No completion for impl blocks on dyn traits

[MaikKlein]

trait Foo {
    fn foo_dyn(&self, s: &str);
}

impl dyn Foo {
    pub fn foo<T: AsRef<str>>(&self, s: T) {
        self.foo_dyn(s.as_ref())
    }
}

impl Foo for u32 {
    fn foo_dyn(&self, s: &str) {
        println!("{} {}", self, s);
    }
}

fn main() {

    let f: Box<dyn Foo> = Box::new(42);
    // No completion for `f.foo`
    f.foo("Hello");
}

There are no completions for functions inside an impl dyn Trait { } block. It is often nice to add generics on top of your trait objects.

Tested in vim and vscode

Language server version 0.2.408 for rust-analyzer

[flodiebold]

I believe the problem may be in this code:

https://github.com/rust-analyzer/rust-analyzer/blob/ef989880fff36f10b7e166647497779bacc1c47f/crates/hir_ty/src/method_resolution.rs#L248-L276

which determines the crates in which inherent impls for a type may be found. Note that it currently doesn't handle Ty::Dyn at all; it probably needs to look at the first trait and take its definition crate.

We probably also need to add a variant to TyFingerprint:

https://github.com/rust-analyzer/rust-analyzer/blob/ef989880fff36f10b7e166647497779bacc1c47f/crates/hir_ty/src/method_resolution.rs#L30-L32

It would probably look something like Dyn(TraitId).

The TraitId can be retrieved using the dyn_trait method on Ty.

[fisherdarling]

I'll try and take this one on!