this.tokenSource.nextToken is not a function

[lan...@clarkson.edu]

Hello,

I am using Antlr 4.7 to generate a JavaScript lexer/parser. I am getting the this.tokenSource.nextToken is not a function error for even the simplest grammar, taken from the Antlr homepage:

Grammar

grammar JASS;
prog:    (expr NEWLINE)* ;
expr:    expr ('*'|'/') expr
    |    expr ('+'|'-') expr
    |    INT
    |    '(' expr ')'
    ;
NEWLINE : [\r\n]+ ;
INT     : [0-9]+ ;

Code

var input = '100+2*34';
var chars = new antlr4.InputStream(input);
var lexer = JASSLexer.JASSLexer(chars);
var tokens  = new antlr4.CommonTokenStream(lexer);
var parser = new JASSParser.JASSParser(tokens);
parser.buildParseTrees = true;
var tree = parser.prog();

Error trace

TypeError: this.tokenSource.nextToken is not a function
    at CommonTokenStream.BufferedTokenStream.fetch (C:\Users\Greg\Desktop\JASS\node_modules\antlr4\BufferedTokenStream.js:140:28)
    at CommonTokenStream.BufferedTokenStream.sync (C:\Users\Greg\Desktop\JASS\node_modules\antlr4\BufferedTokenStream.js:125:22)
    at CommonTokenStream.BufferedTokenStream.setup (C:\Users\Greg\Desktop\JASS\node_modules\antlr4\BufferedTokenStream.js:228:7)
    at CommonTokenStream.BufferedTokenStream.lazyInit (C:\Users\Greg\Desktop\JASS\node_modules\antlr4\BufferedTokenStream.js:223:8)
    at CommonTokenStream.LT (C:\Users\Greg\Desktop\JASS\node_modules\antlr4\CommonTokenStream.js:68:10)
    at JASSParser.Parser.enterRule (C:\Users\Greg\Desktop\JASS\node_modules\antlr4\Parser.js:416:32)
    at JASSParser.prog (C:\Users\Greg\Desktop\JASS\syntax\JASSParser.js:147:10)
    at Object.<anonymous> (C:\Users\Greg\Desktop\JASS\index.js:16:19)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)

Any ideas? I've tried following each error up the call stack, but am not familiar enough with the code to know the issue here. Thanks in advance.

[Eric Vergnaud]

You're missing the 'new' in var lexer = JASSLexer.JASSLexer(chars);