Re: Re: [RFC] [PRE-VOTE] Union types

> Am 02.06.2016 um 19:33 schrieb Rowan Collins <rowan.collins@gmail.com>: > > On 02/06/2016 18:11, Andrea Faulds wrote: >> That aside, the behaviour the RFC now specifies for how weak typing >> interacts with union types is frighteningly complicated. I don't see how >> it could be anything other than that, but the new complexity this >> introduces to PHP is enough for me to vote against this RFC, even >> ignoring my other concerns. > > That is rather a long-winded set of rules, I agree. I wonder if it's possible for the > order the union type is defined to be taken into account? That way you could specify the rule thus: > > * The type is tested against each type in the union in turn. > * If weak typing is active, scalar types will be coerced where this would normally be allowed, > and passed over where a TypeError would be thrown. > * If strict typing is active, scalar types will be treated the same as non-scalar types, and > must match precisely. > > > So: > > function f(int | float $number) { echo gettype($number); } > f('10'); // int > > function g(float | int $number) { echo gettype($number); } > g('10'); // float > > function h(int | Foo | string) { echo gettype($number); } > h('10'); // int > h(new Foo); // object > h('hello'); // string > > function i(string | int) { echo gettype($number); } > i('10'); // string > i(10); // string > > This last example is the only one that might be a bit surprising - the "| int" in the > type def is actually doing nothing - but there's always scope for user error. > > > In strict mode, things would be a bit different, because no coercion is allowed: > > declare(strict_types=1); > > function f(int | float $number) { echo gettype($number); } > f('10'); // [!] TypeError > > function g(float | int $number) { echo gettype($number); } > g('10'); // [!] TypeError > > function h(int | Foo | string) { echo gettype($number); } > h('10'); // string > h(new Foo); // object > h('hello'); // string > > function i(string | int) { echo gettype($number); } > i('10'); // string > i(10); // int > > > It may be that the implementation makes this prohibitively difficult, but it would certainly be > easier to document than the rules currently proposed. > > Regards, > -- > Rowan Collins > [IMSoP] We had that exact idea relatively early, but it exposes other problems… order suddenly matters. You cannot just add "a" type and get the expected results. E.g. function f(true | string $foo) { ... } everything except 0, ±0, "0" and "" would now return true. That's totally WTF. Sure, it's more friendly for people who want to read *rules*. But it is very bad for intuitivity. Also: > function i(string | int) { echo gettype($number); } > i('10'); // string > i(10); // string This. This is especially bad as it has different behaviors in strict and weak mode then. That's a no-go. The current way is the only viable one, as far as we discovered. Bob