2 ms·

Well its a bit of an issue with escape analysis to know for sure that something is or isn't called before the handler returns. Imagine a scenario where multipl

by jayd16 4y ago

Well its a bit of an issue with escape analysis to know for sure that something is or isn't called before the handler returns. Imagine a scenario where multiple threads get involved. That would be a lot to track. I don't think its a great pattern but just speaking hypothetically, if you ensure that only valid Response instances exist (because you organized the constructors to only make valid instances and nulls are invalid) you can force the user to return a valid instance.

Someone 4y ago
Yes, but there’s related prior art. Firstly, Java requires the compiler can prove variables are initialized before first use, and there’s a precisely described, fairly restricted algorithm that must be able to do that. Similarly, Rust can’t correctly accept all code without ownership issues, so it supports only a subset of such code (in this case, AFAIK, that set is defined by the compiler, and growing over time) In both cases the language designers on purpose limited what programs are valid so that the compiler can enforce certain constraints, eradicating a class of bugs. I wonder whether there’s a language that works similar for this kind of constraints. C++ destructors can do it for simple things such as “you must close this file before returning”, but that’s because the compiler will insert the call where needed. Enforcing “you must call f before you ever call g” also is doable in simple cases: have f return a value of a type that must be passed to g or an object foo on which one g is implemented as a member: foo.g(). I’m not aware of any language that allows for more complex state transitions, though. Edit: I think Rust can do (¿most of?) this by having a function take ownership of an object passed in, thus preventing further calls to it, and returning a new object on which only the then permissible calls can be made. I’m not sure one can require that to end with a ‘stopping state’ object, though.
mjevans 4y ago
... Warning ${function} took too long to check and was skipped; consider refactoring if possible or add UNSAFE.NoEscapeTracking to the function signature. Maybe something like that to let the humans know and make higher level choices?

by jayd16 4y ago

Someone 4y ago

Yes, but there’s related prior art. Firstly, Java requires the compiler can prove variables are initialized before first use, and there’s a precisely described, fairly restricted algorithm that must be able to do that. Similarly, Rust can’t correctly accept all code without ownership issues, so it supports only a subset of such code (in this case, AFAIK, that set is defined by the compiler, and growing over time) In both cases the language designers on purpose limited what programs are valid so that the compiler can enforce certain constraints, eradicating a class of bugs. I wonder whether there’s a language that works similar for this kind of constraints. C++ destructors can do it for simple things such as “you must close this file before returning”, but that’s because the compiler will insert the call where needed. Enforcing “you must call f before you ever call g” also is doable in simple cases: have f return a value of a type that must be passed to g or an object foo on which one g is implemented as a member: foo.g(). I’m not aware of any language that allows for more complex state transitions, though. Edit: I think Rust can do (¿most of?) this by having a function take ownership of an object passed in, thus preventing further calls to it, and returning a new object on which only the then permissible calls can be made. I’m not sure one can require that to end with a ‘stopping state’ object, though.

mjevans 4y ago

... Warning ${function} took too long to check and was skipped; consider refactoring if possible or add UNSAFE.NoEscapeTracking to the function signature. Maybe something like that to let the humans know and make higher level choices?