ANTLR4 can only parse a class statement, not the whole file Code Answer

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I created a simple code to parse PHP file:

<?php
namespace aaa;

class Xyz {

}

I wrote a parser using ANTL4 and this grammar: https://github.com/antlr/grammars-v4/tree/master/php:

PhpLexer lexer = new PhpLexer(new ANTLRInputStream((new BufferedReader(new FileReader("./code/test.php")))));
CommonTokenStream tokens = new CommonTokenStream(lexer);
PhpParser parser = new PhpParser(tokens);

PhpParserBaseListener listener = new PhpParserBaseListener();

parser.addParseListener(listener);
parser.classDeclaration().enterRule(listener);

parser.getSerializedATN();

It returns an error:

line 3:0 mismatched input ‘namespace’ expecting {‘abstract’, ‘class’, ‘final’, ‘interface’, ‘partial’, ‘private’, ‘trait’}

But when I remove “namespace aaa;” statement:

<?php

class Xyz {

}

everything is fine.

How to fix that?

Answer

Since you don’t show any of your grammar, it’s not possible to provide a specific answer. Also I really don’t know enough about the PHP runtime for Antlr to more than hazard a guess at what this does:

parser.classDeclaration().enterRule(listener);

But generally, Antlr4 creates an interface for every non-terminal rule, so I presume that parser.classDeclaration() corresponds to the classDeclaration rule, which presumably represents a class declaration, and not the entire program. Probably you should change classDeclaration to whatever the top-level rule in your grammar is.

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