`feature(extract_if)` [1] was stabilized in Rust 1.87.0 [2], and the last
significant change happened in Rust 1.85.0 [3] when the range parameter
was added.

That is, with our new minimum version, we can start using the feature.

Thus simplify the code using the feature and remove the TODO comment.

Suggested-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/rust-for-linux/DHHVSX66206Y.3E7I9QUNTCJ8I@garyguo.net/
Link: https://github.com/rust-lang/rust/issues/43244 [1]
Link: https://github.com/rust-lang/rust/pull/137109 [2]
Link: https://github.com/rust-lang/rust/pull/133265 [3]
Link: https://patch.msgid.link/20260405235309.418950-16-ojeda@kernel.org
Reviewed-by: Tamir Duberstein <tamird@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

`clippy::incompatible_msrv` is not buying us much, and we discussed
allowing it several times in the past.

For instance, there was recently another patch sent to `allow` it where
needed [1]. While that particular case would not be needed after the
minimum version bump to 1.85.0, it is simpler to just allow it to prevent
future instances.

[ In addition, the lint fired without taking into account the features
  that have been enabled in a crate [2]. While this was improved in Rust
  1.90.0 [3], it would still fire in a case like this patch. ]

Thus do so, and remove the last instance of locally allowing it we have
in the tree (except the one in the vendored `proc_macro2` crate).

Note that we still keep the `msrv` config option in `clippy.toml` since
that affects other lints as well.

Link: https://lore.kernel.org/rust-for-linux/20260404212831.78971-4-jhubbard@nvidia.com/ [1]
Link: https://github.com/rust-lang/rust-clippy/issues/14425 [2]
Link: https://github.com/rust-lang/rust-clippy/pull/14433 [3]
Link: https://patch.msgid.link/20260405235309.418950-8-ojeda@kernel.org
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Tamir Duberstein <tamird@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Clippy in Rust 1.88.0 (only) reported [1] up to the previous commit:

    warning: variables can be used directly in the `format!` string
       --> rust/macros/module.rs:112:23
        |
    112 |         let content = format!("{param}:{content}", param = param, content = content);
        |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
        = note: `-W clippy::uninlined-format-args` implied by `-W clippy::all`
        = help: to override `-W clippy::all` add `#[allow(clippy::uninlined_format_args)]`
    help: change this to
        |
    112 -         let content = format!("{param}:{content}", param = param, content = content);
    112 +         let content = format!("{param}:{content}");

The reason it only triggers in that version is that the lint was moved
from `pedantic` to `style` in Rust 1.88.0 and then back to `pedantic`
in Rust 1.89.0 [2][3].

In this case, the suggestion is fair and a pure simplification, thus
just apply it.

In addition, do the same for another place in the file that Clippy does
not report because it is multi-line.

Link: https://lore.kernel.org/rust-for-linux/CANiq72=drAtf3y_DZ-2o4jb6Az9J3Yj4QYwWnbRui4sm4AJD3Q@mail.gmail.com/ [1]
Link: https://github.com/rust-lang/rust-clippy/pull/15287 [2]
Link: https://github.com/rust-lang/rust-clippy/issues/15151 [3]
Reviewed-by: Gary Guo <gary@garyguo.net>
Acked-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://patch.msgid.link/20260331205849.498295-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Pull rust updates from Miguel Ojeda:
 "Toolchain and infrastructure:

   - Add '__rust_helper' annotation to the C helpers

     This is needed to inline these helpers into Rust code

   - Remove imports available via the prelude, treewide

     This was possible thanks to a new lint in Klint that Gary has
     implemented -- more Klint-related changes, including initial
     upstream support, are coming

   - Deduplicate pin-init flags

  'kernel' crate:

   - Add support for calling a function exactly once with the new
     'do_once_lite!' macro (and 'OnceLite' type)

     Based on this, add 'pr_*_once!' macros to print only once

   - Add 'impl_flags!' macro for defining common bitflags operations:

         impl_flags!(
             /// Represents multiple permissions.
             #[derive(Debug, Clone, Default, Copy, PartialEq, Eq)]
             pub struct Permissions(u32);

             /// Represents a single permission.
             #[derive(Debug, Clone, Copy, PartialEq, Eq)]
             pub enum Permission {
                 /// Read permission.
                 Read = 1 << 0,

                 /// Write permission.
                 Write = 1 << 1,

                 /// Execute permission.
                 Execute = 1 << 2,
             }
         );

         let mut f: Permissions = Permission::Read | Permission::Write;
         assert!(f.contains(Permission::Read));
         assert!(!f.contains(Permission::Execute));

         f |= Permission::Execute;
         assert!(f.contains(Permission::Execute));

         let f2: Permissions = Permission::Write | Permission::Execute;
         assert!((f ^ f2).contains(Permission::Read));
         assert!(!(f ^ f2).contains(Permission::Write));

   - 'bug' module: support 'CONFIG_DEBUG_BUGVERBOSE_DETAILED' in the
     'warn_on!' macro in order to show the evaluated condition alongside
     the file path:

          ------------[ cut here ]------------
          WARNING: [val == 1] linux/samples/rust/rust_minimal.rs:27 at ...
          Modules linked in: rust_minimal(+)

   - Add safety module with 'unsafe_precondition_assert!' macro,
     currently a wrapper for 'debug_assert!', intended to mark the
     validation of safety preconditions where possible:

         /// # Safety
         ///
         /// The caller must ensure that `index` is less than `N`.
         unsafe fn set_unchecked(&mut self, index: usize, value: T) {
             unsafe_precondition_assert!(
                 index < N,
                 "set_unchecked() requires index ({index}) < N ({N})"
             );

