> A lot of the ways in which the zig compiler works doesn't use pointers, it uses indices. This stuff is easier to write as safe code, not less easy.

I respectfully disagree. This is only true if you view malloc as qualitatively different from a piece of code that gives you an index for a free object in an object pool.

Provided you don't ask/give back memory from/to the OS, what malloc is doing is giving you an index (pointer) into a pool of bytes, while manipulating an internal bookkeeping structure.

Use after free is just you using an index after said bookeeping structure has marked that piece of memory as available for something else (and perhaps claimed already).

If you have an array of Node structs to represent a graph (like the AST in Zig), and use indices to represent references, you have essentially zero protection in Rust that helps you with finding Node-s that have been used for something else etc.

The 'asking memory from the OS' aspect for malloc doesn't really change the safety of your language compared to this where it matters - if you do use-after-free on a page claimed by the OS, you get a segfault, which immediately tells you there's a problem, which is much better than silent corruption.

At least with malloc, you get debug allocators, or other features that can help you in this case. If you are careless with indices in an object pool, and overwrite stuff, essentially, it's up to you to figure out what went wrong and you have no tools to help you.