushdef([AT_NONASSOC_AND_EOF_CHECK],
[AT_BISON_CHECK([$1[ -o input.c input.y]])
AT_COMPILE([input])

m4_pushdef([AT_EXPECTING], [m4_if($2, [correct], [[, expecting end of file]])])

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

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

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

m4_popdef([AT_EXPECTING])])

# Expected token list is missing.
AT_NONASSOC_AND_EOF_CHECK([], [[incorrect]])

# We must disable default reductions in inconsistent states in order to
# have an explicit list of all expected tokens.
AT_NONASSOC_AND_EOF_CHECK([[-Dlr.default-reduction=consistent]],
                          [[correct]])

# lr.default-reduction=consistent happens to work for this test case.
# However, for other grammars, lookahead sets can be merged for
# different left contexts, so it is still possible to have an incorrect
# expected list.  Canonical LR is almost a general solution (that is, it
# can fail only when %nonassoc is used), so make sure it gives the same
# result as above.
AT_NONASSOC_AND_EOF_CHECK([[-Dlr.type=canonical-lr]], [[correct]])

# parse.lac=full is a completely general solution that does not require
# any of the above sacrifices.  Of course, it does not extend the
# language-recognition power of LALR to (IE)LR, but it does ensure that
# the reported list of expected tokens matches what the given parser
# would have accepted in place of the unexpected token.
AT_NONASSOC_AND_EOF_CHECK([[-Dparse.lac=full]], [[correct]])

m4_popdef([AT_NONASSOC_AND_EOF_CHECK])

AT_CLEANUP



## ------------------------------------------- ##
## parse.error=verbose and consistent errors.  ##
## ------------------------------------------- ##

AT_CONSISTENT_ERRORS_CHECK([BISON-DIRECTIVE],
                           [GRAMMAR],
                           [INPUT],
                           [UNEXPECTED-TOKEN], [EXPECTED-TOKEN])
m4_pushdef([AT_CONSISTENT_ERRORS_CHECK], [

AT_SETUP([[parse.error=verbose and consistent errors: ]$1])

AT_BISON_OPTION_PUSHDEFS([$1 AT_CXX_IF([[%header]], [[%define api.pure]])])

AT_DATA_GRAMMAR([input.y],
[AT_JAVA_IF([[

%code imports {
  import java.io.IOException;
}]], [[

%code {
  #include <assert.h>
  ]AT_YYERROR_DECLARE[
  ]AT_YYLEX_DECLARE[
  #define USE(Var)
}

]AT_CXX_IF([[%header]], [[%define api.pure]])])[

]AT_YACC_C_IF([[
%code {
  #if defined __GNUC__ && 8 <= __GNUC__
  # pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
  #endif
}
]])[

]$1[

%define parse.error verbose

%%

]$2[

]AT_JAVA_IF([[%code lexer {
  ]AT_YYLEX_DEFINE(["$3"], [[return new Integer(1)]])[
  ]AT_YYERROR_DEFINE[
};
%%
]], [[
%%
]AT_YYLEX_DEFINE(["$3"], [[*lvalp = 1]])[
]AT_YYERROR_DEFINE[
]])[

/*-------.
| main.  |
`-------*/
]AT_MAIN_DEFINE
])

AT_FULL_COMPILE([[input]])

m4_pushdef([AT_EXPECTING], [m4_if($5, [ab], [[, expecting 'a' or 'b']],
                                  $5, [a],  [[, expecting 'a']],
                                  $5, [b],  [[, expecting 'b']])])

AT_PARSER_CHECK([[input]], [[1]],
[[]],
[[syntax error, unexpected ]$4[]AT_EXPECTING[
]])

m4_popdef([AT_EXPECTING])
AT_BISON_OPTION_POPDEFS

AT_CLEANUP
]) dnl AT_CONSISTENT_ERRORS_CHECK




m4_pushdef([AT_PREVIOUS_STATE_GRAMMAR],
[[%nonassoc 'a';

start: consistent-error-on-a-a 'a' ;

consistent-error-on-a-a:
    'a' default-reduction
  | 'a' default-reduction 'a'
  | 'a' shift
  ;

default-reduction: %empty ;
shift: 'b' ;