             ...
         }

   - Add instructions to 'build_assert!' documentation requesting to
     always inline functions when used with function arguments

   - 'ptr' module: replace 'build_assert!' with a 'const' one

   - 'rbtree' module: reduce unsafe blocks on pointer derefs

   - 'transmute' module: implement 'FromBytes' and 'AsBytes' for
     inhabited ZSTs, and use it in Nova

   - More treewide replacements of 'c_str!' with C string literals

  'macros' crate:

   - Rewrite most procedural macros ('module!', 'concat_idents!',
     '#[export]', '#[vtable]', '#[kunit_tests]') to use the 'syn'
     parsing library which we introduced last cycle, with better
     diagnostics

     This also allows to support '#[cfg]' properly in the '#[vtable]'
     macro, to support arbitrary types in 'module!' macro (not just an
     identifier) and to remove several custom parsing helpers we had

   - Use 'quote!' from the recently vendored 'quote' library and remove
     our custom one

     The vendored one also allows us to avoid quoting '"' and '{}'
     inside the template anymore and editors can now highlight it. In
     addition, it improves robustness as it eliminates the need for
     string quoting and escaping

   - Use 'pin_init::zeroed()' to simplify KUnit code

  'pin-init' crate:

   - Rewrite all procedural macros ('[pin_]init!', '#[pin_data]',
     '#[pinned_drop]', 'derive([Maybe]Zeroable)') to use the 'syn'
     parsing library which we introduced last cycle, with better
     diagnostics

   - Implement 'InPlaceWrite' for '&'static mut MaybeUninit<T>'. This
     enables users to use external allocation mechanisms such as
     'static_cell'

   - Support tuple structs in 'derive([Maybe]Zeroable)'

   - Support attributes on fields in '[pin_]init!' (such as
     '#[cfg(...)]')

   - Add a '#[default_error(<type>)]' attribute to '[pin_]init!' to
     override the default error (when no '? Error' is specified)

   - Support packed structs in '[pin_]init!' with
     '#[disable_initialized_field_access]'

   - Remove 'try_[pin_]init!' in favor of merging their feature with
     '[pin_]init!'. Update the kernel's own 'try_[pin_]init!' macros to
     use the 'default_error' attribute

   - Correct 'T: Sized' bounds to 'T: ?Sized' in the generated
     'PinnedDrop' check by '#[pin_data]'

  Documentation:

   - Conclude the Rust experiment

  MAINTAINERS:

   - Add "RUST [RUST-ANALYZER]" entry for the rust-analyzer support.
     Tamir and Jesung will take care of it. They have both been active
     around it for a while. The new tree will flow through the Rust one

   - Add Gary as maintainer for "RUST [PIN-INIT]"

   - Update Boqun and Tamir emails to their kernel.org accounts

  And a few other cleanups and improvements"

* tag 'rust-6.20-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: (59 commits)
  rust: safety: introduce `unsafe_precondition_assert!` macro
  rust: add `impl_flags!` macro for defining common bitflag operations
  rust: print: Add pr_*_once macros
  rust: bug: Support DEBUG_BUGVERBOSE_DETAILED option
  rust: print: Add support for calling a function exactly once
  rust: kbuild: deduplicate pin-init flags
  gpu: nova-core: remove imports available via prelude
  rust: clk: replace `kernel::c_str!` with C-Strings
  MAINTAINERS: Update my email address to @kernel.org
  rust: macros: support `#[cfg]` properly in `#[vtable]` macro.
  rust: kunit: use `pin_init::zeroed` instead of custom null value
  rust: macros: rearrange `#[doc(hidden)]` in `module!` macro
  rust: macros: allow arbitrary types to be used in `module!` macro
  rust: macros: convert `#[kunit_tests]` macro to use `syn`
  rust: macros: convert `concat_idents!` to use `syn`
  rust: macros: convert `#[export]` to use `syn`
  rust: macros: use `quote!` for `module!` macro
  rust: macros: use `syn` to parse `module!` macro
  rust: macros: convert `#[vtable]` macro to use `syn`
  rust: macros: use `quote!` from vendored crate
  ...

Currently, we generate `HAS_` constants as long as the definition exists in
the source, regardless if it is cfg-ed out or not.

Currently, uses of `#[cfg]` present in both trait and impl, so it is not a
problem; however if only the impl side uses `#[cfg]` then `HAS_` constants
will incorrectly be true while it shouldnt't.

With `syn` support, we can now implement `#[cfg]` handling properly by
propagating the `#[cfg]` attributes to the constants.

Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://patch.msgid.link/20260113170529.2240744-1-gary@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

The last null element can be created (constly) using `pin_init::zeroed`,
so prefer to use it instead of adding a custom way of building it.

Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: David Gow <davidgow@google.com>
Link: https://patch.msgid.link/20260112170919.1888584-12-gary@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

This `#[doc(hidden)]` can just be applied on a module to hide anything
within.

Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260112170919.1888584-11-gary@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Previously this only accepts an identifier, but now with `syn` it is
easy to make it accepts any type.

Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260112170919.1888584-10-gary@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Make use of `syn` to parse the module structurally and thus improve the
robustness of parsing.

String interpolation is avoided by generating tokens directly using
`quote!`.

Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: David Gow <davidgow@google.com>
Link: https://patch.msgid.link/20260112170919.1888584-9-gary@kernel.org
[ Pass C string to match commit 6c37b6841a92 ("rust: kunit: replace
  `kernel::c_str!` with C-Strings"). - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

This eliminates the need for `expect_punct` helper.

Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260112170919.1888584-8-gary@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>