Open
Description
openedon Sep 13, 2024
Code
fn main() {
let i_am_sized = String::new();
*i_am_sized = String::new();
}I thought I've had &mut String, not String, so * was unnecessary here.
Because the lvalue has been dereferenced anyway, it caused confusing type error about a type that is not relevant, and assigning to an unsized type that is not at fault here. But the root cause was unexpectedly triggering Deref instead of a dereference on &mut or DerefMut.
Current output
error[E0308]: mismatched types
--> src/main.rs:3:19
|
3 | *i_am_sized = String::new();
| ----------- ^^^^^^^^^^^^^ expected `str`, found `String`
| |
| expected due to the type of this binding
error[E0277]: the size for values of type `str` cannot be known at compilation time
--> src/main.rs:3:5
|
3 | *i_am_sized = String::new();
| ^^^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `str`
Desired output
Something that *i_am_sized due to Deref is can't be assigned to, and suggest removing * instead.
Rust Version
rustc 1.83.0-nightly (8d6b88b16 2024-09-11)
binary: rustc
commit-hash: 8d6b88b168e45ee1624699c19443c49665322a91
commit-date: 2024-09-11
host: aarch64-apple-darwin
release: 1.83.0-nightly
LLVM version: 19.1.0Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment