Question

I am trying to develop a c# code generator using ANTLR and the StringTemplate library. AntlrWorks can generate the c# parser and lexer files without reporting any errors. However, the c# parser code is not valid and cannot be compiled in visual studio.

Can anyone see what is wrong with the following grammar?

grammar StrucadShape;

options {
    language=CSharp3 ;
   output=template;  

}

@header {using System;}
@lexer::header {using System;} 
@lexer::members {const int HIDDEN = Hidden;}

/*------------------------------------------------------------------
 * PARSER RULES
 *------------------------------------------------------------------*/  

 public shapedef: parameters_def  
                  -> class_temp( parameters={$parameters_def.st} )
                  ;

 parameters_def : (PARAMETERS LPAREN (p+=param) (COMMA (p+=param))* RPAREN )
                  -> parameter_list(params={$p})
                  ;

param   : IDENTIFIER ->Parameter_decl(p={$IDENTIFIER.text});  

/*------------------------------------------------------------------
 * LEXER RULES
 *------------------------------------------------------------------*/    

fragment EOL:'\r'|'\n'|'\r\n'  ;  


 WS : (' ' 
| '\t' 
| EOL) 
{ $channel = HIDDEN; } ;    

 PARAMETERS: 'PARAMETERS';
   COMMA : ',' ;
   LPAREN : '(' ; 
   RPAREN : ')' ;  

fragment LETTER :('A'..'Z' | 'a'..'z');
IDENTIFIER: LETTER (LETTER|DIGIT)*;
INTEGER : (DIGIT)+ ;
FLOAT   : (DIGIT)+'.'(DIGIT)+;
fragment DIGIT  : '0'..'9' ;

This results in the following lines of code in generated parameters_def() method

List<object> list_p = null;

...snipped some code

if (list_p==null) list_p=new List<StringTemplate>(); 

This is failing on the assignment of the List <StringTemplate> to type List<Object>.
The grammar works before I add the string template rules. The error is introduced when I add the (p+=param) syntax required for list processing in the StringTemplate library.

I’ll add my StringTemplate file for completeness, but I don’t think this could be causing an error as it is not loaded until runtime.

group StrucadShape;

Parameter_decl(p)::= "public double <p> { get; set; }"

parameter_list(params) ::=
<<
start expressions
<params; separator="\n">
end
>>

class_temp(  parameters)::=
<<
public class name
{
    <parameters; separator="\n>  
}
>>

A sample input string PARAMETERS( D,B,T)

Antlr Versions

• Antlr3.Runtime 3.4.1.9004
• AntlrWorks 1.4.3

Answer 1

I found a related issue on the Antlr mailing list here.

The solution was to add an ASTLabeltype to the grammar options

options {
    language=CSharp3;   
    output=template;  
    ASTLabelType = StringTemplate;
}