linux/rust
Benno Lossin 960c37cbcb rust: pin-init: properly document let binding workaround
The three let bindings (in the bodies of `cast_init`, `cast_pin_init`
and the `init!` macro) are used to avoid the following compiler error in
Rust 1.78.0, 1.79.0, 1.80.0, 1.80.1, and 1.81.0 (just showing the one
for `cast_init`, the others are similar):

    error[E0391]: cycle detected when computing type of opaque `cast_init::{opaque#0}`
        --> src/lib.rs:1160:66
         |
    1160 | pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> {
         |                                                                  ^^^^^^^^^^^^^^^
         |
    note: ...which requires borrow-checking `cast_init`...
        --> src/lib.rs:1160:1
         |
    1160 | pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> {
         | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    note: ...which requires const checking `cast_init`...
        --> src/lib.rs:1160:1
         |
    1160 | pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> {
         | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
         = note: ...which requires computing whether `cast_init::{opaque#0}` is freeze...
         = note: ...which requires evaluating trait selection obligation `cast_init::{opaque#0}: core::marker::Freeze`...
         = note: ...which again requires computing type of opaque `cast_init::{opaque#0}`, completing the cycle
    note: cycle used when computing type of `cast_init::{opaque#0}`
        --> src/lib.rs:1160:66
         |
    1160 | pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E> {
         |                                                                  ^^^^^^^^^^^^^^^
         = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

Once we raise the nightly-MSRV above 1.81, we can remove this
workaround.

Link: bb3e96f3e9
[ Moved this commit after the previous one to avoid a build failure due
  to unstable features. Changed the cfg to use `USE_RUSTC_FEAUTURES`.
  - Benno ]
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260319093542.3756606-3-lossin@kernel.org
Signed-off-by: Benno Lossin <lossin@kernel.org>
History 2026-03-25 10:56:53 +01:00
..
bindings Char/Misc/IIO driver changes for 7.0-rc1 2026-02-17 09:11:04 -08:00
helpers USB / Thunderbolt changes for 7.0-rc1 2026-02-17 09:36:43 -08:00
kernel Rust fixes for v7.0 (2nd) 2026-03-14 12:35:16 -07:00
macros Rust changes for v6.20 / v7.0 2026-02-10 11:53:01 -08:00
pin-init rust: pin-init: properly document let binding workaround 2026-03-25 10:56:53 +01:00
proc-macro2 rust: proc-macro2: rebuild if the version text changes 2026-01-23 10:44:27 +01:00
quote rust: quote: add README.md 2025-11-24 17:15:43 +01:00
syn rust: syn: add README.md 2025-11-24 17:15:47 +01:00
uapi Char/Misc/IIO/Binder changes for 6.18-rc1 2025-10-04 16:26:32 -07:00
.gitignore rust: support running Rust documentation tests as KUnit ones 2023-07-19 09:32:53 -06:00
.kunitconfig rust: add kunitconfig 2025-03-19 23:22:21 +01:00
bindgen_parameters mm: declare VMA flags by bit 2025-11-29 10:41:08 -08:00
build_error.rs rust: add build_error crate 2022-12-04 01:59:16 +01:00
compiler_builtins.rs ARM: 9441/1: rust: Enable Rust support for ARMv7 2025-03-26 13:31:16 +00:00
exports.c rust: exports: improve grammar in commentary 2024-10-21 17:35:33 +02:00
ffi.rs rust: replace CStr with core::ffi::CStr 2025-10-22 07:47:27 +02:00
Makefile rust: pin-init: build: simplify use of nightly features 2026-03-25 10:56:16 +01:00