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

m4_pushdef([AT_PREVIOUS_STATE_INPUT], [[a]])

# Unfortunately, no expected tokens are reported even though 'b' can be
# accepted.  Nevertheless, the main point of this test is to make sure
# that at least the unexpected token is reported.  In a previous version
# of Bison, it wasn't reported because the error is detected in a
# consistent state with an error action, and that case always triggered
# the simple "syntax error" message.
#
# The point isn't to test IELR here, but state merging happens to
# complicate this example.
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type ielr]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[none]])
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type ielr
                             %glr-parser]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[none]])
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type ielr
                             %language "c++"]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[none]])
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type ielr
                             %language "java"]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[none]])

# Even canonical LR doesn't foresee the error for 'a'!
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type ielr
                             %define lr.default-reduction consistent]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[ab]])
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type ielr
                             %define lr.default-reduction accepting]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[ab]])
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type canonical-lr]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[ab]])

# Only LAC gets it right.  In C.
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type canonical-lr
                             %define parse.lac full]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[b]])
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type ielr
                             %define parse.lac full]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[b]])

# Only LAC gets it right.  In C++.
AT_CONSISTENT_ERRORS_CHECK([[%language "c++"
                             %define lr.type canonical-lr
                             %define parse.lac full]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[b]])
AT_CONSISTENT_ERRORS_CHECK([[%language "c++"
                             %define lr.type ielr
                             %define parse.lac full]],
                           [AT_PREVIOUS_STATE_GRAMMAR],
                           [AT_PREVIOUS_STATE_INPUT],
                           [[end of file]], [[b]])

m4_popdef([AT_PREVIOUS_STATE_GRAMMAR])
m4_popdef([AT_PREVIOUS_STATE_INPUT])

m4_pushdef([AT_USER_ACTION_GRAMMAR],
[[%nonassoc 'a';

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

// Rather than depend on an inconsistent state to induce reading a
// lookahead as in the previous grammar, just assign the lookahead in a
// semantic action.  That lookahead 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 the bug described in the previous grammar, the
// unexpected token was not reported at all.
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' ;
]])
m4_pushdef([AT_USER_ACTION_INPUT], [[aa]])

AT_CONSISTENT_ERRORS_CHECK([[]],
                           [AT_USER_ACTION_GRAMMAR],
                           [AT_USER_ACTION_INPUT],
                           [['b']], [[none]])
AT_CONSISTENT_ERRORS_CHECK([[%glr-parser]],
                           [AT_USER_ACTION_GRAMMAR],
                           [AT_USER_ACTION_INPUT],
                           [['b']], [[none]])
# No C++ or Java test because yychar cannot be manipulated by users.

AT_CONSISTENT_ERRORS_CHECK([[%define lr.default-reduction consistent]],
                           [AT_USER_ACTION_GRAMMAR],
                           [AT_USER_ACTION_INPUT],
                           [['b']], [[none]])

# Canonical LR doesn't foresee the error for 'a'!
AT_CONSISTENT_ERRORS_CHECK([[%define lr.default-reduction accepting]],
                           [AT_USER_ACTION_GRAMMAR],
                           [AT_USER_ACTION_INPUT],
                           [[end of file]], [[a]])
AT_CONSISTENT_ERRORS_CHECK([[%define lr.type canonical-lr]],
                           [AT_USER_ACTION_GRAMMAR],
                           [AT_USER_ACTION_INPUT],
                           [[end of file]], [[a]])

AT_CONSISTENT_ERRORS_CHECK([[%define parse.lac full]],
                           [AT_USER_ACTION_GRAMMAR],
                           [AT_USER_ACTION_INPUT],
                           [['b']], [[none]])
AT_CONSISTENT_ERRORS_CHECK([[%define parse.lac full
                             %define lr.default-reduction accepting]],
                           [AT_USER_ACTION_GRAMMAR],
                           [AT_USER_ACTION_INPUT],
                           [[end of file]], [[none]])

m4_popdef([AT_USER_ACTION_GRAMMAR])
m4_popdef([AT_USER_ACTION_INPUT])

m4_popdef([AT_CONSISTENT_ERRORS_CHECK])




## ------------------------------------------------------- ##
## LAC: %nonassoc requires splitting canonical LR states.  ##
## ------------------------------------------------------- ##

# This test case demonstrates that, when %nonassoc is used, canonical
# LR(1) parser table construction followed by conflict resolution
# without further state splitting is not always sufficient to produce a
# parser that can detect all syntax errors as soon as possible on one
# token of lookahead.  However, LAC solves the problem completely even
# with minimal LR parser tables.

