Support underscores in identifier without escaping

I’ve come across the following issue when using Writer:

import kastree.ast.Writer
import kastree.ast.psi.Parser


fun main(args: Array<String>) {
    val source = """
        const val c = FOO_BAR
    """

    val file = Parser.parseFile(source)
    println(Writer.write(file))
}

This program will output the following:

const val c = `FOO_BAR`

For c I’d expect (without the back-ticks):

const val c = FOO_BAR

[TAGC]

Nice one man, thanks.

[cretz]

Released