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POC#, ANTLR, ECMAScript grammar troubles
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  1. POC#, ANTLR, ECMAScript grammar troubles
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    copied!<p>I'm trying to parse JavaScript (ECMASCript) with C#.</p> <p>I found the following instruction on how to create new project: <a href="http://www.antlr.org/wiki/pages/viewpage.action?pageId=557075" rel="nofollow noreferrer">http://www.antlr.org/wiki/pages/viewpage.action?pageId=557075</a></p> <p>So I've downloaded ANTLRWorks, ANTLR v3, unpacked ANTLR, created a VS2010 project (.NET4), added references, checked and generated the grammar.</p> <p>Then I recieved a lot of compilation error:</p> <blockquote> <p>The type or namespace name 'AstParserRuleReturnScope' could not be found (are you missing a using directive or an assembly reference?)</p> <p>The type or namespace name 'GrammarRule' could not be found (are you missing a using directive or an assembly reference?)</p> </blockquote> <p>Stackoverlowed for them and got a solution: <a href="https://stackoverflow.com/questions/7614953/antlr-c-sharp-errors-when-integrating-into-vs2008">antlr c# errors when integrating into VS2008</a></p> <p>So I've downloaded new runtime, overwrite the old one and recompiled the project and got</p> <blockquote> <p>The name 'HIDDEN' does not exist in the current context d:\Workspace.1\ScriptParser\ScriptParser\TestLexer.cs</p> </blockquote> <p>Ok, I've changed HIDDEN to Hidden as recommended at in the following conversation: <a href="http://www.mail-archive.com/antlr-interest@antlr.org/msg06052.html" rel="nofollow noreferrer">[antlr-interest] How viable is the Csharp3 target? (more specific questions)</a></p> <p>Now I'm trying to parse the input. I found a few examples and wrote the following code:</p> <pre><code>using Antlr.Runtime; namespace ScriptParser { class Program { static void Main(string[] args) { var stream = new ANTLRStringStream("1+2"); var lexer = new TestLexer(stream); var tokenStream = new CommonTokenStream(lexer); var parser = new TestParser(tokenStream); // what exactly should be here??? } } } </code></pre> <p>My goal is to parser JavaScript file with ANTLR but it seems that it will be the not as easy as I thought...</p> <p><strong>Update:</strong></p> <p>As suggested in <a href="https://stackoverflow.com/questions/6411520/why-are-antlr3-c-sharp-parser-methods-private">Why are antlr3 c# parser methods private?</a> I've modified the Test.g grammar by adding the "public" modified before the expr rule:</p> <pre><code>public expr : mexpr (PLUS^ mexpr)* SEMI! ; </code></pre> <p>and then regenerated the code, replaced HIDDEN to Hidden (again) and modified the code as follows:</p> <pre><code>var stream = new ANTLRStringStream("1+2"); var lexer = new TestLexer(stream); var tokenStream = new CommonTokenStream(lexer); var parser = new TestParser(tokenStream); var result = parser.expr(); var tree = (CommonTree)result.Tree; </code></pre> <p>And not it is crashing on the line</p> <pre><code>root_0 = (object)adaptor.Nil(); </code></pre> <p>in the following generated code</p> <pre><code>try { DebugEnterRule(GrammarFileName, "expr"); DebugLocation(7, 0); try { // d:\\Workspace.1\\ScriptParser\\ScriptParser\\Test.g:7:13: ( mexpr ( PLUS ^ mexpr )* SEMI !) DebugEnterAlt(1); // d:\\Workspace.1\\ScriptParser\\ScriptParser\\Test.g:7:15: mexpr ( PLUS ^ mexpr )* SEMI ! { root_0 = (object)adaptor.Nil(); DebugLocation(7, 15); PushFollow(Follow._mexpr_in_expr31); </code></pre> <p>with the NullReferenceException message because the adapter is null.</p> <p>I've resolved it by adding</p> <pre><code>parser.TreeAdaptor = new CommonTreeAdaptor(); </code></pre> <p><strong>Update 2:</strong></p> <p>So, finally I've started with my primary task: parse JavaScript.</p> <p><a href="http://www.antlr.org/grammar/list" rel="nofollow noreferrer">ANTLR highlights</a> the ECMAScript grammar by Chris Lambrou.</p> <p>So I've generated lexer/parser and run it with the very simple JavaScript code:</p> <pre><code>var f = function () { }; </code></pre> <p>and the parsing fails with the following output from tree.ToStringTree():</p> <pre><code>&lt;error: var q = function () { };&gt; </code></pre>
 

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