delegation: oom

[matthiaskrgr]

Code

#![feature(fn_delegation)]
#![allow(incomplete_features)]

trait Trait<T> {
    fn foo(&self, x: T) -> S { x }
}
struct F;

struct S<T>(F, T);

impl<T, U> Trait<T> for S<U> {
    reuse to_reuse::foo { &self.0 }
}

fn main() {
    let s = S(F, 42);
    assert_eq!(S::<i32>::foo(F, 1), 1);
}

There is no output here, just a lot of action in

  15,52%  librustc_driver-bc351058fafa1e2f.so             [.] rustc_query_impl::execution::collect_active_query_jobs
   9,67%  librustc_driver-bc351058fafa1e2f.so             [.] rustc_query_impl::execution::collect_active_query_jobs_inner::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 16]>>>
   6,45%  librustc_driver-bc351058fafa1e2f.so             [.] rustc_query_impl::execution::collect_active_query_jobs_inner::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 0]>, rustc_middle::dep_graph::graph::DepNodeIndex>>
   3,69%  librustc_driver-bc351058fafa1e2f.so             [.] rustc_query_impl::execution::collect_active_query_jobs_inner::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>>

Meta

rustc --version --verbose:

rustc 1.96.0-nightly (ac7f9ec7d 2026-03-20)
binary: rustc
commit-hash: ac7f9ec7da74d37fd28667c86bf117a39ba5b02a
commit-date: 2026-03-20
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.0

[matthiaskrgr]

another one

#![feature(fn_delegation)]
#![allow(incomplete_features)]

trait Trait {
    fn foo() -> Self::Assoc;
    fn bar(&self) -> u8;
}

impl Trait for u8 {
    fn bar(&self) -> u8 { 1 }
}

struct S(u8);

impl Trait for S {
    reuse Trait::* { &self.0 }
    fn bar(&self) -> u8 { 2 }
}

fn main() {}

[matthiaskrgr]

#![feature(fn_delegation)]
#![allow(incomplete_features)]

trait Trait {
    fn foo(&self) -> Self::Assoc<3> {
        [(); 3]
    }
}

impl () {
    reuse Trait::*;
}

fn main() {}