Hovering over constant using slice shows incorrect value

[zeng-y-l]

rust-analyzer version: 0.3.2593-standalone (6b2e677 2025-08-25)

rustc version: rustc 1.88.0 (6b00bc388 2025-06-23)

editor or extension: VSCode 1.105.0, rust-analyzer 0.3.2593

code snippet to reproduce:

const DATA: &[&[u64]] = &[&[42]];

// 0x1000000000000060
const A: u64 = {
    123u64 < 234; // comment out this or the next line, A will be 0
    345u64 < 456;
    let x = DATA[0][0]; // inline x, A will be 456
    x
};

Hover over A (expect 42):

[crypto-priest]

I want to work on this issue. Can you assign it to me?

[ShoyuVanilla]

I want to work on this issue. Can you assign it to me?

You can claim via rustbot command

[crypto-priest]

I've raised a PR #21041

The root cause was that the MIR constant evaluator was reading array index values using a hardcoded pointer size instead of the actual size of the local variable.

[zeng-y-l]

I'm not sure if this issue is about only arrays. I just found out that nested pointers can cause similar problems.

const DATA: &&u64 = &&42;

// 0x1000000000000028
const A: u64 = {
    123u64 < 234;
    let x = **DATA; // inline x, A will be 123
    x
};