1// SPDX-License-Identifier: GPL-2.0
2
3//! Build-time error.
4//!
5//! This crate provides a [const function][const-functions] `build_error`, which will panic in
6//! compile-time if executed in [const context][const-context], and will cause a build error
7//! if not executed at compile time and the optimizer does not optimise away the call.
8//!
9//! It is used by `build_assert!` in the kernel crate, allowing checking of
10//! conditions that could be checked statically, but could not be enforced in
11//! Rust yet (e.g. perform some checks in [const functions][const-functions], but those
12//! functions could still be called in the runtime).
13//!
14//! For details on constant evaluation in Rust, please see the [Reference][const-eval].
15//!
16//! [const-eval]: https://doc.rust-lang.org/reference/const_eval.html
17//! [const-functions]: https://doc.rust-lang.org/reference/const_eval.html#const-functions
18//! [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
19
20#![no_std]
21
22/// Panics if executed in [const context][const-context], or triggers a build error if not.
23///
24/// [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
25#[inline(never)]
26#[cold]
27#[export_name = "rust_build_error"]
28#[track_caller]
29pub const fn build_error(msg: &'static str) -> ! {
30    panic!("{}", msg);
31}
32