bug: Program creating nested Box panics during compilation

[bmmoore]

Bug Report

Cairo version: 2.7.0-rc.0

Current behavior:
Compiling the code below panics:

thread 'main' panicked at /cargo/registry/src/index.crates.io-6f17d22bba15001f/cairo-lang-sierra-generator-2.7.0-rc.0/src/utils.rs:220:21:
internal error: entered unreachable code: Should be handled by `const_libfunc_id_by_type`.

Expected behavior:

Steps to reproduce:

Compile the code below. I was using scarb build with it as src/lib.cairo.

Related code:

pub enum Pattern { Leaf, Boxed: Box<Pattern> }
pub fn boxed(pat: Pattern) -> Pattern {
    return Pattern::Boxed(BoxTrait::new(pat));
}
pub fn a() -> Pattern { return boxed(Pattern::Leaf); }
pub fn b() -> Pattern { return boxed(a()); }

Other information:

This is quite similar to #5411 and the compile-time example I posted there. The difference is just that the code is split across more functions, and it wasn't fixed by PR #5416.
The workaround described there works, or also just tagging a with #[inline(never)].