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    SubjectRe: [PATCH v4 02/15] rust: macros: add `quote!` macro
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    y86-dev@protonmail.com writes:

    > From: Gary Guo <gary@garyguo.net>
    >
    > Add the `quote!` macro for creating `TokenStream`s directly via the
    > given Rust tokens. It also supports repetitions using iterators.
    >
    > It will be used by the pin-init API proc-macros to generate code.
    >
    > Signed-off-by: Gary Guo <gary@garyguo.net>
    > Signed-off-by: Benno Lossin <y86-dev@protonmail.com>
    > Cc: Alice Ryhl <aliceryhl@google.com>
    > Cc: Andreas Hindborg <a.hindborg@samsung.com>
    > ---

    Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>

    > rust/macros/lib.rs | 2 +
    > rust/macros/quote.rs | 145 +++++++++++++++++++++++++++++++++++++++++++
    > 2 files changed, 147 insertions(+)
    > create mode 100644 rust/macros/quote.rs
    >
    > diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
    > index c1d385e345b9..82b520f024dd 100644
    > --- a/rust/macros/lib.rs
    > +++ b/rust/macros/lib.rs
    > @@ -2,6 +2,8 @@
    >
    > //! Crate for all kernel procedural macros.
    >
    > +#[macro_use]
    > +mod quote;
    > mod concat_idents;
    > mod helpers;
    > mod module;
    > diff --git a/rust/macros/quote.rs b/rust/macros/quote.rs
    > new file mode 100644
    > index 000000000000..94a6277182ee
    > --- /dev/null
    > +++ b/rust/macros/quote.rs
    > @@ -0,0 +1,145 @@
    > +// SPDX-License-Identifier: Apache-2.0 OR MIT
    > +
    > +use proc_macro::{TokenStream, TokenTree};
    > +
    > +pub(crate) trait ToTokens {
    > + fn to_tokens(&self, tokens: &mut TokenStream);
    > +}
    > +
    > +impl<T: ToTokens> ToTokens for Option<T> {
    > + fn to_tokens(&self, tokens: &mut TokenStream) {
    > + if let Some(v) = self {
    > + v.to_tokens(tokens);
    > + }
    > + }
    > +}
    > +
    > +impl ToTokens for proc_macro::Group {
    > + fn to_tokens(&self, tokens: &mut TokenStream) {
    > + tokens.extend([TokenTree::from(self.clone())]);
    > + }
    > +}
    > +
    > +impl ToTokens for TokenTree {
    > + fn to_tokens(&self, tokens: &mut TokenStream) {
    > + tokens.extend([self.clone()]);
    > + }
    > +}
    > +
    > +impl ToTokens for TokenStream {
    > + fn to_tokens(&self, tokens: &mut TokenStream) {
    > + tokens.extend(self.clone());
    > + }
    > +}
    > +
    > +/// Converts tokens into [`proc_macro::TokenStream`] and performs variable interpolations with
    > +/// the given span.
    > +///
    > +/// This is a similar to the
    > +/// [`quote_spanned!`](https://docs.rs/quote/latest/quote/macro.quote_spanned.html) macro from the
    > +/// `quote` crate but provides only just enough functionality needed by the current `macros` crate.
    > +#[allow(unused_macros)]
    > +macro_rules! quote_spanned {
    > + ($span:expr => $($tt:tt)*) => {
    > + #[allow(clippy::vec_init_then_push)]
    > + {
    > + let mut tokens = ::std::vec::Vec::new();
    > + let span = $span;
    > + quote_spanned!(@proc tokens span $($tt)*);
    > + ::proc_macro::TokenStream::from_iter(tokens)
    > + }};
    > + (@proc $v:ident $span:ident) => {};
    > + (@proc $v:ident $span:ident #$id:ident $($tt:tt)*) => {
    > + let mut ts = ::proc_macro::TokenStream::new();
    > + $crate::quote::ToTokens::to_tokens(&$id, &mut ts);
    > + $v.extend(ts);
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident #(#$id:ident)* $($tt:tt)*) => {
