How should I use rust-analyzer with #[no_core]?

[seancroach]

To address the obligatory elephant in the room, I am aware that #[no_core] is volatile and generally regarded as a bad idea. But it's available to me, and I want to use it. It's been a fun experience so far, but rust-analyzer has a mildly annoying (albeit probably sane) authoritative view on where coherence for primitives live. Consider a very cut-down no_core library:

#![feature(arbitrary_self_types, intrinsics, lang_items, no_core, rustc_attrs)]
#![rustc_coherence_is_core]
#![allow(internal_features)]
#![no_core]

impl u32 {
    fn increment(&self) -> u32 {
        saturating_add(*self, 1)
    }
}

#[unsafe(no_mangle)]
pub extern "C" fn test() -> u32 {
    let x = 12u32;
    x.increment()
}

#[lang = "copy"]
pub trait Copy {}

impl Copy for u32 {}

#[lang = "sized"]
pub trait Sized: MetaSized {}

#[lang = "meta_sized"]
pub trait MetaSized: PointeeSized {}

#[lang = "pointee_sized"]
pub trait PointeeSized {}

#[lang = "freeze"]
pub trait Freeze {}

#[rustc_intrinsic]
pub const fn saturating_add<T: Copy>(a: T, b: T) -> T;

#[lang = "receiver"]
pub trait Receiver: PointeeSized {
    #[lang = "receiver_target"]
    type Target: ?Sized;
}

NOTE: I understand the semantic issues with the traits above. This is just a minimal reproduction anyone could compile and inspect.

Now, I'd expect rust-analyzer to see that this crate has a coherence attribute, then try to resolve the methods in the crate, seeing them as coherent, like rustc does. However, some skimming through rust-analyzer forces the crate to be within the sysroot, somewhat arbitrarily? I know this should be expected to some extent, but my solutions seem to be faking my own sysroot (which seems even worse than what I already want to do) or forking rust-analyzer to remove that check (which I still really do not want to do). I'm hoping someone more familiar with rust-analyzer or the like has some silver bullet that could possibly let me avoid either of those options.

[ChayimFriedman2]

Yes, you will have to fake the sysroot. You might be able to do so by changing rust-analyzer.cargo.sysroot, or you will need to use rust-project.json. We don't support that because that is simpler and more performant to us, and we won't change this to support the perma-unstable #![no_core].

[seancroach]

Makes sense to me! Thanks for the quick reply.