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Description
I tried this code:
#![allow(unused)]
#![deny(clippy::missing_const_for_fn)]
struct Buffer {
content: Vec<u8>,
}
impl Buffer {
pub fn content(&self) -> &[u8] {
&self.content
}
}I expected to see this happen: No clippy errors
Instead, this happened:
error: this could be a `const fn`
--> src/lib.rs:8:5
|
8 | / pub fn content(&self) -> &[u8] {
9 | | &self.content
10 | | }
| |_____^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#missing_const_for_fn
note: the lint level is defined here
--> src/lib.rs:2:9
|
2 | #![deny(clippy::missing_const_for_fn)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: make the function `const`
|
8 | pub const fn content(&self) -> &[u8] {
| +++++
Changing the code as suggested gives a compiler error:
❯ cargo check
Checking test-missing-const-for-fn v0.1.0 (/Users/joshka/local/test-missing-const-for-fn)
error[E0015]: cannot perform non-const deref coercion on `Vec<u8>` in constant functions
--> src/lib.rs:9:9
|
9 | &self.content
| ^^^^^^^^^^^^^
|
= note: attempting to deref into `[u8]`
note: deref defined here
--> /Users/joshka/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:3262:5
|
3262 | type Target = [T];
| ^^^^^^^^^^^
note: impl defined here, but it is not `const`
--> /Users/joshka/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:3261:1
|
3261 | impl<T, A: Allocator> ops::Deref for Vec<T, A> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
For more information about this error, try `rustc --explain E0015`.
error: could not compile `test-missing-const-for-fn` (lib) due to 1 previous error
Meta
In beta the clippy error does not show:
rustc --version --verbose:
rustc 1.86.0 (05f9846f8 2025-03-31)
binary: rustc
commit-hash: 05f9846f893b09a1be1fc8560e33fc3c815cfecb
commit-date: 2025-03-31
host: aarch64-apple-darwin
release: 1.86.0
LLVM version: 19.1.7
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