Бесполезные правила и нетерминалы в грамматике зубров

У меня есть следующий файл Bison, описывающий мою грамматику языка сценариев:

%error-verbose
%{
#include "node.h"NBlock *programBlock;

#define YYDEBUG 1

extern int yylex();
void yyerror(const char *) { printf("Error: %s\n", s); }
%}

%union {
Node *node;
NBlock *block;
NBody *body;
NHeader *header;
NExpression *expression;
NStatement *statement;
NIdentifier *identifier;
NVariableDeclaration *variableDeclaration;
NDoWhileStatement *doWhileStatement;
NWhileStatement *whileStatement;
NIfStatement *ifStatement;
NForStatement *forStatement;
std::vector<NVariableDeclaration*> *variableDeclarations;
std::vector<NExpression*> *expressions;
std::vector<NStatement*> *statements;
std:string *string;
int token;
}%token <string> TIDENTIFIER TINTEGER TDOUBLE
%token <token> TCEQ TCNE TCLT TCLE TCGT TCGE TEQUAL
%token <token> TLPAREN TRPAREN TLBRACE TRBRACE TCOMMA TDOT
%token <token> TPLUS TMINUS TMUL TDIV TDO TDOUBLE_TYPE TINT_TYPE
%token <token> TELSE TFOR TIF TSEMICOLON TTHEN TWHILE

%type <expression> expression term factor
%type <block> program body header tail statements
%type <statement> statement forStatement ifStatement doWhileStatement whileStatement variableDeclaration
%type <token> comparison
%type <string> identifier_type%left TPLUS TMINUS
%left TMUL TDIV

%start program

%%

program:                TLBRACE body TRBRACE { printf("Reduce body to program\n"); }
;

body:                   header TLBRACE block TRBRACE tail { printf("Reduce header block tail to body\n"); }
;

header:                 TLBRACE variableDeclarations TRBRACE { printf("Reduce variableDeclarations to header\n"); }
| TLBRACE TRBRACE { printf("Reduce empty to header\n"); }
;

variableDeclarations:   variableDeclaration TSEMICOLON { printf("Reduce variable declaration to header\n"); }
| variableDeclarations variableDeclaration TSEMICOLON { printf("Reduce variable declaration list to header\n"); }
;

tail:                   TLBRACE statements TRBRACE { printf("reduce statement list to tail\n"); }
| TLBRACE TRBRACE { printf("Reduce empty to tal\n"); }
;

statements:             statement TSEMICOLON { printf("Reduce statement to statement list\n"); }
| statements statement TSEMICOLON { printf("Reduce statement list to statement list\n"); }
;

statement:              ifStatement { printf("Reduce if to statement\n"); };
| forStatement { printf("Reduce for to statement\n"); };
| doWhileStatement { printf("Reduce doWhile to statement\n"); };
| whileStatement { printf("reduce while to statement\n"); }
| expression { printf("Reduce expression to statement\n"); };
;

forStatement:           TFOR TLPAREN expression TSEMICOLON expression TSEMICOLON expression TRPAREN block { printf("Reduce for to for statement\n"); }
;ifStatement:            TIF expression TTHEN block { printf("Reduce if to if statement\n"); }
| TIF expression block TELSE block { printf("Reduce ifelse to if statement\n"); }
;

doWhileStatement:       TDO block TWHILE expression { printf("reduce dowhile to while statement\n"); }
;

whileStatement:         TWHILE block expression { printf("Reduce while to while statement\n"); }
;

block:                  TLBRACE statements TRBRACE { printf("Reduce statement list to block\n"); }
| TLBRACE TRBRACE { printf("Reduce empty to block\n"); }
;

variableDeclaration:    identifier_type TIDENTIFIER { printf("reduce uninitialized identifier to variable declaration\n"); }
| identifier_type TIDENTIFIER TEQUAL expression { printf("Reduce initialized identifier to variable declaration\n"); }
;

identifier_type:        TINT_TYPE { printf("Reduce int to identifier type\n"); }
| TDOUBLE_TYPE { printf("Reduce double to identifier type\n"); }
| { printf("Reduce empty to identifier type\n"); }
;expression:             TIDENTIFIER TEQUAL expression { printf("Reduce assignment to expression\n"); }
| TIDENTIFIER { printf("reduce identifier to expression\n"); }
| expression comparison expression { printf("Reduce comparison to expression\n"); }
| TLPAREN expression TRPAREN { printf("Reduce nested expression to expression\n"); }
| expression TPLUS term { printf("Reduce addition to expression\n"); }
| expression  TMINUS term { printf("Reduce subtraction to expression\n"); }
| term { printf("Reduce term to expresson\n"); }
| factor { printf("Reduce factor to expression\n"); }
;

term:                   term TMUL factor { printf("Reduce multiplication to term\n"); }
| term TDIV factor { printf("Reduce division to term\n"); }
;

factor:                 TIDENTIFIER { printf("Reduce identifier to factor\n"); }
| TINTEGER { printf("Reduce integer to numeric\n"); }
| TDOUBLE { printf("Reduce double to numeric\n"); }
;

comparison:             TCEQ { printf("Reduce eq to comparison\n"); }
| TCNE { printf("Reduce ne to comparison\n"); }
| TCLT { printf("Reduce lt to comparison\n"); }
| TCLE { printf("Reduce le to comparison\n"); }
| TCGT { printf("reduce gt to comparison\n"); }
| TCGE { printf("Reduce ge to comparison\n"); }
| TPLUS { printf("Reduce plus to comparison\n"); }
| TMINUS { printf("Reduce minus to comparison\n"); }
| TMUL { printf("Reduce mul to comparison\n"); }
| TDIV { printf("Reduce div to comparison\n"); }
;

Я действительно не понимаю, почему я получаю ошибки, связанные с бесполезными нетерминалами и бесполезными правилами.

Выполнение команды:

bison -d -o parser.cpp parser.y

Я получаю следующие ошибки:

$ bison -d -o parser.cpp parser.y
parser.y: attention: 1 nonterminal useless in grammar
parser.y: attention: 5 rules useless in grammar
parser.y:52.31-34: attention: nonterminal useless in grammar: term
parser.y:135.51-118: attention: rule useless in grammar: expression: expression TPLUS term
parser.y:136.51-123: attention: rule useless in grammar: expression: expression TMINUS term
parser.y:137.51-96: attention: rule useless in grammar: expression: term
parser.y:141.41-103: attention: rule useless in grammar: term: term TMUL factor
parser.y:142.51-107: attention: rule useless in grammar: term: term TDIV factor
parser.y: conflicts: 20 shift/reduce, 14 reduce/reduce
parser.y:145.41-96: attention: rule useless in parser due to conflicts: factor: TIDENTIFIER