[antlr-interest] empty rule catches unthrown RecognitionException

[Terence Parr]

should be a beta3 or seomthing there.
T
On Jul 1, 2011, at 3:34 PM, Trevor John Thompson wrote:

> Presuming that "latest beta" is antlr-3.4rc2-complete.jar, i get:
> 
> java -jar /Users/Local/antlr-3.4rc2-complete.jar Empty.g
> javac -cp /Users/Local/antlr-3.4rc2-complete.jar EmptyParser.java
> EmptyParser.java:167: exception org.antlr.runtime.RecognitionException is never thrown in body of corresponding try statement
>        catch (RecognitionException re) {
>        ^
> 1 error
> 
> On 2011 Jul 1, at 15:12, Terence Parr wrote:
> 
>> i fixed this in latest beta for 3.4...can you try that?
>> Ter
>> On Jul 1, 2011, at 3:10 PM, Trevor John Thompson wrote:
>> 
>>> I have a grammar in which i wish to create an imaginary AST node, and then have an action treat that node. The most straightforward expression i have devised is:
>>> grammar Empty;
>>> options {output=AST;}
>>> tokens {Imaginary;}
>>> @members {void treat(Object t){}}
>>> 
>>> parse: empty EOF! {treat($empty.tree);};
>>> empty: ->^(Imaginary);
>>> 
>>> However, the generated EmptyParser.java fails to compile because empty() catches RecognitionException, which is never thrown.
>>> 
>>> I am working around this by:
>>> empty: ->^(Imaginary)|Imaginary;
>>> which works because the imaginary token can never be produced by the lexer.
>>> 
>>> Is there some other way i should be going about this?
>>> --
>>> Trevor John Thompson    (425) 246-4023
>>> net: tijet at me.com
>>> Quidquid Latine scriptum sit, altum videtur.
>>> 
>>> 
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>> 
> 
> 
> 
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