rust-analyzer: Autocomplete fails on Vec after custom allocators support was added

Description

Autocomplete fails to show any result under specific circumstances:

demo

This problem only seems to happen on rust nightly. It consistently disappears after rustup default stable and restarting the RA server. The bytes crate doesn’t seems to have anything cfg’ed on nightly. Functions in other traits (e.g. std::io::Read) seems to work fine.

Environment

RA: 2020-11-23 (cadf0e9)
VSCode: 1.51.1
Rust: 1.50.0-nightly (1c389ffef 2020-11-24)

Minimal reproducible example

Switch to nightly toolchain
Add bytes = "0.6" to dependencies
Add use bytes::{BytesMut, buf::Buf};
Write let buf = BytesMut::new();
Try to complete on buf.<|>

~~(Verified to be reproducible in Windows Sandbox using a fresh install of Rust, VSCode, and RA without changing any settings)~~

~~This is maybe related to #6612, but I’m not sure because a) it doesn’t complete no matter what I do or how long I wait; and b) it somehow only appears in Rust nightly.~~

Edit: see https://github.com/rust-analyzer/rust-analyzer/issues/6668#issuecomment-735501557

About this issue

Original URL
State: closed
Created 4 years ago
Comments: 16 (16 by maintainers)

Commits related to this issue

Use correct, full substs for self type in impl Without arbitrary self types, the self type could never refer to the method type parameters, so this wasn't a problem; but with arbitrary self types, it... — committed to flodiebold/rust-analyzer by flodiebold 4 years ago
Use correct, full substs for self type in impl Without arbitrary self types, the self type could never refer to the method type parameters, so this wasn't a problem; but with arbitrary self types, it... — committed to flodiebold/rust-analyzer by flodiebold 4 years ago
Merge #6723 6723: Use correct, full substs for self type in impl r=flodiebold a=flodiebold Without arbitrary self types, the self type could never refer to the method type parameters, so this wasn't... — committed to rust-lang/rust-analyzer by bors[bot] 4 years ago
Use correct, full substs for self type in impl Without arbitrary self types, the self type could never refer to the method type parameters, so this wasn't a problem; but with arbitrary self types, it... — committed to Matthias-Fauconneau/rust-analyzer by flodiebold 4 years ago

Most upvoted comments


struct Slice<T> {}
struct Box<T, A> {}
struct Vec<T, A> {}

impl<T> Slice<T> {
    pub fn into_vec<A>(self: Box<Self, A>) -> Vec<T, A> { }
}

fn main() {
    let foo: Slice<u32>;
    foo.
}

reproduces the problem on stable. I’m pretty sure the problem is the second type parameter on the Box.

flodiebold on Dec 4, 2020

For me the latest working version is da3846948 2020-11-21 and it fails on a0d664bae 2020-11-22, so it shouldn’t be the same issue? The only major difference between them appears to be rust-lang/rust#78461.

Oh! I see. BytesMut derefs to Vec<u8>, so that’s why most of the other types don’t have the same issue.

use std::ops::Deref;

fn main() {
    let test = Test { vec: vec![] };
    test.<|>        // Fails to complete
}

struct Test {
    vec: Vec<u8>
}

impl Deref for Test {
    type Target = Vec<u8>;

    fn deref(&self) -> &Self::Target {
        &self.vec
    }
}

andylizi on Nov 30, 2020