[antlr-interest] Re: Problems with token class-type override feature (with C# codegen)

lgcraymer lgc at mail1.jpl.nasa.gov
Mon Jul 29 11:24:15 PDT 2002


Manually constructed AST nodes use the default AST type--Ric says that 
he's fixed that for C++ (although I don't remember if that is yet in 
an available version).  The ASTFactory needs to use a table of token 
values and classes to make this work properly.

For automatic construction, ANTLR creates ASTs using the specified 
classes, but doesn't do typecasting properly.  The solution that I 
found was to modify the code generation to specify all AST variables 
declared by ANTLR as being of type "AST"--that effectively avoids the 
typecasting problems since ANTLR only references the child and sibling 


--- In antlr-interest at y..., "micheal_jor" <open.zone at v...> wrote:
> Hi,
> While exploring the idea of custom AST classes, I noticed that the 
> feature is supposed to that allow me to specify alternative AST 
> classes on a per-token basis isn't working.
> I specified the following in my grammar but in the generated code 
> default AST class type is still used for all nodes. There is no 
> reference to the specified class type at all.
>     tokens
>     {
>       LOCK_STMT<AST=LockStatement>;
>     }
> I though it might be related to the fact that I use manual 
> treebuilding commands such as:
>     lockStatement
>       :  LOCK! 
>          (  ( LPAREN! stmtList )=> LPAREN! expression RPAREN! block
>             { ## = #( [LOCK_STMT, "LOCK_STMT"], ##); } 
>          |  block
>             { ## = #( [LOCK_DIRECTIVE, "LOCK_DIRECTIVE"], ##); } 
>          )
>       ;
> This is with C#. Does this feature work at all?. If it does, can 
> anyone give me a quick pointer to what I should look out for in 
> fixing the C# codegen pls (it needs an update soon anyways 
> Micheal


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