Code
use std::sync::LazyLock;
static V: LazyLock<(Vec<u8>,)> = LazyLock::new(|| (vec![],));
fn main() {
let (v,) = *V;
let _: &Vec<_> = &v;
}Current output
Compiling playground v0.0.1 (/playground)
error[E0507]: cannot move out of dereference of `LazyLock<(Vec<u8>,)>`
--> src/main.rs:6:16
|
6 | let (v,) = *V;
| - ^^
| |
| data moved here
| move occurs because `v` has type `Vec<u8>`, which does not implement the `Copy` trait
|
help: consider removing the dereference here
|
6 - let (v,) = *V;
6 + let (v,) = V;
|
For more information about this error, try `rustc --explain E0507`.
error: could not compile `playground` (bin "playground") due to 1 previous error
However, after applying this suggestion (*V → V) and recompiling:
Compiling playground v0.0.1 (/playground)
error[E0308]: mismatched types
--> src/main.rs:6:9
|
6 | let (v,) = V;
| ^^^^ - this expression has type `LazyLock<(Vec<u8>,)>`
| |
| expected `LazyLock<(Vec<u8>,)>`, found `(_,)`
|
= note: expected struct `LazyLock<(Vec<u8>,)>`
found tuple `(_,)`
help: consider dereferencing to access the inner value using the Deref trait
|
6 | let (v,) = *V;
| +
For more information about this error, try `rustc --explain E0308`.
error: could not compile `playground` (bin "playground") due to 1 previous errorDesired output
The compiler should provide a consistent and actionable suggestion. For example, it could suggest borrowing instead of moving (e.g., let (v,) = &*V or similar), or otherwise guide the user toward a correct pattern without contradiction.
Rationale and extra context
No response
Other cases
Rust Version
Confirmed on the Playground with the latest versions:
- stable: 1.94.1
- beta: 1.95.0-beta.7 (2026-04-03 cc969f3)
- nightly: 1.96.0-nightly (2026-04-03 2972b5e)
Anything else?
No response
Code
Current output
However, after applying this suggestion (
*V→V) and recompiling:Desired output
The compiler should provide a consistent and actionable suggestion. For example, it could suggest borrowing instead of moving (e.g.,
let (v,) = &*Vor similar), or otherwise guide the user toward a correct pattern without contradiction.Rationale and extra context
No response
Other cases
Rust Version
Confirmed on the Playground with the latest versions:
Anything else?
No response