DynMetadata nightly feature breaks RA type inference

[lukesandberg]

rust-analyzer version:
rust-analyzer version: 1.89.0-nightly (59aa1e87 2025-06-03)

rustc version:
rustc 1.89.0-nightly (59aa1e873 2025-06-03)

editor or extension:
VSCode:
Identifier
rust-lang.rust-analyzer
Version
0.3.2490
Last Updated
2025-06-09, 10:06:56

relevant settings:

repository link (if public, optional):
We ran into this as part of a large in flight PR this commit demonstrates our workaround

code snippet to reproduce:

This is a minimal repro for the issue afaict.

We are adopting the nightly feature ptr_metadata and observed that certain type constraints appears to greatly confuse Rust-Analyzer

fn make<T>(_thin: *const (), _meta: std::ptr::DynMetadata<T>) -> *const T
where
    T: std::ptr::Pointee<Metadata = std::ptr::DynMetadata<T>> + ?Sized,
{
    todo!()
}
trait Foo {
    fn foo(&self) -> String {
        todo!()
    }
}

fn test() -> String {
    struct F {}
    impl Foo for F {}
    let meta = std::ptr::metadata(std::ptr::null::<F>() as *const dyn Foo);

    let f = F {};
    let fat_ptr = make(&f as *const F as *const (), meta);  // <-- infers type as `*const {unknown}`

    let fat_ref = unsafe { &*fat_ptr };  // <-- infers type as `&{unknown}`
    fat_ref.foo()  // cannot 'go to definition' on `foo` 
}

Rust Analyzer failed to understand the types of this program. DynMetadata appears to be the problem since RA cannot understand how to perform inference on it.

[ChayimFriedman2]

True, Chalk doesn't properly implement Pointee (https://github.com/rust-lang/chalk/blob/a0ebd5da3ab8c9d46c35c5b3a60016b1fe4996d8/chalk-solve/src/clauses/builtin_traits/pointee.rs#L112-L113). This won't be fixed until we switch to the new trait solver (hopefully soon).