In the 2024 edition of Rust, `serde`s macros for `serialize_with` can
lead to a temporary lifetime error such as:
```
error[E0716]: temporary value dropped while borrowed
--> my-binary/src/main.rs:6:10
|
6 | #[derive(MyDerive)]
| ^^^^^^^-
| | |
| | temporary value is freed at the end of this statement
| creates a temporary value which is freed while still in use
| borrow later used by call
| in this derive macro expansion
|
::: /private/tmp/life/my-project/my-macro/src/lib.rs:6:1
|
6 | pub fn my_derive(_input: TokenStream) -> TokenStream {
| ---------------------------------------------------- in this expansion of `#[derive(MyDerive)]`
|
= note: consider using a `let` binding to create a longer lived value
```
This is because the macro code takes a reference to struct inside of a
block, which then goes out of scope when `serde` passes it to a
function.
To resolve this, we move the reference to outside of the block, to
ensure that the lifetime extends into the function call.
Signed-off-by: Andrew V. Teylu <andrew.teylu@vector.com>
