[antlr-interest] Rewrite bug?

[Surj Basan]

Hi Bart,

Thanks for your reply.

I've posted a cut-down grammar which exhibits the errors, along with
generated files here:

http://surge.it/static/antlr/

The grammar rule is in JavaBroken.g:180-183, the Java error is
in JavaBrokenParser.java:8659.

Any help greatly appreciated,
Surj


On 19 July 2012 17:01, Bart Kiers <bkiers at gmail.com> wrote:

> Hi Surj,
>
> Can you:
>
>    - post a complete grammar that reproduces this (not just a small
>    snippet), and
>    - indicate what ANTLR version you're using
>
> Regards,
>
> Bart.
>
>
> On Thu, Jul 19, 2012 at 5:56 PM, Surj Basan <s.basan at surge.it> wrote:
>
>> Hi,
>>
>> No replies yet, so I'm guessing I've either missed something or this is a
>> genuine bug.
>>
>> If anyone knows, could you send a quick reply so I can move forward.
>>
>> To recap: ANTLR is producing code that does not have a variable
>> declaration
>> in the Parser.
>>
>> Thanks,
>> Surj
>>
>> On 16 July 2012 07:24, Surj Basan <s.basan at surge.it> wrote:
>>
>> > Hi All,
>> >
>> > I have a Java grammar (taken from the openjdk, one linked off
>> > the ANTLR site:
>> > http://openjdk.java.net/projects/compiler-grammar/antlrworks/Java.g).
>> >
>> > One of the rewrite rules produces Java code which does not have a var
>> > decl, and so does not compile.
>> >
>> > I took the rule straight out of Terrence Parr's page on rewrite rules
>> and
>> > added it to the grammar (
>> > http://www.antlr.org/wiki/display/ANTLR3/Tree+construction, paragraph
>> > beginning "Using a rewrite rule at a
>> non-extreme-right-edge-of-production
>> > location is ok..").
>> >
>> > Can someone explain if this is a bug in ANTLR? Code is below, for ref.
>> >
>> > Grammar rule:
>> >
>> > statement
>> >     :   [more rules here]
>> >     |   'if' parExpression s1=statement ('else' s2=statement -> ^('if'
>> > parExpression $s1 $s2)
>> >                                         |                      -> ^('if'
>> > parExpression $s1)
>> >                                         )
>> >     [more rules here]
>> >     ;
>> >
>> >
>> > Generated parser code:
>> >
>> >     // $ANTLR start synpred139_AntlrJava
>> >     public final void synpred139_AntlrJava_fragment() throws
>> > RecognitionException {
>> >         void  =null;
>> >
>> >
>> >         // AntlrJava.g:926:42: ( 'else' s2= statement )
>> >         // AntlrJava.g:926:42: 'else' s2= statement
>> >         {
>> >
>> >
>> match(input,KEYWORD_ELSE,FOLLOW_KEYWORD_ELSE_in_synpred139_AntlrJava4927);
>> > if (state.failed) return ;
>> >
>> >         pushFollow(FOLLOW_statement_in_synpred139_AntlrJava4931);
>> >         s2=statement();
>> >
>> >         state._fsp--;
>> >         if (state.failed) return ;
>> >
>> >         }
>> >
>> >     }
>> >
>> > (For what it's worth, I find that various permutations of rewrite rules
>> > exhibit the same behaviour: missing var decls in the generated parser.
>> > Java.g is a pretty complex grammar. Would I have more luck if I split
>> the
>> > grammar into the lexer/parser and a separate tree building one, instead
>> of
>> > combining it all into a single file?)
>> >
>> > Any help greatly appreciated.
>> >
>> > Thanks,
>> > Surj
>> >
>>
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>