It would be nice to have a more indepth discussion of the issues that have been found with compile-time programming, rather than uncritical acclaim. Staged programming is not new, and people have run into many issues and design tradeoffs in that time. (E.g. the same stuff has been done in Lisps for decades, though most Lisps don't have a type system, which makes things a bit more complicated.)
Some of the issues that come to mind:
* Implementing generics in this way breaks parametricity. Simply put, parametricity means being able to reason about functions just from their type signature. You can't do this when the function can do arbitrary computation based on the concrete type a generic type is instantiated with.
* It's not clear to me how Zig handles recursive generic types. Generally, type systems are lazy to allow recursion. So I can write something like
type Example = Something[Example]
(Yes, this is useful.)
* Type checking and compile-time computation can interact in interesting ways. Does type checking take place before compile-time code runs, after it runs, or can they be interleaved? Different choices give different trade-offs. It's not clear to me what Zig does and hence what tradeoffs it makes.
* The article suggests that compile-time code can generate code (not just values) but doesn't discuss hygiene.
There is a good discussion of some issues here: https://typesanitizer.com/blog/zig-generics.html
Some of the issues that come to mind:
* Implementing generics in this way breaks parametricity. Simply put, parametricity means being able to reason about functions just from their type signature. You can't do this when the function can do arbitrary computation based on the concrete type a generic type is instantiated with.
* It's not clear to me how Zig handles recursive generic types. Generally, type systems are lazy to allow recursion. So I can write something like
type Example = Something[Example]
(Yes, this is useful.)
* Type checking and compile-time computation can interact in interesting ways. Does type checking take place before compile-time code runs, after it runs, or can they be interleaved? Different choices give different trade-offs. It's not clear to me what Zig does and hence what tradeoffs it makes.
* The article suggests that compile-time code can generate code (not just values) but doesn't discuss hygiene.
There is a good discussion of some issues here: https://typesanitizer.com/blog/zig-generics.html