    > + for token in $id {
    > + let mut ts = ::proc_macro::TokenStream::new();
    > + $crate::quote::ToTokens::to_tokens(&token, &mut ts);
    > + $v.extend(ts);
    > + }
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident ( $($inner:tt)* ) $($tt:tt)*) => {
    > + let mut tokens = ::std::vec::Vec::new();
    > + quote_spanned!(@proc tokens $span $($inner)*);
    > + $v.push(::proc_macro::TokenTree::Group(::proc_macro::Group::new(
    > + ::proc_macro::Delimiter::Parenthesis,
    > + ::proc_macro::TokenStream::from_iter(tokens)
    > + )));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident [ $($inner:tt)* ] $($tt:tt)*) => {
    > + let mut tokens = ::std::vec::Vec::new();
    > + quote_spanned!(@proc tokens $span $($inner)*);
    > + $v.push(::proc_macro::TokenTree::Group(::proc_macro::Group::new(
    > + ::proc_macro::Delimiter::Bracket,
    > + ::proc_macro::TokenStream::from_iter(tokens)
    > + )));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident { $($inner:tt)* } $($tt:tt)*) => {
    > + let mut tokens = ::std::vec::Vec::new();
    > + quote_spanned!(@proc tokens $span $($inner)*);
    > + $v.push(::proc_macro::TokenTree::Group(::proc_macro::Group::new(
    > + ::proc_macro::Delimiter::Brace,
    > + ::proc_macro::TokenStream::from_iter(tokens)
    > + )));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident :: $($tt:tt)*) => {
    > + $v.push(::proc_macro::TokenTree::Punct(
    > + ::proc_macro::Punct::new(':', ::proc_macro::Spacing::Joint)
    > + ));
    > + $v.push(::proc_macro::TokenTree::Punct(
    > + ::proc_macro::Punct::new(':', ::proc_macro::Spacing::Alone)
    > + ));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident : $($tt:tt)*) => {
    > + $v.push(::proc_macro::TokenTree::Punct(
    > + ::proc_macro::Punct::new(':', ::proc_macro::Spacing::Alone)
    > + ));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident , $($tt:tt)*) => {
    > + $v.push(::proc_macro::TokenTree::Punct(
    > + ::proc_macro::Punct::new(',', ::proc_macro::Spacing::Alone)
    > + ));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident @ $($tt:tt)*) => {
    > + $v.push(::proc_macro::TokenTree::Punct(
    > + ::proc_macro::Punct::new('@', ::proc_macro::Spacing::Alone)
    > + ));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident ! $($tt:tt)*) => {
    > + $v.push(::proc_macro::TokenTree::Punct(
    > + ::proc_macro::Punct::new('!', ::proc_macro::Spacing::Alone)
    > + ));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > + (@proc $v:ident $span:ident $id:ident $($tt:tt)*) => {
    > + $v.push(::proc_macro::TokenTree::Ident(::proc_macro::Ident::new(stringify!($id), $span)));
    > + quote_spanned!(@proc $v $span $($tt)*);
    > + };
    > +}
    > +
    > +/// Converts tokens into [`proc_macro::TokenStream`] and performs variable interpolations with
    > +/// mixed site span ([`Span::mixed_site()`]).
    > +///
    > +/// This is a similar to the [`quote!`](https://docs.rs/quote/latest/quote/macro.quote.html) macro
    > +/// from the `quote` crate but provides only just enough functionality needed by the current
    > +/// `macros` crate.
    > +///
    > +/// [`Span::mixed_site()`]: https://doc.rust-lang.org/proc_macro/struct.Span.html#method.mixed_site
    > +#[allow(unused_macros)]
    > +macro_rules! quote {
    > + ($($tt:tt)*) => {
    > + quote_spanned!(::proc_macro::Span::mixed_site() => $($tt)*)
    > + }
    > +}

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