Allow combining arg unpacking and named args

Hi internals, Currently, argument unpacking (...$foo) cannot be combined with named arguments (foo: $bar) at all. Both func(...$args, x: $y) and func(x: $y, ...$args) are rejected by the compiler. https://github.com/php/php-src/pull/7009 relaxes this by allowing func(...$args, x: $y). The named arguments are required to come last, because this automatically enforces the invariant that named arguments must be sorted after positional argument. Are there any concerns with relaxing this restriction? Regards, Nikita