Cannot create a PublicImmutable Storage that holds an array

[0xThemis]

Version

I am using aztec-packages-v0.69.1.

Problem

The PublicImmutable Storage struct is expected to hold arbitrary data types provided as template parameters. While this functionality works for ordinary elements, like Field, it fails when attempting to use arrays such as [Field; 3]. The compiler crashes with a panic.

Steps to Reproduce

Setup inspired by the Counter Tutorial:

1. Create a new project:

   mkdir immutable-array
   cd immutable-array
   mkdir contracts
   

2. Create a contract:

cd contracts
aztec-nargo new --contract immutable_array

3. Add dependencies to Nargo.toml:

[dependencies]
aztec = { git="https://github.com/AztecProtocol/aztec-packages/", tag="aztec-packages-v0.69.1", directory="noir-projects/aztec-nr/aztec" }

4. Define the contract:

use dep::aztec::macros::aztec;

#[aztec]
contract ArrayPublicImmutable {
    use aztec::macros::{functions::{initializer, public}, storage::storage};
    use aztec::prelude::PublicImmutable;

    #[storage]
    struct Storage<Context> {
        state: PublicImmutable<[Field; 3], Context>,
    }

    #[initializer]
    #[public]
    fn initialize(arr: [Field; 3]) {
        storage.state.initialize(arr);
    }
}

5. Compile the contract:

aztec-nargo compile

6. Check the error log.

error: Assertion failed
   ┌─ std/option.nr:33:16
   │
33 │         assert(self._is_some);
   │                -------------
   │
   = Call stack:
[..omitted]
error: Could not resolve 'init' in path
   ┌─ src/main.nr:19:1
   │
19 │ 
   │  
   │

error: Object type is unknown in field access
   ┌─ src/main.nr:16:17
   │
16 │         storage.state.initialize(arr);
   │                 ----- Type must be known by this point
   │
   = Try adding a type annotation for the object type before this expression

Aborting due to 3 previous errors

Expected Behavior

The PublicImmutable Storage struct should seamlessly handle arrays like [Field; 3] without any issues.

Actual Behavior

The program crashes with a panic when trying to use [Field; 3] as the parameter.

Notes

The bug occurs in noir-projects/aztec-nr/aztec/src/macros/utils.nr:227:5. Here, the program tries to compute the serialized size of the element provided as the template parameter, which apparently does not work for arrays.

I implemented a temporary fix for my use case, but someone with more expertise should address this properly.