BorshDeserialize gives try_from_slice error - rust

Question

I was exploring the "BorshDeserialize" option in Rust. and noticed the following issues when using trait bounds. Any help is appreciated
Sample code
use borsh::{BorshDeserialize, BorshSerialize};
use solana_program::pubkey::Pubkey;
use std::mem;
#[derive(BorshSerialize, BorshDeserialize, PartialEq, Debug)]
struct SampleData<'a> {
accounts: (&'a Pubkey, &'a Pubkey),
data: String,
timestamp: u64,
owner: &'a Pubkey,
}
fn main() {
println!(
"Size of SampleData is {} bytes",
mem::size_of::<SampleData>()
);
let _pub_key = Pubkey::default();
let _a = SampleData {
accounts: (&_pub_key, &_pub_key),
data: "ABCDE".to_string(),
timestamp: 1643116047,
owner: &_pub_key,
};
let _encoded_a = _a.try_to_vec().unwrap();
println!("{:?}", _encoded_a);
let _decoded_a = SampleData::try_from_slice(&_encoded_a).unwrap();
println!("decoded_a: {:?}", _decoded_a);
}
Error message
error[E0599]: the function or associated item try_from_slice exists
for struct SampleData<'_>, but its trait bounds were not satisfied
--> src/main.rs:27:34 | 6 | struct SampleData<'a> { | --------------------- | | | function or associated item try_from_slice not found for this | doesn't satisfy
SampleData<'_>: BorshDeserialize ... 27 | let _decoded_a =
SampleData::try_from_slice(&_encoded_a).unwrap(); |
^^^^^^^^^^^^^^ function or associated item cannot be called on
SampleData<'_> due to unsatisfied trait bounds | note: the
following trait bounds were not satisfied because of the requirements
of the implementation of BorshDeserialize for _:
(&Pubkey, &Pubkey): BorshDeserialize
&Pubkey: BorshDeserialize --> src/main.rs:5:26 | 5 | #[derive(BorshSerialize, BorshDeserialize, PartialEq, Debug)] | ^^^^^^^^^^^^^^^^ 6 | struct SampleData<'a> { |
^^^^^^^^^^^^^^ = help: items from traits can only be used if the
trait is implemented and in scope = note: the following trait
defines an item try_from_slice, perhaps you need to implement it:
candidate #1: BorshDeserialize = note: this error originates in the derive macro BorshDeserialize (in Nightly builds,
run with -Z macro-backtrace for more info)
For more information about this error, try rustc --explain E0599.
error: could not compile seralize due to previous error

Answer 1

The problem is that SampleData contains references, which isn't supported in normal Borsh deserialization. Borsh creates a new instance of your type based on a slice, but it won't be able to create references.
If you want to stick with Borsh, you should change the type to:
#[derive(BorshSerialize, BorshDeserialize, PartialEq, Debug)]
struct SampleData {
accounts: (Pubkey, Pubkey),
data: String,
timestamp: u64,
owner: Pubkey,
}