Matt Godbolt sold me on Rust by showing me C++

The one thing that sold me on Rust (going from C++) was that there is a single way errors are propagated: the Result type. No need to bother with exceptions, functions returning bool, functions returning 0 on success, functions returning 0 on error, functions returning -1 on error, functions returning negative errno on error, functions taking optional pointer to bool to indicate error (optionally), functions taking reference to std::error_code to set an error (and having an overload with the same name that throws an exception on error if you forget to pass the std::error_code)...I understand there's 30 years of history, but it still is annoying, that even the standard library is not consistent (or striving for consistency).

Then you top it on with `?` shortcut and the functional interface of Result and suddenly error handling becomes fun and easy to deal with, rather than just "return false" with a "TODO: figure out error handling".

> The one thing that sold me on Rust (going from C++) was that there is a single way errors are propagated: the Result type. No need to bother with exceptions

This isn't really true since Rust has panics. It would be nice to have out-of-the-box support for a "no panics" subset of Rust, which would also make it easier to properly support linear (no auto-drop) types.

It's pretty difficult to have no panics, because many functions allocate memory and what are they supposed to do when there is no memory left? Also many functions use addition and what is one supposed to do in case of overflow?

>many functions allocate memory and what are they supposed to do when there is no memory left?

Return an AllocationError. Rust unfortunately picked the wrong default here for the sake of convenience, along with the default of assuming a global allocator. It's now trying to add in explicit allocators and allocation failure handling (A:Allocator type param) at the cost of splitting the ecosystem (all third-party code, including parts of libstd itself like std::io::Read::read_to_end, only work with A=GlobalAlloc).

Zig for example does it right by having explicit allocators from the start, plus good support for having the allocator outside the type (ArrayList vs ArrayListUnmanaged) so that multiple values within a composite type can all use the same allocator.

>Also many functions use addition and what is one supposed to do in case of overflow?

Return an error ( https://doc.rust-lang.org/stable/std/primitive.i64.html#meth... ) or a signal that overflow occurred ( https://doc.rust-lang.org/stable/std/primitive.i64.html#meth... ). Or use wrapping addition ( https://doc.rust-lang.org/stable/std/primitive.i64.html#meth... ) if that was intended.

Note that for the checked case, it is possible to have a newtype wrapper that impls std::ops::Add etc, so that you can continue using the compact `+` etc instead of the cumbersome `.checked_add(...)` etc. For the wrapping case libstd already has such a newtype: std::num::Wrapping.

Also, there is a clippy lint for disallowing `+` etc ( https://rust-lang.github.io/rust-clippy/master/index.html#ar... ), though I assume only the most masochistic people enable it. I actually tried to enable it once for some parsing code where I wanted to enforce checked arithmetic, but it pointlessly triggered on my Checked wrapper (as described in the previous paragraph) so I ended up disabling it.

> Rust unfortunately picked the wrong default here

I partially disagree with this. Using Zig style allocators doesn't really fit with Rust ergonomics, as it would require pretty extensive lifetime annotations. With no_std, you absolutely can roll your own allocation styles, at the price of more manual lifetime annotations.

I do hope though that some library comes along that allows for Zig style collections, with the associated lifetimes... (It's been a bit painful rolling my own local allocator for audio processing).

Explicit allocators do work with Rust, as evidenced by them already working for libstd's types, as I said. The mistake was to not have them from day one which has caused most code to assume GlobalAlloc.

As long as the type is generic on the allocator, the lifetimes of the allocator don't appear in the type. So eg if your allocator is using a stack array in main then your allocator happens to be backed by `&'a [MaybeUninit<u8>]`, but things like Vec<T, A> instantiated with A = YourAllocator<'a> don't need to be concerned with 'a themselves.

Eg: https://play.rust-lang.org/?version=nightly&mode=debug&editi... do_something_with doesn't need to have any lifetimes from the allocator.

If by Zig-style allocators you specifically mean type-erased allocators, as a way to not have to parameterize everything on A:Allocator, then yes the equivalent in Rust would be a &'a dyn Allocator that has an infectious 'a lifetime parameter instead. Given the choice between an infectious type parameter and infectious lifetime parameter I'd take the former.