parseSwitchProngList

fn parseSwitchProngList(p: *Parse) !Node.SubRange {
    const scratch_top = p.scratch.items.len;
    defer p.scratch.shrinkRetainingCapacity(scratch_top);

    while (true) {
        const item = try parseSwitchProng(p) orelse break;

        try p.scratch.append(p.gpa, item);

        switch (p.tokenTag(p.tok_i)) {
            .comma => p.tok_i += 1,
            // All possible delimiters.
            .colon, .r_paren, .r_brace, .r_bracket => break,
            // Likely just a missing comma; give error but continue parsing.
            else => try p.warn(.expected_comma_after_switch_prong),
        }
    }
    return p.listToSpan(p.scratch.items[scratch_top..]);
}