AT_SETUP([[LAC: %nonassoc requires splitting canonical LR states]])
AT_BISON_OPTION_PUSHDEFS
AT_DATA_GRAMMAR([[input.y]],
[[%code {
  #include <stdio.h>
  ]AT_YYERROR_DECLARE[
  ]AT_YYLEX_DECLARE[
}

%define parse.error verbose
%nonassoc 'a'

%%

start:
  'a' problem 'a' // First context.
| 'b' problem 'b' // Second context.
| 'c' reduce-nonassoc // Just makes reduce-nonassoc useful.
;

problem:
  look reduce-nonassoc
| look 'a'
| look 'b'
;

// For the state reached after shifting the 'a' in these productions,
// lookahead sets are the same in both the first and second contexts.
// Thus, canonical LR reuses the same state for both contexts.  However,
// the lookahead 'a' for the reduction "look: 'a'" later becomes an
// error action only in the first context.  In order to immediately
// detect the syntax error on 'a' here for only the first context, this
// canonical LR state would have to be split into two states, and the
// 'a' lookahead would have to be removed from only one of the states.
look:
  'a' // Reduction lookahead set is always ['a', 'b'].
| 'a' 'b'
| 'a' 'c' // 'c' is forgotten as an expected token.
;

reduce-nonassoc: %prec 'a';

%%
]AT_YYERROR_DEFINE[
]AT_YYLEX_DEFINE(["aaa"])[
]AT_MAIN_DEFINE
])
AT_BISON_OPTION_POPDEFS

# Show canonical LR's failure.
AT_BISON_CHECK([[-Dlr.type=canonical-lr -o input.c input.y]],
               [[0]], [[]],
[[input.y: warning: 2 shift/reduce conflicts [-Wconflicts-sr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])
AT_COMPILE([[input]])
AT_PARSER_CHECK([[input]], [[1]], [[]],
[[syntax error, unexpected 'a', expecting 'b'
]])

# It's corrected by LAC.
AT_BISON_CHECK([[-Dlr.type=canonical-lr -Dparse.lac=full \
                 -o input.c input.y]], [[0]], [[]],
[[input.y: warning: 2 shift/reduce conflicts [-Wconflicts-sr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])
AT_COMPILE([[input]])
AT_PARSER_CHECK([[input]], [[1]], [[]],
[[syntax error, unexpected 'a', expecting 'b' or 'c'
]])

# IELR is sufficient when LAC is used.
AT_BISON_CHECK([[-Dlr.type=ielr -Dparse.lac=full -o input.c input.y]],
               [[0]], [[]],
[[input.y: warning: 2 shift/reduce conflicts [-Wconflicts-sr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])
AT_COMPILE([[input]])
AT_PARSER_CHECK([[input]], [[1]], [[]],
[[syntax error, unexpected 'a', expecting 'b' or 'c'
]])

AT_CLEANUP

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

AT_SETUP([Unresolved SR Conflicts])

AT_KEYWORDS([cex 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: warning: 1 shift/reduce conflict [-Wconflicts-sr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])

# 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)

    shift/reduce conflict on token OP:
        1 exp: exp OP exp .
        1 exp: exp . OP exp
      Example: exp OP exp . OP exp
      Shift derivation
        exp
        `-> 1: exp OP exp
                      `-> 1: exp . OP exp
      Reduce derivation
        exp
        `-> 1: exp                 OP exp
               `-> 1: exp OP 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


## ---------------------- ##
## %precedence suffices.  ##
## ---------------------- ##

AT_SETUP([%precedence suffices])

AT_DATA([input.y],
[[%precedence "then"
%precedence "else"
%%
stmt:
  "if" cond "then" stmt
| "if" cond "then" stmt "else" stmt
| "stmt"
;

cond:
  "exp"
;
]])

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

AT_CLEANUP


## ------------------------------ ##
## %precedence does not suffice.  ##
## ------------------------------ ##

AT_SETUP([%precedence does not suffice])

