Re: [PATCH] Round the Java rough edges

[Paolo Bonzini]

> If a method is actually invoked anywhere but the user forgets to declare 
> it in Lexer, it will be a compile error anyway, right?  This is similar to 
> when the user forgets yylex or yyerror in Yacc parsers.

With the nice IDEs Java programmers use, however, I prefer to give a
nice error message in the user's lexer code, rather than in the Bison
generated code.

> I believe that would keep things simple and consistent.  
> Moreover, the parser class could use lexer_type_name as the type of its 
> Lexer member (to avoid downcasts) and of the Lexer argument in the parser 
> class constructor.  If the user wanted to make his Lexer subtype an 
> interface or abstract class or final or whatever, that would be totally up 
> to him because he would define the type entirely.
> Now, if you wanted to guarantee that the user defined his lexer type to 
> extend/implement the Lexer interface, Bison could add something like this 
> to the parser class constructor:
> 
>   Lexer lexer_interface = lexer_arg;
> 
> Type compatibility here is checked statically at least by gcj.  Maybe 
> there's a better way to check this.

Yes, that would be good.

> It's supposed to avoid dynamic lookup and thus improve performance, which 
> is usually important for parsers.

Final methods can also avoid dynamic lookup cost and can be inlined.

Paolo