Rust derive default on enum to remove need for impl block - rust

Question

~/Workspace/microscaler/docker-api-rs on fix/linting-issues cargo clippy --all-targets --all-features -- -D clippy::all -Z macro-backtrace ✔ at 20:14:11
Checking docker-api v0.12.2 (/Users/casibbald/Workspace/microscaler/docker-api-rs)
error: this `impl` can be derived
--> src/opts/container.rs:50:1
|
50 | / impl Default for Isolation {
51 | | fn default() -> Self {
52 | | Isolation::Default
53 | | }
54 | | }
| |_^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#derivable_impls
= note: `-D clippy::derivable-impls` implied by `-D clippy::all`
= help: remove the manual implementation...
help: ...and instead derive it...
|
43 | #[derive(Default)]
|
help: ...and mark the default variant
|
45 ~ #[default]
46 ~ Default,
|
error: could not compile `docker-api` due to previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `docker-api` due to previous error
The following help page is referred to:
https://rust-lang.github.io/rust-clippy/master/index.html#derivable_impls
However, adding #[derive(Default)] does not seem so straightforward when multiple items exist.
Source code here:
https://github.com/microscaler/docker-api-rs/blob/d85deec98a10dcc2f6a1ed7c324010e28d437941/src/opts/container.rs#L50
The following does not work:
Checking docker-api v0.12.2 (/Users/casibbald/Workspace/microscaler/docker-api-rs)
error: no default declared
--> src/opts/container.rs:41:10
|
41 | #[derive(Default, Clone, Debug, Serialize, Deserialize)]
| ^^^^^^^ in this derive macro expansion
|
::: /Users/casibbald/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/default.rs:186:1
|
186 | pub macro Default($item:item) {
| ----------------- in this expansion of `#[derive(Default)]`
|
= help: make a unit variant default by placing `#[default]` above it

Answer 1

Read the compiler/linter messages, they tell you exactly what to do:
= help: remove the manual implementation...
help: ...and instead derive it...
|
43 | #[derive(Default)]
|
help: ...and mark the default variant
|
45 ~ #[default]
46 ~ Default,
|
= help: make a unit variant default by placing `#[default]` above it
Like this:
#[derive(Default, Clone, Debug)]
pub enum Isolation {
#[default]
Default,
Process,
HyperV,
}