`coroutine_clone` causes memory leaks, panics, and UB

I was noticing some memory leaks when I cloned coroutines and managed to turn it into a panic:

#![feature(coroutines, coroutine_trait, coroutine_clone)]
use std::{ops::Coroutine, pin::Pin};

#[derive(Clone)]
enum Foo {
    Bar(Vec<u8>),
}

fn create_coro() -> impl Coroutine<()> + Clone {
    #[coroutine]
    || match Foo::Bar(vec![0_u8]) {
        Foo::Bar(var) => {
            drop(var);
            yield;
        }
    }
}

fn main() {
    let mut coro = create_coro();
    Pin::new(&mut coro).resume(());
    let _ = coro.clone();
}

This code looks reasonable to me but running it returns:

thread 'main' (32000) panicked at C:\Users\zinfo\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib/rustlib/src/rust\library\core\src\ptr\mod.rs:527:5:
unsafe precondition(s) violated: ptr::copy_nonoverlapping requires that both pointer arguments are aligned and non-null and the specified memory ranges do not overlap

This indicates a bug in the program. This Undefined Behavior check is optional, and cannot be relied on for safety.

Meta

rustc --version --verbose:

rustc 1.95.0-nightly (18d13b533 2026-02-09)
binary: rustc
commit-hash: 18d13b5332916ffca8eadb9106d54b5b434e9978
commit-date: 2026-02-09
host: x86_64-pc-windows-msvc
release: 1.95.0-nightly
LLVM version: 22.1.0

stack backtrace:
   0: std::panicking::panic_handler
             at /rustc/18d13b5332916ffca8eadb9106d54b5b434e9978/library\std\src\panicking.rs:689
   1: core::panicking::panic_nounwind_fmt
             at /rustc/18d13b5332916ffca8eadb9106d54b5b434e9978/library\core\src\intrinsics\mod.rs:2434
   2: core::ptr::copy_nonoverlapping::precondition_check
             at C:\Users\zinfo\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\ub_checks.rs:73
   3: alloc::slice::impl$0::to_vec_in::impl$1::to_vec<u8,alloc::alloc::Global>
             at C:\Users\zinfo\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\slice.rs:454
   4: alloc::vec::impl$12::clone<u8,alloc::alloc::Global>
             at C:\Users\zinfo\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\vec\mod.rs:3684
   5: coroutine_tests::impl$0::clone
             at .\src\main.rs:6
   6: core::clone::Clone::clone<enum2$<coroutine_tests::create_coro::coroutine_env$0> >
             at C:\Users\zinfo\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\clone.rs:236
   7: coroutine_tests::main
             at .\src\main.rs:22
   8: core::ops::function::FnOnce::call_once<void (*)(),tuple$<> >
             at C:\Users\zinfo\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\ops\function.rs:250

Start by reproducing the example with the reported nightly toolchain and inspect the coroutine_clone behavior reached from core::clone::Clone::clone. Trace the interaction with alloc::vec::Vec::clone, alloc::slice::to_vec, and core::ptr::copy_nonoverlapping, using the supplied backtrace and src/main.rs example as entry points. Done means cloning the resumed coroutine no longer leaks, panics, or invokes undefined behavior.