Changing token.type is invalid

[mageniao2]

I added action for LETTERS in the lexer file, which adjusts the token type to VALUE_FUNCTION_NAME (1), but it doesn't take effect, and the output in antlr4-debug is still LETTERS, not VALUE_FUNCTION_NAME.

Tokens:
[@0,0:3='show',<3>,1:0]
[@1,4:4='1',<4>,1:4]
[@2,5:4='<EOF>',<-1>,1:5]

But the syntax tree I get through antlr4-listener outputs the token as VALUE_FUNCTION_NAME
Maybe I got something wrong? My code is as follows:

• launch.json

{
    "version": "2.0.0",
    "configurations": [
        {
            "name": "Debug ANTLR4 grammar",
            "type": "antlr-debug",
            "request": "launch",
            "input": "example.txt",
            "grammar": "lang/exampleParser.g4",
            "actionFile": "lang/example1.js",
            "startRule": "start",
            "printParseTree": true,
            "visualParseTree": true
        }
    ]
}

• lexer and parser

lexer grammar exampleLexer;
tokens {
   VALUE_FUNCTION_NAME, DECORATE_FUNCTION_NAME
}
LETTERS : [a-zA-Z]+ { resetBuiltInToken(this) };
DIGITS : [0-9];
WS : [ \t]+ -> channel(HIDDEN);

parser grammar exampleParser;
options {
    tokenVocab=exampleLexer;
}
start : letters digits?;
letters : (LETTERS | VALUE_FUNCTION_NAME| DECORATE_FUNCTION_NAME);
digits : DIGITS+;

• exampleLexer.tokens

VALUE_FUNCTION_NAME=1
DECORATE_FUNCTION_NAME=2
LETTERS=3
DIGITS=4
WS=5

• lang/example1.js

function resetBuiltInToken(token) {
        console.log(token + "asdasdasdasds")
        token.type = 1;
    }

[mike-lischke]

Is the resetBuiltInToken function actually called? And the this binding is wrong. That's not the token, but the lexer. If all you want is to change the token type use the type lexer command:

LETTERS : [a-zA-Z]+ -> type(VALUE_FUNCTION_NAME);