bug: Program creating Nullable<Box<u32>> panics during execution

[fmoletta]

Bug Report

Cairo version: v2.6.3 (Commit 2203a47)

Current behavior:
Running the cairo program in the Related Code section using cairo-run returns panics with:

thread 'main' panicked at crates/cairo-lang-sierra-generator/src/utils.rs:212:21:
internal error: entered unreachable code: Should be handled by `const_libfunc_id_by_type`.

Expected behavior:

The program should run like it used to in v2.5.4, returning :
Run completed successfully, returning [10]

Steps to reproduce:

Create a file with the code in the Related Code section and run it using:
cargo run --bin cairo-run -- --single-file program.cairo

Related code:

fn main() -> Nullable<Box<u32>> {
    nullable_from_box(BoxTrait::new(BoxTrait::new(16)))
}

Other information:

[fmoletta]

Small Update: Running the same program using NullableTrait::new instead of nullable_from_box directly also yields the same error:

use core::nullable::NullableTrait;

fn main() -> Nullable<Box<u32>> {
    NullableTrait::<Box<u32>>::new(BoxTrait::new(16))
}

thread 'main' panicked at crates/cairo-lang-sierra-generator/src/utils.rs:212:21:
internal error: entered unreachable code: Should be handled by `const_libfunc_id_by_type`

[orizi]

thanks for reporting.
Attached PR fixes it. Can be handled locally for the time being by change the code to any of these:

/// The helper
#[inline(never)]
fn identity<T>(t: T) -> T { t }
...
NullableTrait::<Box<u32>>::new(BoxTrait::new(identity(16)))
NullableTrait::<Box<u32>>::new(identity(BoxTrait::new(16)))

[bmmoore]

In case anyone else runs into it, this error can also be seen at compile time - and is fixed in 2.7.0-rc0. Here is minimized code where we were seeing the same internal error during scarb build (with asdf-installed scarb 2.6.5)

pub enum Pattern { Leaf, Boxed: Box<Pattern>, }
pub fn cbox(subpattern: Pattern) -> Pattern {
    return Pattern::Boxed(BoxTrait::new(subpattern));
}
pub fn fail() -> Pattern {
     return cbox(cbox(Pattern::Leaf));
}

   Compiling ml_checker_cairo v0.1.0 (/home/brandon/code/proof-checker-public/cairo/Scarb.toml)
thread 'main' panicked at /cargo/registry/src/index.crates.io-6f17d22bba15001f/cairo-lang-sierra-generator-2.6.4/src/utils.rs:212:21:
internal error: entered unreachable code: Should be handled by `const_libfunc_id_by_type`.
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace