Closed
Description
Lint name:
clippy::question_mark
I tried this code:
fn might_fail() -> Result<*mut u8, ()> {
todo!();
}
pub fn ptr_stuff() -> *mut u8 {
let ptr = if let Ok(ptr) = might_fail() {
ptr
} else {
return core::ptr::null_mut();
};
unsafe { ptr.offset(1) }
}I expected to see this happen: no warnings.
Instead, this happened:
warning: this if-let-else may be rewritten with the `?` operator
--> src/lib.rs:6:15
|
6 | let ptr = if let Ok(ptr) = might_fail() {
| _______________^
7 | | ptr
8 | | } else {
9 | | return core::ptr::null_mut();
10 | | };
| |_____^ help: replace it with: `might_fail()?`
|
If you try to follow the suggestion that clippy makes, compilation fails:
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::FromResidual`)
--> src/lib.rs:6:27
|
5 | / pub fn ptr_stuff() -> *mut u8 {
6 | | let ptr = might_fail()?;
| | ^ cannot use the `?` operator in a function that returns `*mut u8`
7 | | unsafe { ptr.offset(1) }
8 | | }
| |_- this function should return `Result` or `Option` to accept `?`
|
= help: the trait `std::ops::FromResidual<std::result::Result<std::convert::Infallible, ()>>` is not implemented for `*mut u8`
note: required by `std::ops::FromResidual::from_residual`
--> /home/nicholasbishop/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/try_trait.rs:339:5
|
339 | fn from_residual(residual: R) -> Self;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Meta
Rust version (rustc -Vv):
rustc 1.58.0-nightly (ff0e14829 2021-10-31)
binary: rustc
commit-hash: ff0e14829e1806ca0d4226595f7fdf3e8658758f
commit-date: 2021-10-31
host: x86_64-unknown-linux-gnu
release: 1.58.0-nightly
LLVM version: 13.0.0