compiler incorrectly suggest converting &x ->&mut x instead of &(mut x) when matching on a &T(T : Copy) #148467
Description
Code
fn myfun(s : &[u32]) {
for &x in s {
while x < 1000 {
x *= 2;
}
println!("{x}")
}
}Current output
error[E0384]: cannot assign twice to immutable variable `x`
--> src/lib.rs:6:13
|
4 | for &x in s {
| - first assignment to `x`
5 | while x < 1000 {
6 | x *= 2;
| ^^^^^^ cannot assign twice to immutable variable
|
help: consider making this binding mutable
|
4 | for &mut x in s {
| +++
help: to modify the original value, take a borrow instead
|
4 | for &ref mut x in s {
| +++++++
For more information about this error, try `rustc --explain E0384`.Desired output
error[E0384]: cannot assign twice to immutable variable `x`
--> src/lib.rs:6:13
|
4 | for &x in s {
| - first assignment to `x`
5 | while x < 1000 {
6 | x *= 2;
| ^^^^^^ cannot assign twice to immutable variable
|
help: consider making this binding mutable
|
4 | for &(mut x) in s {
| ++++ +
help: you cannot modify the original value as it is behind a shared reference. use a different iterating method if you want to do so
For more information about this error, try `rustc --explain E0384`.Rationale and extra context
not sure if the second help i put is that useful, could be reworded or removed.
Other cases
Rust Version
rustc 1.91.0 (f8297e351 2025-10-28)
binary: rustc
commit-hash: f8297e351a40c1439a467bbbb6879088047f50b3
commit-date: 2025-10-28
host: x86_64-pc-windows-msvc
release: 1.91.0
LLVM version: 21.1.2Anything else?
No response