AT_DATA([input.y],
[[%precedence "then"
%precedence "else"
%%
stmt:
  "if" cond "then" stmt
| "if" cond "then" stmt "else" stmt
| "stmt"
;

cond:
  "exp"
| cond "then" cond
;
]])

AT_BISON_CHECK([-o input.c input.y], 0, [],
[[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
input.y:12.3-18: warning: rule useless in parser due to conflicts [-Wother]
]])

AT_CLEANUP


## ---------------------------------------- ##
## Syntax error in consistent error state.  ##
## ---------------------------------------- ##

# AT_TEST(SKELETON-NAME)
# ----------------------
# Make sure yysyntax_error does nothing silly when called on yytoken
# == YYEMPTY.

m4_pushdef([AT_TEST],
[AT_SETUP([Syntax error in consistent error state: $1])

AT_BISON_OPTION_PUSHDEFS([%skeleton "$1"])

AT_DATA_GRAMMAR([input.y],
[[%define parse.error verbose
%skeleton "$1"
%%
%nonassoc 'a';

start: 'a' consistent-error-on-a-a 'a';

consistent-error-on-a-a:
    'a' default-reduction
  | 'a' default-reduction 'a'
  ;

default-reduction: %empty;

%code {
  #include <stdio.h>
  ]AT_YYERROR_DECLARE[
  ]AT_YYLEX_DECLARE[
};
%%
]AT_YYERROR_DEFINE[
]AT_YYLEX_DEFINE("aa")[
]AT_MAIN_DEFINE[
]])

AT_BISON_CHECK([-o input.AT_LANG_EXT input.y], 0, [],
[[input.y:17.5-25: warning: rule useless in parser due to conflicts [-Wother]
input.y:18.5-29: warning: rule useless in parser due to conflicts [-Wother]
]])
AT_LANG_COMPILE([input])
AT_PARSER_CHECK([[input]], 1, [],
[[syntax error
]])

AT_BISON_OPTION_POPDEFS
AT_CLEANUP
])

## FIXME: test Java and D.
m4_map_args([AT_TEST], [yacc.c], [glr.c], [lalr1.cc], [glr.cc], [glr2.cc])

m4_popdef([AT_TEST])



## -------------------------------- ##
## 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([cex 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: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
input.y:4.6-8: warning: rule useless in parser due to conflicts [-Wother]
]])

# 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)

    reduce/reduce conflict on token $end:
        3 num: '0' .
        4 id: '0' .
      Example: '0' .
      First reduce derivation
        exp
        `-> 1: num
               `-> 3: '0' .
      Second reduce derivation
        exp
        `-> 2: id
               `-> 4: '0' .



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: error: shift/reduce conflicts: 1 found, 0 expected
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])
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: error: shift/reduce conflicts: 1 found, 2 expected
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])
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: error: reduce/reduce conflicts: 1 found, 0 expected
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])
AT_CLEANUP


## ------------------------------------ ##
## %expect in grammar rule not enough.  ##
## ------------------------------------ ##

AT_SETUP([%expect in grammar rule not enough])

AT_DATA([input.y],
[[%token NUM OP
%expect 1
%%
exp: exp OP exp %expect 0 | NUM;
]])

AT_BISON_CHECK([-o input.c input.y], 1, [],
[[input.y:4.6-25: error: shift/reduce conflicts for rule 1: 1 found, 0 expected
]])
AT_CLEANUP


## ------------------------------- ##
## %expect in grammar rule right.  ##
## ------------------------------- ##

AT_SETUP([%expect in grammar rule right])

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

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.  ##
## ---------------------------------- ##

AT_SETUP([%expect in grammar rule too much])

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

AT_BISON_CHECK([-o input.c input.y], 1, [],
[[input.y:4.19-31: error: shift/reduce conflicts for rule 2: 0 found, 1 expected
]])
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
   12 | 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
   12 | b: %expect-rr 2
      |    ^~~~~~~~~~~~
]])
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([-Wall -o input.c input.y], 0, [],
[[input.y: warning: 4 shift/reduce conflicts [-Wconflicts-sr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
input.y:1.1-5: warning: useless precedence and associativity for '+' [-Wprecedence]
input.y:2.1-5: warning: useless precedence and associativity for '*' [-Wprecedence]
]])
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]])

