Reborrow `expressionAdjustmentHints` are rarely useful

[9999years]

These inlay hints seem to be unnecessary to me:

This is in an otherwise-unchanged project created with cargo init.

fn a(s: &String) {}

fn main() {
    let s = "".to_owned();
    a(&s)
}

First, "".to_owned() gets adjusted to (&*"").to_owned(). std::borrow::ToOwned::to_owned takes a &self reciever, and "" is of type &'static str, so no reborrow or deref coercion should be needed here.

Then, a(&s) gets annotated as a(&*&s), which is again very strange: s: String and fn a takes a &String parameter, so the exact type requested is being supplied.

Apparently these are reborrow hints. I'd actually like to see when Rust automatically does deref coercion or similar, but reborrows appear to happen on basically every usage of basically every variable, so I don't get much value out of them.

• rust-analyzer 2025-08-11
• rustc 1.88.0 (6b00bc388 2025-06-23)
• Editor: NVIM v0.11.3, built-in LSP client
• Relevant settings: rust-analyzer.inlayHints.expressionAdjustmentHints.enable = "always"

[ChayimFriedman2]

A reborrow does happen there, in rustc as well (it always does), so the inlay hints are correct. Whether they're useful is another question.

[9999years]

OK, thanks for the clarification! New request: a mode for these hints that disables only reborrow hints.

[ChayimFriedman2]

I created #20520 for this.

[9999years]

Wow, thanks!!