Commit 22eed606 authored by Benno Lossin's avatar Benno Lossin Committed by Miguel Ojeda
Browse files

rust: macros: allow generic parameter default values in `#[pin_data]` 



Add support for generic parameters defaults in `#[pin_data]` by using
the newly introduced `decl_generics` instead of the `impl_generics`.

Before this would not compile:

    #[pin_data]
    struct Foo<const N: usize = 0> {
        // ...
    }

because it would be expanded to this:

    struct Foo<const N: usize = 0> {
        // ...
    }

    const _: () = {
        struct __ThePinData<const N: usize = 0> {
            __phantom: ::core::marker::PhantomData<fn(Foo<N>) -> Foo<N>>,
        }
        impl<const N: usize = 0> ::core::clone::Clone for __ThePinData<N> {
            fn clone(&self) -> Self {
                *self
            }
        }

        // [...] rest of expansion omitted
    };

The problem is with the `impl<const N: usize = 0>`, since that is
invalid Rust syntax. It should not mention the default value at all,
since default values only make sense on type definitions.

The new `impl_generics` do not contain the default values, thus
generating correct Rust code.

This is used by the next commit that puts `#[pin_data]` on
`kernel::workqueue::Work`.

Signed-off-by: default avatarBenno Lossin <benno.lossin@proton.me>
Reviewed-by: default avatarMartin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Tested-by: default avatarAlice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240309155243.482334-2-benno.lossin@proton.me


Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 9762dca5

rust/kernel/init/macros.rs

+18 −1
Original line number Diff line number Diff line
@@ -538,6 +538,7 @@ macro_rules! __pin_data { 
        ),

        @impl_generics($($impl_generics:tt)*),

        @ty_generics($($ty_generics:tt)*),

        @decl_generics($($decl_generics:tt)*),

        @body({ $($fields:tt)* }),

    ) => {

        // We now use token munching to iterate through all of the fields. While doing this we
@@ -560,6 +561,9 @@ macro_rules! __pin_data { 
            @impl_generics($($impl_generics)*),

            // The 'ty generics', the generics that will need to be specified on the impl blocks.

            @ty_generics($($ty_generics)*),

            // The 'decl generics', the generics that need to be specified on the struct

            // definition.

            @decl_generics($($decl_generics)*),

            // The where clause of any impl block and the declaration.

            @where($($($whr)*)?),

            // The remaining fields tokens that need to be processed.
@@ -585,6 +589,7 @@ macro_rules! __pin_data { 
        @name($name:ident),

        @impl_generics($($impl_generics:tt)*),

        @ty_generics($($ty_generics:tt)*),

        @decl_generics($($decl_generics:tt)*),

        @where($($whr:tt)*),

        // We found a PhantomPinned field, this should generally be pinned!

        @fields_munch($field:ident : $($($(::)?core::)?marker::)?PhantomPinned, $($rest:tt)*),
@@ -607,6 +612,7 @@ macro_rules! __pin_data { 
            @name($name),

            @impl_generics($($impl_generics)*),

            @ty_generics($($ty_generics)*),

            @decl_generics($($decl_generics)*),

            @where($($whr)*),

            @fields_munch($($rest)*),

            @pinned($($pinned)* $($accum)* $field: ::core::marker::PhantomPinned,),
@@ -623,6 +629,7 @@ macro_rules! __pin_data { 
        @name($name:ident),

        @impl_generics($($impl_generics:tt)*),

        @ty_generics($($ty_generics:tt)*),

        @decl_generics($($decl_generics:tt)*),

        @where($($whr:tt)*),

        // We reached the field declaration.

        @fields_munch($field:ident : $type:ty, $($rest:tt)*),
@@ -640,6 +647,7 @@ macro_rules! __pin_data { 
            @name($name),

            @impl_generics($($impl_generics)*),

            @ty_generics($($ty_generics)*),

            @decl_generics($($decl_generics)*),

            @where($($whr)*),

            @fields_munch($($rest)*),

            @pinned($($pinned)* $($accum)* $field: $type,),
@@ -656,6 +664,7 @@ macro_rules! __pin_data { 
        @name($name:ident),

        @impl_generics($($impl_generics:tt)*),

        @ty_generics($($ty_generics:tt)*),

        @decl_generics($($decl_generics:tt)*),

        @where($($whr:tt)*),

        // We reached the field declaration.

