Re: Make strict mode more strict?

Some additional observations - On Mon, Dec 28, 2015 at 10:03 AM, Elijah Johnson <ejrx7753@gmail.com> wrote: > Thanks, > > On Mon, Dec 28, 2015 at 6:34 AM, François Laupretre <francois@php.net> > wrote: > >> Hi, >> >> Le 26/12/2015 21:35, Elijah Johnson a écrit : >> >>> Can you explain your statement that this would be a huge and complex >>> work? You must mean that there would be multiple places in the php source >>> code where variables are assigned? I'm not yet discussing performance, but >>> only the aspect of adding the feature. >>> >> >> There may other options I don't know but, AFAIK, this implies adding an >> optional type hint at the zval level. This type hint should be verified at >> least before each conversion. Copy-on-write is an other issue, as it is >> currently not compatible with zval type hints. Seeing only variables with >> well-defined names, and focusing on arrays, only scratches the surface. >> Everything happens at the zval level. So, IMO, attaching type hints to >> variables and properties is a huge and complex work. >> >> Regards >> >> François >> > > I think I see what you are saying. Copy on write takes a reference to the > entire z-val in two local variables, so a type-hint at the z-val level > would be shared. > > This returns us to the insight of the original mailer who suggested that > an object or array variable should be typed by its first-assigned object. > This would simply need to be a global mode - stack-mode-legacy, > stack-mode-static-object-types, and stack-mode-super-strict for those who > want basic types also. > > I'm not saying that this is ideal, just that we need to compromise a bit > to accommodate our existing code base and performance issues. > > The proposal for an additional z-val which stores the class name in the > zval.value member and is counted as null could accommodate the case where > the user wants to assign the type before he has an object. > > I think this is the best option. Another theory I had was to store the > types at the context level in some kind of array, but its really too much.. > > The idea just now proposed of 3 global modes will eliminate the issue of > storing at the z-val level. The mode "stack-mode-static-object-types" is > even already compatible with every line of code that I have properly > written in PHP. > The mode "stack-mode-static-object-types" would ideally also prevent assignment of an object with a current string value, or string placeholder value. What I mean by placeholder value - an additional z-val type "t" returning true for IS_NULL, where the class name id is stored in value union. This would be declared by type hint ex. MyObject $object; If the variable is assigned, MyObject $object = ...; then potentially the same. On assignment would look something like this (pseudo-code): bool checkType(zVal, newZVal) { bool throw_error = false; if (MODE_STACK_TYPE_OBJECT) { if (isObjectType(zVal)) { int class_id= GET_PLACEHOLDER_CLASS(zVal);// ie. zVal.value or value of current object if (class_id !== GET_CLASS(newZVal)) { throw_error = true; } } else if (IS_OBJECT(newZVal) && !IS_NULL(zVal){ throw_error = true; // assigning an object to a non-null, non-object } } if (throw_error) { // assign to null, generate TypeError // ie. Warning: assign of type to type, assigned null value return false; // prevent assignment by caller } return true } Some additional checks would likely be necessary to prevent placeholders from being assigned and returned, and if strict mode was implemented, there would need to be a second placeholder type (or some other means of identification such as a constant). Implementing placeholders isn't a necessary step, but it would make for very readable code.