Compiler overflow error

[xxshady]

error[E0275]: overflow evaluating the requirement `NonNull<arc_btree::seal::ArcBTreeSetNodeInner<stabby::collections::arc_btree::Entry<_, _>, _, true, _>>: Sized`
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`host`)
  = note: required for `FieldPair<NonNull<arc_btree::seal::ArcBTreeSetNodeInner<stabby::collections::arc_btree::Entry<_, _>, _, true, _>>, PhantomData<_>>` to implement `IStable`
  = note: 38 redundant requirements hidden
  = note: required for `ArcBTreeSet<stabby::collections::arc_btree::Entry<_, _>, _, true, _>` to implement `IStable`

reproduction code (UPD: minimized reproduction code)

rustc version: rustc 1.82.0 (f6e511eec 2024-10-15)

[xxshady]

turns out, the reason is this wrong function: https://github.com/xxshady/dylib-reload/blob/6e8c3c46b9f1b17223ffd118a7572c5b8a691d71/host/src/helpers.rs#L13-L18

[xxshady]

hm, this compiles

pub unsafe fn get_stabbied_fn<F: IStable + Copy>(library: &impl StabbyLibrary, name: &str) -> F {
  let symbol = library.get_stabbied(&cstr_bytes(name)).unwrap_or_else(|e| {
    panic!("Failed to get {name} symbol from library");
  });
  *symbol
}

but this does not:

pub unsafe fn get_stabbied_fn(library: &impl StabbyLibrary, name: &str) -> impl IStable + Copy {
  let symbol = library.get_stabbied(&cstr_bytes(name)).unwrap_or_else(|e| {
    panic!("Failed to get {name} symbol from library");
  });
  *symbol
}

so it's somehow related to impl syntax

[xxshady]

replacing impl with a generic fixes this issue: xxshady/dylib-reload@ae7ba3a

[xxshady]

another repro