        @fields_munch($field:ident : $type:ty, $($rest:tt)*),
@@ -673,6 +682,7 @@ macro_rules! __pin_data { 
            @name($name),

            @impl_generics($($impl_generics)*),

            @ty_generics($($ty_generics)*),

            @decl_generics($($decl_generics)*),

            @where($($whr)*),

            @fields_munch($($rest)*),

            @pinned($($pinned)*),
@@ -689,6 +699,7 @@ macro_rules! __pin_data { 
        @name($name:ident),

        @impl_generics($($impl_generics:tt)*),

        @ty_generics($($ty_generics:tt)*),

        @decl_generics($($decl_generics:tt)*),

        @where($($whr:tt)*),

        // We found the `#[pin]` attr.

        @fields_munch(#[pin] $($rest:tt)*),
@@ -705,6 +716,7 @@ macro_rules! __pin_data { 
            @name($name),

            @impl_generics($($impl_generics)*),

            @ty_generics($($ty_generics)*),

            @decl_generics($($decl_generics)*),

            @where($($whr)*),

            @fields_munch($($rest)*),

            // We do not include `#[pin]` in the list of attributes, since it is not actually an
@@ -724,6 +736,7 @@ macro_rules! __pin_data { 
        @name($name:ident),

        @impl_generics($($impl_generics:tt)*),

        @ty_generics($($ty_generics:tt)*),

        @decl_generics($($decl_generics:tt)*),

        @where($($whr:tt)*),

        // We reached the field declaration with visibility, for simplicity we only munch the

        // visibility and put it into `$accum`.
@@ -741,6 +754,7 @@ macro_rules! __pin_data { 
            @name($name),

            @impl_generics($($impl_generics)*),

            @ty_generics($($ty_generics)*),

            @decl_generics($($decl_generics)*),

            @where($($whr)*),

            @fields_munch($field $($rest)*),

            @pinned($($pinned)*),
@@ -757,6 +771,7 @@ macro_rules! __pin_data { 
        @name($name:ident),

        @impl_generics($($impl_generics:tt)*),

        @ty_generics($($ty_generics:tt)*),

        @decl_generics($($decl_generics:tt)*),

        @where($($whr:tt)*),

        // Some other attribute, just put it into `$accum`.

        @fields_munch(#[$($attr:tt)*] $($rest:tt)*),
@@ -773,6 +788,7 @@ macro_rules! __pin_data { 
            @name($name),

            @impl_generics($($impl_generics)*),

            @ty_generics($($ty_generics)*),

            @decl_generics($($decl_generics)*),

            @where($($whr)*),

            @fields_munch($($rest)*),

            @pinned($($pinned)*),
@@ -789,6 +805,7 @@ macro_rules! __pin_data { 
        @name($name:ident),

        @impl_generics($($impl_generics:tt)*),

        @ty_generics($($ty_generics:tt)*),

        @decl_generics($($decl_generics:tt)*),

        @where($($whr:tt)*),

        // We reached the end of the fields, plus an optional additional comma, since we added one

        // before and the user is also allowed to put a trailing comma.
@@ -802,7 +819,7 @@ macro_rules! __pin_data { 
    ) => {

        // Declare the struct with all fields in the correct order.

        $($struct_attrs)*

        $vis struct $name <$($impl_generics)*>

        $vis struct $name <$($decl_generics)*>

        where $($whr)*

        {

            $($fields)*

rust/macros/helpers.rs

+0 −1
Original line number Diff line number Diff line
@@ -95,7 +95,6 @@ pub(crate) struct Generics { 
    /// The generics with bounds and default values (e.g. `T: Clone, const N: usize = 0`).

    ///

    /// Use this on type definitions e.g. `struct Foo<$decl_generics> ...` (or `union`/`enum`).

    #[allow(dead_code)]

    pub(crate) decl_generics: Vec<TokenTree>,

    /// The generics with bounds (e.g. `T: Clone, const N: usize`).

    ///

rust/macros/pin_data.rs

+2 −1
Original line number Diff line number Diff line
@@ -10,7 +10,7 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream { 
    let (

        Generics {

            impl_generics,

            decl_generics: _,

            decl_generics,

            ty_generics,

        },

        rest,
@@ -77,6 +77,7 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream { 
        @sig(#(#rest)*),

        @impl_generics(#(#impl_generics)*),

        @ty_generics(#(#ty_generics)*),

        @decl_generics(#(#decl_generics)*),

        @body(#last),

    });

    quoted.extend(errs);