`let...else` statements are unstable in solana-frozen-abi-macro-1.16.0

[D0bhareach]

Problem

While compiling anchor-lang = "0.28.0" project have got this error:
.cargo/registry/src/github.com-1ecc6299db9ec823/solana-frozen-abi-macro-1.16.0/src/lib.rs:422:5

422 let Some(expected_digest) = expected_digest else {
423 return Error::new_spanned(
424 TokenStream2::from(item),
425 "the required "digest" = ... attribute is missing.",
...
428 .into()
429 };

= note: see issue #87335 <https://github.com/rust-lang/rust/issues/87335> for more information
= help: add `#![feature(let_else)]` to the crate attributes to enable

For more information about this error, try rustc --explain E0658.
error: could not compile solana-frozen-abi-macro due to previous error
My rustc -V: rustc 1.70.0 (90c541806 2023-05-31)

[Twist96]

I'm having this error too

[PratikBodawala]

I had the same issue, for now, I have downgraded the Rust version to 1.69.0,
additionally, change Solana version to 1.16.1

[sausage-dog]

I get this error with either Solana 1.16.1 or 1.16.0 at rustc 1.69.0.

[smart-tech-master]

me too

[mvines]

@dmakarov - not sure if you have any idea as to what's going on here? The bug reports so far are super low quality here but seems like there's something not right. Unclear if this is an anchor issue or something with the platform tooling

[D0bhareach]

This is issue with Rust version used by libraries I believe it is 1.61 for Solana, honestly don't remember where remember it was in dependencies for workspace. So, I guess, newer syntax is used to compile with older version. So if code above is changed to to if let Some(val) {bla-bla} else {bla-bla } error should disappear.
In order to compile I downgrade versions of dependencies like this:
mpl-token-metadata = {version = "1.12.0", features = ["no-entrypoint"]} solana-program = "=1.14.17"

[dmakarov]

@dmakarov - not sure if you have any idea as to what's going on here? The bug reports so far are super low quality here but seems like there's something not right. Unclear if this is an anchor issue or something with the platform tooling

We'll update platform-tools to latest rust version soon. Until then we could patch frozen-abi-macro/src/lib.rs and add #![feature(let_else)] to enable

solana/frozen-abi/macro/src/lib.rs

Line 422 in 42aa5d2

let Some(expected_digest) = expected_digest else {

I haven't check that it would work with the platform-tools rust compiler, though.

[sausage-dog]

Works for me with this:

[dependencies]
         anchor-lang = "0.26.0"
         anchor-spl = "0.26.0"
         metaplex-token-metadata = { version = "0.0.1", features = ["no-entrypoint"] }
         solana-program = "=1.14.13"
         getrandom = { version = "0.2.9", features = ["custom"] }
         switchboard-v2 = "0.1.15"
         mpl-bubblegum = { version = "0.8.0", features = [ "no-entrypoint" ]}
         spl-account-compression = { version = "0.1.10", features = [ "no-entrypoint" ]}  

at rustc 1.69.0 (84c898d65 2023-04-16)

[marshallr12]

This isn't an anchor specific issue. I can reproduce it attempting to build using rust 1.70 and dependency solana-program 1.16.1:

cargo new test-solana --lib
cd test-solana
cargo add solana-program
cargo build-sbf

Compiling solana-frozen-abi-macro v1.16.1
error[E0658]: let...else statements are unstable
--> /home/marshall/.cargo/registry/src/github.com-1ecc6299db9ec823/solana-frozen-abi-macro-1.16.1/src/lib.rs:422:5
|
422 | / let Some(expected_digest) = expected_digest else {
423 | | return Error::new_spanned(
424 | | TokenStream2::from(item),
425 | | "the required "digest" = ... attribute is missing.",
... |
428 | | .into()
429 | | };
| |______^
|
= note: see issue #87335 rust-lang/rust#87335 for more information
= help: add #![feature(let_else)] to the crate attributes to enable

[mvines]

cargo new test-solana --lib
cd test-solana
cargo add solana-program
cargo build-sbf

These STR worked fine for me.

$ cargo build-sbf --version
solana-cargo-build-sbf 1.16.1
platform-tools v1.37

[dmakarov]

platform-tools 1.37 is based on rust 1.68. let_else feature is stable since rust 1.65, so, indeed, platform-tools v1.37 should work.

[mvines]

I can also confirm the issue reproduces with:

$ cargo build-sbf --version
solana-cargo-build-sbf 1.14.17
sbf-tools v1.29

But this is also expected. One cannot expect to build solana-program 1.16.1 with the platform tools in 1.14

[mvines]

We could try adding https://doc.rust-lang.org/cargo/reference/manifest.html#the-rust-version-field to crates like solana-program to make this error more explicit