Nightly Rust
Why Nighly?
The Rust framework currently requires nightly Rust to run. This often causes issues with the inherent instability and frequent changes in the Rust compiler.
While it would be ideal to have our infrastructure running on stable Rust, there are a number of features that we currently require.
This page is intended to provide a list of all these features that we use, and explain what it would take to renounce them and move to stable.
Nightly features
Feature | Why we need it | What it would take to discard |
---|---|---|
never_type and exhaustive_patterns | The codec is optimized to work within smart contracts, but also to be used outside them, in a standard environment. Encoding and decoding functions return Our solution relies heavily on the never type ( Exhaustive patterns are a nice way to engage with code that is guaranteed at compile time to never return an error. | The Exhaustive patterns, if not stabilized soon, could be replaced with regular patterns with an unreacheable clause on the else. |
auto_traits and negative_impls | We have a feature that allows safe conversions from one type to another via the codec. For instance, a smaller integer can be safely cast to a larger one. This feature is central to proxies and transaction syntax. We are using auto-traits and negative implementations to overcome overlaps in the implementations of the | Could be replaced by relying more heavily on proc-macros. We would need a way to generate the Alternately, we could wait for an overlapping marker trait impls. |
try_trait_v2 | Used in the deprecated | Remove |
maybe_uninit_uninit_array and maybe_uninit_array_assume_init | Used in | There are less elegant ways to write that method, without using these features. |
generic_const_exprs | Used everywhere in working with the | Using universal fixed-sized arrays on heap for handling payloads. Might hurt performance, and might also occasionally run into overflows. |
slice_partition_dedup | Used in | We could probably replace that one with an in-house de-duplication function. |
is_sorted | Used in | We could probably replace them with in-house equivalent functions. |
panic_info_message | Used in the wasm adapter to retrieve panic messages, for debugging purposes. | Figuring out a way to use the format function provided by the stable version of the library, without performing memory allocation. |
Deal breakers
Some of the nightly features that we use could be easily replaced with something from stable. However, there are a few essential ones that we have yet no solution for:
generic_const_exprs
This one is very difficult to get rid of without compromising the ManagedVec
functionality. We have also recently added a new ManagedDecimal
component that makes use of this feature. This is the main deal breaker right now for switching to stable Rust.
never_type
Our entire codec relies on the never type. There might be a workaround using void enums, not sure if it works. Fortunately, this feature is close to being stabilized.
auto_traits
and negative_impls
This is not impossible to overcome, but would need a redesign of some of the codec traits.