Open
Description
rust-analyzer version: rust-analyzer version: 0.3.2353-standalone (37acea8052 2025-03-23)
rustc version: rustc 1.84.1 (e71f9a9a9 2025-01-27)
editor or extension: VSCode with rust-analyzer version 0.3.2353
code snippet to reproduce:
use std::cell::RefCell;
/// This type is covariant:
/// ```
/// use rust_playground::lifetimes::Recursive;
/// fn is_covariant<'long, 'short>(value: Recursive<'long>)
/// where
/// 'long: 'short,
/// {
/// let _: Recursive<'short> = value;
/// }
/// ```
/// and not contravariant:
/// ```compile_fail
/// use rust_playground::lifetimes::Recursive;
/// fn is_contravariant<'long, 'short>(value: Recursive<'short>)
/// where
/// 'long: 'short,
/// {
/// let _: Recursive<'long> = value;
/// }
/// ```
pub struct Recursive<'a> {
v: &'a i32,
parent: Option<Box<Recursive<'a>>>,
}
/// This type is not covariant:
/// ```compile_fail
/// use rust_playground::lifetimes::Recursive1;
/// fn is_covariant<'long, 'short>(value: Recursive1<'long>)
/// where
/// 'long: 'short,
/// {
/// let _: Recursive1<'short> = value;
/// }
/// ```
/// and not contravariant
/// ```compile_fail
/// use rust_playground::lifetimes::Recursive1;
/// fn is_contravariant<'long, 'short>(value: Recursive1<'short>)
/// where
/// 'long: 'short,
/// {
/// let _: Recursive1<'long> = value;
/// }
/// ```
/// i.e. it is invariant
pub struct Recursive1<'a>(&'a i32, Option<Box<Recursive2<'a>>>);
pub struct Recursive2<'a>(RefCell<Recursive1<'a>>);For all three defined structs if I hover over the 'a parameter in VSCode it shows me bivariant although Recursive is covariant and Recursive1 and Recursive2 are invariant over 'a.
This gets worse if for example the invariant structs are used together with other covariant types for example:
pub struct Mixed<'a>(&'a i32, Recursive1<'a>);
In this case when I hover over it, it shows covariant although in fact it is invariant.