AT_KEYWORDS([cex report])

# 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: warning: 1 shift/reduce conflict [-Wconflicts-sr]
input.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
input.y:12.5-20: warning: rule useless in parser due to conflicts [-Wother]
input.y:20.5-20: warning: rule useless in parser due to conflicts [-Wother]
input.y:21.4: warning: rule useless in parser due to conflicts [-Wother]
input.y:25.14: warning: rule useless in parser due to conflicts [-Wother]
input.y:25.16: warning: rule useless in parser due to conflicts [-Wother]
input.y:31.5-7: warning: rule useless in parser due to conflicts [-Wother]
input.y:32.4: warning: rule useless in parser due to conflicts [-Wother]
]])

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                  | %empty .  ['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                   | %empty .  ['a']

    'a'  shift, and go to state 5

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

    reported_conflicts  go to state 6

    shift/reduce conflict on token 'a':
       10 reported_conflicts: %empty .
        8 reported_conflicts: . 'a'
      First example: resolved_conflict . 'a' 'a'
      Shift derivation
        start
        `-> 1: resolved_conflict reported_conflicts 'a'
                                 `-> 8: . 'a'
      Second example: resolved_conflict . 'a'
      Reduce derivation
        start
        `-> 1: resolved_conflict reported_conflicts 'a'
                                 `-> 10: %empty .

    shift/reduce conflict on token 'a':
       10 reported_conflicts: %empty .
        9 reported_conflicts: . 'a'
      First example: resolved_conflict . 'a' 'a'
      Shift derivation
        start
        `-> 1: resolved_conflict reported_conflicts 'a'
                                 `-> 9: . 'a'
      Second example: resolved_conflict . 'a'
      Reduce derivation
        start
        `-> 1: resolved_conflict reported_conflicts 'a'
                                 `-> 10: %empty .



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)

    reduce/reduce conflict on token 'a':
        8 reported_conflicts: 'a' .
        9 reported_conflicts: 'a' .
      Example: 'a' .
      First reduce derivation
        reported_conflicts
        `-> 8: 'a' .
      Second reduce derivation
        reported_conflicts
        `-> 9: 'a' .



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-state
]])
AT_CHECK([[cat input.y >> input-keep.y]])

AT_BISON_CHECK([[input-keep.y]], 0, [],
[[input-keep.y: warning: 2 shift/reduce conflicts [-Wconflicts-sr]
input-keep.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr]
input-keep.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
input-keep.y:22.4: warning: rule useless in parser due to conflicts [-Wother]
input-keep.y:26.16: warning: rule useless in parser due to conflicts [-Wother]
input-keep.y:32.5-7: warning: rule useless in parser due to conflicts [-Wother]
input-keep.y:33.4: warning: rule useless in parser due to conflicts [-Wother]
]])

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:  %empty %prec 'a' ;
empty_b:  %empty %prec 'b' ;
empty_c1: %empty %prec 'c' ;
empty_c2: %empty %prec 'c' ;
empty_c3: %empty %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: %empty .  ['a']
   10 empty_b: %empty .  []
   11 empty_c1: %empty .  []
   12 empty_c2: %empty .  []
   13 empty_c3: %empty .  ['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_KEYWORDS([cex report])

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([[--trace=cex -fcaret --report=all -o input.c input.y]], 0, [],
[[bison (GNU Bison) ]AT_PACKAGE_VERSION[
init: 0.000000
# state items: 26
State 0:
    0 $accept: . start $end
    ->     0 $accept: start . $end
    =>     2 start: . empty_a 'a'
    =>     4 start: . empty_b 'b'
    =>     6 start: . empty_c1 'c'
    =>     7 start: . empty_c2 'c'
    =>     8 start: . empty_c3 'c'

    1 start: . 'a'  DISABLED

    2 start: . empty_a 'a'
    ->     2 start: empty_a . 'a'
    =>     9 empty_a: %empty .
    <-     0 $accept: . start $end

    3 start: . 'b'  DISABLED

    4 start: . empty_b 'b'
    ->     4 start: empty_b . 'b'
    =>    10 empty_b: %empty .
    <-     0 $accept: . start $end

    5 start: . 'c'  DISABLED

    6 start: . empty_c1 'c'
    ->     6 start: empty_c1 . 'c'
    =>    11 empty_c1: %empty .
    <-     0 $accept: . start $end

    7 start: . empty_c2 'c'
    ->     7 start: empty_c2 . 'c'
    =>    12 empty_c2: %empty .
    <-     0 $accept: . start $end

    8 start: . empty_c3 'c'
    ->     8 start: empty_c3 . 'c'
    =>    13 empty_c3: %empty .
    <-     0 $accept: . start $end

    9 empty_a: %empty .
    <-     2 start: . empty_a 'a'

   10 empty_b: %empty .
    <-     4 start: . empty_b 'b'

   11 empty_c1: %empty .
    <-     6 start: . empty_c1 'c'

   12 empty_c2: %empty .
    <-     7 start: . empty_c2 'c'

   13 empty_c3: %empty .
    <-     8 start: . empty_c3 'c'

State 1:
    0 $accept: start . $end
    ->     0 $accept: start $end .
    <-     0 $accept: . start $end

State 2:
    2 start: empty_a . 'a'
    ->     2 start: empty_a 'a' .
    <-     2 start: . empty_a 'a'

State 3:
    4 start: empty_b . 'b'
    ->     4 start: empty_b 'b' .
    <-     4 start: . empty_b 'b'

State 4:
    6 start: empty_c1 . 'c'
    ->     6 start: empty_c1 'c' .
    <-     6 start: . empty_c1 'c'

State 5:
    7 start: empty_c2 . 'c'
    ->     7 start: empty_c2 'c' .
    <-     7 start: . empty_c2 'c'

State 6:
    8 start: empty_c3 . 'c'
    ->     8 start: empty_c3 'c' .
    <-     8 start: . empty_c3 'c'

State 7:
    0 $accept: start $end .
    <-     0 $accept: start . $end

State 8:
    2 start: empty_a 'a' .
    <-     2 start: empty_a . 'a'

State 9:
    4 start: empty_b 'b' .
    <-     4 start: empty_b . 'b'

State 10:
    6 start: empty_c1 'c' .
    <-     6 start: empty_c1 . 'c'

State 11:
    7 start: empty_c2 'c' .
    <-     7 start: empty_c2 . 'c'

State 12:
    8 start: empty_c3 'c' .
    <-     8 start: empty_c3 . 'c'

FIRSTS
  $accept firsts
    'a'
    'b'
    'c'
  start firsts
    'a'
    'b'
    'c'
  empty_a firsts
  empty_b firsts
  empty_c1 firsts
  empty_c2 firsts
  empty_c3 firsts


input.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
input.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
input.y:4.5-7: warning: rule useless in parser due to conflicts [-Wother]
    4 |     'a'
      |     ^~~
input.y:6.5-7: warning: rule useless in parser due to conflicts [-Wother]
    6 |   | 'b'
      |     ^~~
input.y:8.5-7: warning: rule useless in parser due to conflicts [-Wother]
    8 |   | 'c'
      |     ^~~
input.y:13.10-18: warning: rule useless in parser due to conflicts [-Wother]
   13 | empty_a: %prec 'a' ;
      |          ^~~~~~~~~
input.y:14.10-18: warning: rule useless in parser due to conflicts [-Wother]
   14 | empty_b: %prec 'b' ;
      |          ^~~~~~~~~
input.y:15.11-19: warning: rule useless in parser due to conflicts [-Wother]
   15 | empty_c1: %prec 'c' ;
      |           ^~~~~~~~~
input.y:16.11-19: warning: rule useless in parser due to conflicts [-Wother]
   16 | empty_c2: %prec 'c' ;
      |           ^~~~~~~~~
input.y:17.11-19: warning: rule useless in parser due to conflicts [-Wother]
   17 | empty_c3: %prec 'c' ;
      |           ^~~~~~~~~
REDUCE ITEM PATH:
    0 $accept: . start $end
    7 start: . empty_c2 'c'
   12 empty_c2: %empty .
CONFLICT 1 (size 1 depth 0 rc 2)
   12 empty_c2: %empty .
   12 empty_c2: %empty .

    .

CONFLICT 2 (size 1 depth 0 rc 2)
   13 empty_c3: %empty .
   13 empty_c3: %empty .

    .


CONFLICT 1 (size 2 depth -1 rc 4)
    7 start: . empty_c2 'c'
    7 start: empty_c2 . 'c'

    empty_c2
    `-> 12: %empty .

CONFLICT 2 (size 1 depth 0 rc 3)
   13 empty_c3: %empty .
   13 empty_c3: %empty .

    .


CONFLICT 1 (size 1 depth 0 rc 3)
   12 empty_c2: %empty .
   12 empty_c2: %empty .

    .

CONFLICT 2 (size 2 depth -1 rc 2)
    8 start: . empty_c3 'c'
    8 start: empty_c3 . 'c'

    empty_c3
    `-> 13: %empty .


CONFLICT 1 (size 2 depth -1 rc 3)
    7 start: . empty_c2 'c'
    7 start: empty_c2 . 'c'

    empty_c2
    `-> 12: %empty .

CONFLICT 2 (size 2 depth -1 rc 2)
    8 start: . empty_c3 'c'
    8 start: empty_c3 . 'c'

    empty_c3
    `-> 13: %empty .


CONFLICT 1 (size 3 depth -1 rc 2)
    7 start: . empty_c2 'c'
    7 start: empty_c2 'c' .

    empty_c2
    `-> 12: %empty .

CONFLICT 2 (size 3 depth -1 rc 2)
    8 start: . empty_c3 'c'
    8 start: empty_c3 'c' .

    empty_c3
    `-> 13: %empty .


CONFLICT 1 (size 2 depth -1 rc 4)
    0 $accept: . start $end
    0 $accept: start . $end

    start
    `-> 7: empty_c2         'c'
           `-> 12: %empty .

CONFLICT 2 (size 3 depth -1 rc 3)
    8 start: . empty_c3 'c'
    8 start: empty_c3 'c' .

    empty_c3
    `-> 13: %empty .


CONFLICT 1 (size 3 depth -1 rc 3)
    7 start: . empty_c2 'c'
    7 start: empty_c2 'c' .

    empty_c2
    `-> 12: %empty .

CONFLICT 2 (size 2 depth -1 rc 2)
    0 $accept: . start $end
    0 $accept: start . $end

    start
    `-> 8: empty_c3         'c'
           `-> 13: %empty .


CONFLICT 1 (size 2 depth -1 rc 3)
    0 $accept: . start $end
    0 $accept: start . $end

    start
    `-> 7: empty_c2         'c'
           `-> 12: %empty .

CONFLICT 2 (size 2 depth -1 rc 2)
    0 $accept: . start $end
    0 $accept: start . $end

    start
    `-> 8: empty_c3         'c'
           `-> 13: %empty .


]])
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: %empty .  []
   10 empty_b: %empty .  []
   11 empty_c1: %empty .  []
   12 empty_c2: %empty .  ['c']
   13 empty_c3: %empty .  ['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').

    reduce/reduce conflict on token 'c':
       12 empty_c2: %empty .
       13 empty_c3: %empty .
      Example: . 'c'
      First reduce derivation
        start
        `-> 7: empty_c2         'c'
               `-> 12: %empty .
      Second reduce derivation
        start
        `-> 8: empty_c3         'c'
               `-> 13: %empty .



State 1
]])
AT_CLEANUP


## -------------------- ##
## %expect-rr non GLR.  ##
## -------------------- ##

AT_SETUP([[%expect-rr non GLR]])

AT_DATA([[1.y]],
[[%expect-rr 0
%%
exp: 'a'
]])

AT_BISON_CHECK([[1.y]], [[0]], [],
[[1.y: warning: %expect-rr applies only to GLR parsers [-Wother]
]])

AT_DATA([[2.y]],
[[%expect-rr 1
%%
exp: 'a' | 'a';
]])

AT_BISON_CHECK([[2.y]], [[0]], [],
[[2.y: warning: %expect-rr applies only to GLR parsers [-Wother]
2.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
2.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
2.y:3.12-14: warning: rule useless in parser due to conflicts [-Wother]
]])

AT_CLEANUP


## ---------------------------------- ##
## -W versus %expect and %expect-rr.  ##
## ---------------------------------- ##

