Compiler Hang Issue when Using the iso_un_option Function

[iamanonymouscs]

cat hang.rs

pub type ISO<A: 'static, B: 'static> = (Box<dyn Fn(A) -> B>, Box<dyn Fn(B) -> A>);
pub fn iso<A: 'static, B: 'static, F1, F2>(a: F1, b: F2) -> ISO<A, B>
where
    F1: 'static + Fn(A) -> B,
    F2: 'static + Fn(B) -> A,
{
    (Box::new(a), Box::new(b))
}
pub fn iso_un_option<A: 'static, B: 'static>(i: ISO<Option<A>, Option<B>>) -> ISO<A, B> {
    let (ab, ba) = (i.ab, i.ba);
    let left = move |o_a| match o_a {
        None => panic!("absured"),
        Some(a) => a,
    };
    let right = move |o_b| match o_b {
        None => panic!("absurd"),
        Some(b) => b,
    };
    iso(left, right)
}
pub fn iso_un_option<A: 'static, B: 'static>(i: ISO<Option<A>, B>) -> ISO<A, B> {
    let (ab, ba) = (i.ab, i.ba);
    let left = move |o_a| match o_a {
        None => panic!("absured"),
        Some(a) => a,
    };
    let right = move |o_b| match o_b {
        None => panic!("absurd"),
        Some(b) => b,
    };
    iso(left, right)
}

I expected to see this happen: The compiler compiles successfully or outputs an error message.

Instead, this happened: The code, as provided below, appears to encounter a hang

Command

rustc hang.rs

Meta

rustc --version --verbose:

rustc 1.73.0 (cc66ad468 2023-10-03)
binary: rustc
commit-hash: cc66ad468955717ab92600c770da8c1601a4ff33
commit-date: 2023-10-03
host: x86_64-unknown-linux-gnu
release: 1.73.0
LLVM version: 17.0.2

The same problem is reproduced on the nightly version(1.75.0-nightly 1c05d50c8 2023-10-21)

what's more, to get more information,I also tried '-Z time-passes' (using nighly version):

Output

time:   0.001; rss:   28MB ->   31MB (   +2MB)  parse_crate
error[E0428]: the name `iso_un_option` is defined multiple times
  --> hang.rs:21:1
   |
9  | pub fn iso_un_option<A: 'static, B: 'static>(i: ISO<Option<A>, Option<B>>) -> ISO<A, B> {
   | --------------------------------------------------------------------------------------- previous definition of the value `iso_un_option` here
...
21 | pub fn iso_un_option<A: 'static, B: 'static>(i: ISO<Option<A>, B>) -> ISO<A, B> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `iso_un_option` redefined here
   |
   = note: `iso_un_option` must be defined only once in the value namespace of this module

time:   0.008; rss:   34MB ->   50MB (  +16MB)  expand_crate
time:   0.008; rss:   34MB ->   50MB (  +16MB)  macro_expand_crate
time:   0.001; rss:   50MB ->   53MB (   +3MB)  late_resolve_crate
time:   0.002; rss:   50MB ->   53MB (   +3MB)  resolve_crate
error[E0601]: `main` function not found in crate `hang`
  --> hang.rs:32:2
   |
32 | }
   |  ^ consider adding a `main` function to `hang.rs`

time:   0.007; rss:   53MB ->   59MB (   +6MB)  looking_for_entry_point
time:   0.007; rss:   53MB ->   60MB (   +7MB)  misc_checking_1
time:   0.002; rss:   60MB ->   66MB (   +6MB)  wf_checking
error[E0609]: no field `ab` on type `(Box<(dyn Fn(Option<A>) -> Option<B> + 'static)>, Box<(dyn Fn(Option<B>) -> Option<A> + 'static)>)`
  --> hang.rs:10:23
   |
10 |     let (ab, ba) = (i.ab, i.ba);
   |                       ^^

error[E0609]: no field `ba` on type `(Box<(dyn Fn(Option<A>) -> Option<B> + 'static)>, Box<(dyn Fn(Option<B>) -> Option<A> + 'static)>)`
  --> hang.rs:10:29
   |
10 |     let (ab, ba) = (i.ab, i.ba);
   |                     

[matthewjasper]

Smaller version that should only have a cycle/overflow error, but instead hangs

use std::ptr;

pub type ISO<A, B> = (Box<dyn Fn(A) -> B>, Box<dyn Fn(B) -> A>);
pub fn iso<A: 'static, B: 'static, F1, F2>(a: F1, b: F2) -> ISO<A, B>
where
    F1: 'static + Fn(A) -> B,
    F2: 'static + Fn(B) -> A,
{
    (Box::new(a), Box::new(b))
}

pub fn iso_un_option<A: 'static, B: 'static>() {
    let left = |o_a| unsafe { ptr::read(o_a) };
    let right = |o_b| unsafe { ptr::read(o_b) };
    //~^ ERROR mismatched types
    iso(left, right);
}