False negative for trivial_casts with pointer
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- Dominant language
- Rust
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Description
After #113262, this will no longer fail to compile:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=8ee721b21617d98d18c5256778b57efe
#[deny(trivial_casts)]
fn main() {
let a = std::ptr::null::<()>();
let _b = a as *const ();
}
The cast is trivial, but we miss it because we have to conservatively assume that raw pointer casts are not trivial. A possible fix would be to check for trivial raw pointer casts in MIR (but correctly considering lifetimes is still not quite easy there I think).
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the Rust playground example and trace the trivial_casts lint handling for raw pointer casts. Investigate the proposed MIR check, with particular attention to lifetime correctness; done means the shown cast is diagnosed without misclassifying other raw pointer casts.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100