Error in array declaration grammar - yacc

Question

%token DIGIT RETURN IDENTIFIER COLON COMMA ELSE IF NL KEYWORD BR READ WRITE WHILE EQUAL
%start y2
%left '-'
%left '+'
%right '='
%%
stmt1:KEYWORD IDENTIFIER X1 //for initialization.
;
y2:stmt1 stmt2 //y2 is starting variable
|
;
X1:COLON {printf(" for int a/ char a");}
|'['DIGIT']'COLON {printf("for array declarations");}
;
stmt2:KEYWORD IDENTIFIER"("stmt3")"stmt5 {printf("for functions");}
|
;
stmt3:KEYWORD IDENTIFIER X2
|
;
X2:stmt4 {printf("for parameter int/char");}
|"["DIGIT"]"COLON {printf("for parameter int arr[]/char arr[]");} //in this production parser is not responding
;
stmt4:COMMA stmt3 {printf("to have multiple arguments");}
|
;
%%
I am parsing string int a[10];
but it instead of parsing,
execute yyerror() every time.
This code parses int a; single statement char a; also.

Answer 1

Make sure that your lexer returns '[' when it sees an open bracket.
Mixing single-quoted tokens like '[' and named tokens like COLON is confusing and suggests you are copy-and-pasting from different sources, rather than actually designing a program. Since the lexer and parser must agree on the handling of tokens, this form of creating programs is error-prone. I recommend using single-quoted single-character tokens throughout, since it is more readable and simplifies the lexer.
With respect to X2, there is a difference between '[' and "[". You probably want the first one. The same problem is found in stmt2, which uses​ "(" and ")" instead of the single-quoted versions.