Closed
Description
openedon Sep 26, 2022
Summary
In egui crate the TextEdit widget constructor signature is as follows:
pub fn singleline(text: &'t mut dyn TextBuffer) -> Self {
Self {
desired_height_rows: 1,
multiline: false,
..Self::multiline(text)
}
}TextBuffer is implemented as modifiable for String and as non-modifiable for &'_ str.
I want to have modifiable text buffer but in my project I have to use indirection to use singleline method. Clippy seems to trigger false positive for my use case, as changing &mut String to &mut str doesn't even compile. I'm attaching reproductible example below. Playground link: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=fec4899f9c23ecbb68c8e49aca409782
Lint Name
ptr_arg
Reproducer
I tried this code:
use std::marker::PhantomData;
trait DoAThing {
fn a_thing(&mut self);
}
impl<'a> DoAThing for &'a str {
fn a_thing(&mut self) {
todo!()
}
}
impl DoAThing for String {
fn a_thing(&mut self) {
todo!()
}
}
struct Create<'t> {
_phantom: PhantomData<&'t ()>,
}
impl<'t> Create<'t> {
fn a_method(thing: &'t mut dyn DoAThing) -> Self {
thing.a_thing();
Self {
_phantom: Default::default(),
}
}
}
fn external_attempt(src: &mut String) {
Create::a_method(src);
}
fn main() {
}I saw this happen:
warning: writing `&mut String` instead of `&mut str` involves a new object where a slice will do
--> src/main.rs:32:26
|
32 | fn external_attempt(src: &mut String) {
| ^^^^^^^^^^^ help: change this to: `&mut str`
|
= note: `#[warn(clippy::ptr_arg)]` on by default
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_arg
I expected this to compile without warnings.
Version
rustc 1.63.0 (4b91a6ea7 2022-08-08)
binary: rustc
commit-hash: 4b91a6ea7258a947e59c6522cd5898e7c0a6a88f
commit-date: 2022-08-08
host: x86_64-unknown-linux-gnu
release: 1.63.0
LLVM version: 14.0.5
Additional Labels
No response
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