# Objective
Reduce from scratch build time.
## Solution
Reduce the size of the critical path by removing dependencies between crates where not necessary. For `cargo check --no-default-features` this reduced build time from ~51s to ~45s. For some commits I am not completely sure if the tradeoff between build time reduction and convenience caused by the commit is acceptable. If not, I can drop them.
# Objective
Emitting compile errors produces cleaner messages than panicking in a proc-macro.
## Solution
- Replace match-with-panic code with call to new `bevy_macro_utils::get_named_struct_fields` function
- Replace one use of match-with-panic for enums with inline match
_Aside:_ I'm also the maintainer of [`darling`](https://docs.rs/darling), a crate which provides a serde-like API for parsing macro inputs. I avoided using it here because it seemed like overkill, but if there are plans to add lots more attributes/macros then that might be a good way of offloading macro error handling.
Objective
During work on #3009 I've found that not all jobs use actions-rs, and therefore, an previous version of Rust is used for them. So while compilation and other stuff can pass, checking markup and Android build may fail with compilation errors.
Solution
This PR adds `action-rs` for any job running cargo, and updates the edition to 2021.
There are cases where we want an enum variant name. Right now the only way to do that with rust's std is to derive Debug, but this will also print out the variant's fields. This creates the unfortunate situation where we need to manually write out each variant's string name (ex: in #1963), which is both boilerplate-ey and error-prone. Crates such as `strum` exist for this reason, but it includes a lot of code and complexity that we don't need.
This adds a dead-simple `EnumVariantMeta` derive that exposes `enum_variant_index` and `enum_variant_name` functions. This allows us to make cases like #1963 much cleaner (see the second commit). We might also be able to reuse this logic for `bevy_reflect` enum derives.
