renderExtraNewlineToken

fn renderExtraNewlineToken(r: *Render, token_index: Ast.TokenIndex) Error!void {
    const tree = r.tree;
    const ais = r.ais;
    const token_start = tree.tokenStart(token_index);
    if (token_start == 0) return;
    const prev_token_end = if (token_index == 0)
        0
    else
        tree.tokenStart(token_index - 1) + tokenSliceForRender(tree, token_index - 1).len;

    // If there is a immediately preceding comment or doc_comment,
    // skip it because required extra newline has already been rendered.
    if (mem.indexOf(u8, tree.source[prev_token_end..token_start], "//") != null) return;
    if (tree.isTokenPrecededByTags(token_index, &.{.doc_comment})) return;

    // Iterate backwards to the end of the previous token, stopping if a
    // non-whitespace character is encountered or two newlines have been found.
    var i = token_start - 1;
    var newlines: u2 = 0;
    while (std.ascii.isWhitespace(tree.source[i])) : (i -= 1) {
        if (tree.source[i] == '\n') newlines += 1;
        if (newlines == 2) return ais.insertNewline();
        if (i == prev_token_end) break;
    }
}