[Rust]: Object API codegen for arrays missing `Default` trait implementation

[pveierland]

When building the following schema using flatc --rust --gen-object-api hash_digest.fbs:

struct HashDigest {
    size: uint8 (id: 0);
    data: [uint8:64] (id: 1);
}

The generated object API rust code is:

#[derive(Debug, Clone, PartialEq, Default)]
pub struct HashDigestT {
  pub size: u8,
  pub data: [u8; 64],
}

This fails to build as there is no implementation of the Default trait for the array:

error[E0277]: the trait bound `[u8; 64]: Default` is not satisfied

This appears to be a bug and the expectation is that the generated code will build given this schema.

Tested with flatc version 25.12.19.

[RenzoMXD]

Hello, @jtdavis777 . May I have a chance to contribute to this issue?
I’d like to contribute to resolving the problem with the missing Default trait implementation for arrays in the generated Rust code. I believe I can help identify the root cause and propose a solution.

[jtdavis777]

Hey for sure! Happy to receive a PR for this.

[RenzoMXD]

#8947 All 21 tests pass, including compilation of the new LargeArrayStructT which would fail with the old codegen.

Files changed

• src/idl_gen_rust.cpp — emit manual impl Default for struct objects
• tests/arrays_test.fbs — added LargeArrayStruct with [ubyte:64]
• tests/arrays_test/arrays_test_generated.rs — regenerated

@jtdavis777 would appreciate your review on this.