Function opaque_type_cycle_error

fn opaque_type_cycle_error(
    tcx: TyCtxt<'_>,
    opaque_def_id: LocalDefId,
) -> ErrorGuaranteed

Emit an error for recursive opaque types.

If this is a return impl Trait, find the item’s return expressions and point at them. For direct recursion this is enough, but for indirect recursion also point at the last intermediary impl Trait.

If all the return expressions evaluate to !, then we explain that the error will go away after changing it. This can happen when a user uses panic!() or similar as a placeholder.