CODEWITHSUNDEEP
antlr
Felix Bembrick
Felix Bembrick

Reputation: 233

ANTLR error(99) grammar has no rules

I previously posted about my first attempt at using ANTLR when I was having issues with left recursion.

Now that I have resolved those issues, I am getting the following error when I try to use org.antlr.v4.Tool to generate the code:

error(99): C:test.g4::: grammar 'test' has no rules

What are the possible reasons for this error? Using ANTLRWorks I can certainly see rules in the Parse Tree so why can't it see them? Is it because it cannot find a suitable START rule?

Upvotes: 11

Views: 7744

Answers (7)

vdua
vdua

Reputation: 1331

I think Antlr expects the first rule name to be in small case. I was getting the same error with my grammar

grammar ee;
Condition : LogicalExpression ;
LogicalExpression : BooleanLiteral ; 
BooleanLiteral :  True ;
True : 'true' ;

By changing the first production rule in the grammar to lower case it solved the issue i.e. the below grammar worked for me.

grammar ee;
condition : LogicalExpression ;
LogicalExpression : BooleanLiteral ; 
BooleanLiteral :  True ;
True : 'true' ;

Note: It is my personal interpretation, I couldn't find this reasoning in the online documentation.

Edit: The production rules should begin with lower case letters as specified in the latest docs [1]

[1] https://github.com/antlr/antlr4/blob/master/doc/lexicon.md#identifiers

Upvotes: 11

aicha ouadah
aicha ouadah

Reputation: 21

I had the same problem, and this means that your grammar has no Syntactic rules. So in order to avoid this error, you need to write at least one Syntactic rule.

Upvotes: 0

Chet
Chet

Reputation: 1

Changing the first rule to start with a lower case character worked for me.

Upvotes: 0

Cjo
Cjo

Reputation: 1351

I also got the same error but could not fix it. I downloaded antlrworks-1.4.jar and it's working perfectly.

Download >> antlrworks-1.4.jar

Upvotes: 0

Markoorn
Markoorn

Reputation: 2565

I'm not sure if you've found the solution for this, but I had the same problem and fixed it by changing my start symbol to 'prog'. So for example, the first two lines of your .g4 file would be: 

    grammar test;
    prog : <...> ;

Where <...> will be your first derivation.

Upvotes: 2

Dio
Dio

Reputation: 348

I just got that error as well (antlworks 2.1). switching from RULE : THIS | THAT ; to rule : this | that ; for parser rules (i.e. from uppercase to lowercase) solved the problem!

EDIT The above correction holds only for RULE , what follows after the : can be any combination of lexer/parser rules

Upvotes: 1

Roy
Roy

Reputation: 71

The most likely cause is just what the error message suggests. And the most likely reason for that is that you have not saved your grammar to the file--or if you're using ANTLRWorks2--ANTLRWorks hasn't saved your work to the file. I have no idea why ANTLRWorks doesn't save reliably.

Upvotes: 0

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