parseSwitchProng

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

    const is_inline = p.eatToken(.keyword_inline) != null;

    if (p.eatToken(.keyword_else) == null) {
        while (true) {
            const item = try p.parseSwitchItem() orelse break;
            try p.scratch.append(p.gpa, item);
            if (p.eatToken(.comma) == null) break;
        }
        if (scratch_top == p.scratch.items.len) {
            if (is_inline) p.tok_i -= 1;
            return null;
        }
    }
    const arrow_token = try p.expectToken(.equal_angle_bracket_right);
    _ = try p.parsePtrIndexPayload();

    const items = p.scratch.items[scratch_top..];
    if (items.len <= 1) {
        return try p.addNode(.{
            .tag = if (is_inline) .switch_case_inline_one else .switch_case_one,
            .main_token = arrow_token,
            .data = .{ .opt_node_and_node = .{
                if (items.len >= 1) items[0].toOptional() else .none,
                try p.expectSingleAssignExpr(),
            } },
        });
    } else {
        return try p.addNode(.{
            .tag = if (is_inline) .switch_case_inline else .switch_case,
            .main_token = arrow_token,
            .data = .{ .extra_and_node = .{
                try p.addExtra(try p.listToSpan(items)),
                try p.expectSingleAssignExpr(),
            } },
        });
    }
}