[antlr-interest] Passing user defined exceptions through the parser.

[Sam Harwell]

I have implemented this feature in my local copy of the C# port of the
ANTLR tool, but I still need to make a decision about a couple aspects
of it. Due to the declaration of BaseRecognizer.mTokens, non-fragment
rules in a lexer that uses the Java target cannot specify user
exceptions.

This condition only applies to the Java target, and even then a user
could derive from a class other than BaseRecognizer as a workaround.
Based on this, the following conditions need to be considered:

* All parser rules may have user-specified exceptions in the exceptions
specification (nothing to decide on here)
* In theory, all fragment rules in a lexer can have user-specified
exceptions, as long as they are handled by the non-fragment lexer rules
that reference them. Should we allow this?
* In theory, non-fragment lexer rules can specify user exceptions so
long as the generated class derives from a user-created class where the
mTokens function declares other exceptions. Other targets such as C# are
not limited like this, and the exceptions spec would only be used as
part of an XML comment at the function declaration. Should we allow this
in the grammar?

Sam

-----Original Message-----
From: antlr-interest-bounces at antlr.org
[mailto:antlr-interest-bounces at antlr.org] On Behalf Of Peter C. Chapin
Sent: Wednesday, January 14, 2009 6:32 AM
Cc: antlr-interest
Subject: Re: [antlr-interest] Passing user defined exceptions
throughtheparser.

Sam Harwell wrote:

> I just checked and the feature is not implemented in the code
generator
> yet. At least in the C# port of the tool it will cause recognition
> exceptions if you use it in a grammar right now.
>   

Okay, thanks for pointing this out. I'll take a look and keep my eye on
it.

Peter

> -----Original Message-----
> From: antlr-interest-bounces at antlr.org
> [mailto:antlr-interest-bounces at antlr.org] On Behalf Of Sam Harwell
> Sent: Tuesday, January 13, 2009 10:06 AM
> To: Peter C. Chapin
> Cc: antlr-interest
> Subject: Re: [antlr-interest] Passing user defined exceptions through
> theparser.
>
> There is a throwsSpec in the ANTLR tool grammar that *should* be able
to
> be used like this:
>
> my_rule /*returns [Object o]*/ throws RecognitionException,
> OperationCanceledException
>  : ...
>  ;
>
> It doesn't apply to C# so it's not implemented in my CSharp3 target.
>
> Sam
>   


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