AT_SETUP([[-W versus %expect and %expect-rr]])

AT_DATA([[sr-rr.y]],
[[%glr-parser
%%
start: 'a' | A 'a' | B 'a' ;
A: ;
B: ;
]])
AT_DATA([[sr.y]],
[[%glr-parser
%%
start: 'a' | A 'a' ;
A: ;
]])
AT_DATA([[rr.y]],
[[%glr-parser
%%
start: A | B ;
A: ;
B: ;
]])

AT_BISON_CHECK([[sr-rr.y]], [[0]], [[]],
[[sr-rr.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
sr-rr.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
sr-rr.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])
AT_BISON_CHECK([[-Wno-conflicts-sr sr-rr.y]], [[0]], [[]],
[[sr-rr.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
sr-rr.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
]])
AT_BISON_CHECK([[-Wno-conflicts-rr sr-rr.y]], [[0]], [[]],
[[sr-rr.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
]])

[
# This is piece of code is rather complex for a simple task: try every
# combination of (0 or 1 real SR) x (0 or 1 real RR) x (don't %expect
# or %expect 0, 1, or 2 SR) x (don't %expect-rr or %expect-rr 0, 1, or 2
# RR).

# Number and types of genuine conflicts in the grammar.
for gram in sr-rr sr rr; do
  # Number of expected s/r conflicts.
  for sr_exp_i in '' 0 1 2; do
    # Number of expected r/r conflicts.
    for rr_exp_i in '' 0 1 2; do
      test -z "$sr_exp_i" && test -z "$rr_exp_i" && continue

      # Build grammar file.
      sr_exp=0
      rr_exp=0
      file=$gram
      directives=
      if test -n "$sr_exp_i"; then
        sr_exp=$sr_exp_i
        file=$file-expect-$sr_exp
        directives="%expect $sr_exp"
      fi
      if test -n "$rr_exp_i"; then
        rr_exp=$rr_exp_i
        file=$file-expect-rr-$rr_exp
        directives="$directives %expect-rr $rr_exp"
      fi
      file=$file.y
      echo "$directives" > $file
      cat $gram.y >> $file

      # Number of found conflicts.
      case $gram in
        (sr)    sr_count=1; rr_count=0;;
        (rr)    sr_count=0; rr_count=1;;
        (sr-rr) sr_count=1; rr_count=1;;
      esac

      # Update number of expected conflicts: if %expect is given then
      # %expect-rr defaults to 0, and vice-versa.  Leave empty if
      # nothing expected.
      case $sr_exp_i:$rr_exp_i in
        ?:) rr_exp_i=0;;
        :?) sr_exp_i=0;;
      esac

      # Run tests.
      if test $sr_count -eq $sr_exp && test $rr_count -eq $rr_exp; then
        ]AT_BISON_CHECK([[-Wnone $file]])[
        ]AT_BISON_CHECK([[-Werror $file]])[
      else
        {
          issue_note=false
          if test -z "$sr_exp_i" && test "$sr_count" -ne 0; then
            echo "warning: $sr_count shift/reduce conflicts"
            issue_note=true
          elif test "$sr_exp_i" -ne "$sr_count"; then
            echo "error: shift/reduce conflicts: $sr_count found, $sr_exp_i expected"
            if test "$sr_count" -ne 0; then
              issue_note=true
            fi
          fi
          if test -z "$rr_exp_i" && test "$rr_count" -ne 0; then
            echo "warning: $rr_count reduce/reduce conflicts"
            issue_note=true
          elif test "$rr_exp_i" -ne "$rr_count"; then
            echo "error: reduce/reduce conflicts: $rr_count found, $rr_exp_i expected"
            if test "$rr_count" -ne 0; then
              issue_note=true
            fi
          fi
          if $issue_note; then
            echo "note: rerun with option '-Wcounterexamples' to generate conflict counterexamples"
          fi
        } | sed -e "s/^/$file: /" > experr
        ]AT_BISON_CHECK([[-Wnone $file]], [[1]], [[]], [[experr]])[
        ]AT_BISON_CHECK([[-Werror $file]], [[1]], [[]], [[experr]])[
      fi
    done
  done
done]

AT_CLEANUP