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Message-ID: <20240309155243.482334-1-benno.lossin@proton.me>
Date: Sat, 09 Mar 2024 15:53:25 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, Alice Ryhl <aliceryhl@...gle.com>, Martin Rodriguez Reboredo <yakoyoku@...il.com>, Asahi Lina <lina@...hilina.net>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/3] rust: macros: add `decl_generics` to `parse_generics()`
The generic parameters on a type definition can specify default values.
Currently `parse_generics()` cannot handle this though. For example when
parsing the following generics:
<T: Clone, const N: usize = 0>
The `impl_generics` will be set to `T: Clone, const N: usize = 0` and
`ty_generics` will be set to `T, N`. Now using the `impl_generics` on an
impl block:
impl<$($impl_generics)*> Foo {}
will result in invalid Rust code, because default values are only
available on type definitions.
Therefore add parsing support for generic parameter default values using
a new kind of generics called `decl_generics` and change the old
behavior of `impl_generics` to not contain the generic parameter default
values.
Now `Generics` has three fields:
- `impl_generics`: the generics with bounds
(e.g. `T: Clone, const N: usize`)
- `decl_generics`: the generics with bounds and default values
(e.g. `T: Clone, const N: usize = 0`)
- `ty_generics`: contains the generics without bounds and without
default values (e.g. `T, N`)
`impl_generics` is designed to be used on `impl<$impl_generics>`,
`decl_generics` for the type definition, so `struct Foo<$decl_generics>`
and `ty_generics` whenever you use the type, so `Foo<$ty_generics>`.
Here is an example that uses all three different types of generics:
let (Generics { decl_generics, impl_generics, ty_generics }, rest) = parse_generics(input);
quote! {
struct Foo<$($decl_generics)*> {
// ...
}
impl<$impl_generics> Foo<$ty_generics> {
fn foo() {
// ...
}
}
}
The next commit contains a fix to the `#[pin_data]` macro making it
compatible with generic parameter default values by relying on this new
behavior.
Signed-off-by: Benno Lossin <benno.lossin@...ton.me>
---
v2 -> v3:
- addressed Gary's nits
- add #[allow(dead_code)] to remove warning
- rebase onto rust-next
v1 -> v2:
- improve documentation and commit message explanation
- add motivation to commit message
v1: https://lore.kernel.org/rust-for-linux/20231125125024.1235933-1-benno.lossin@proton.me/
v2: https://lore.kernel.org/rust-for-linux/20231213220447.3613500-1-benno.lossin@proton.me/
rust/macros/helpers.rs | 123 ++++++++++++++++++++++++++++++----------
rust/macros/pin_data.rs | 1 +
rust/macros/zeroable.rs | 1 +
3 files changed, 95 insertions(+), 30 deletions(-)
diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
index afb0f2e3a36a..2497d6519f2f 100644
--- a/rust/macros/helpers.rs
+++ b/rust/macros/helpers.rs
@@ -1,6 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
-use proc_macro::{token_stream, Group, Punct, Spacing, TokenStream, TokenTree};
+use proc_macro::{token_stream, Group, TokenStream, TokenTree};
pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
if let Some(TokenTree::Ident(ident)) = it.next() {
@@ -70,8 +70,41 @@ pub(crate) fn expect_end(it: &mut token_stream::IntoIter) {
}
}
+/// Parsed generics.
+///
+/// See the field documentation for an explanation what each of the fields represents.
+///
+/// # Examples
+///
+/// ```rust,ignore
+/// # let input = todo!();
+/// let (Generics { decl_generics, impl_generics, ty_generics }, rest) = parse_generics(input);
+/// quote! {
+/// struct Foo<$($decl_generics)*> {
+/// // ...
+/// }
+///
+/// impl<$impl_generics> Foo<$ty_generics> {
+/// fn foo() {
+/// // ...
+/// }
+/// }
+/// }
+/// ```
pub(crate) struct Generics {
+ /// The generics with bounds and default values (e.g. `T: Clone, const N: usize = 0`).
+ ///
+ /// Use this on type definitions e.g. `struct Foo<$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`).
+ ///
+ /// Use this on `impl` blocks e.g. `impl<$impl_generics> Trait for ...`.
pub(crate) impl_generics: Vec<TokenTree>,
+ /// The generics without bounds and without default values (e.g. `T, N`).
+ ///
+ /// Use this when you use the type that is declared with these generics e.g.
+ /// `Foo<$ty_generics>`.
pub(crate) ty_generics: Vec<TokenTree>,
}
@@ -79,6 +112,8 @@ pub(crate) struct Generics {
///
/// The generics are not present in the rest, but a where clause might remain.
pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
+ // The generics with bounds and default values.
+ let mut decl_generics = vec![];
// `impl_generics`, the declared generics with their bounds.
let mut impl_generics = vec![];
// Only the names of the generics, without any bounds.
@@ -90,10 +125,17 @@ pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
let mut toks = input.into_iter();
// If we are at the beginning of a generic parameter.
let mut at_start = true;
- for tt in &mut toks {
+ let mut skip_until_comma = false;
+ while let Some(tt) = toks.next() {
+ if nesting == 1 && matches!(&tt, TokenTree::Punct(p) if p.as_char() == '>') {
+ // Found the end of the generics.
+ break;
+ } else if nesting >= 1 {
+ decl_generics.push(tt.clone());
+ }
match tt.clone() {
TokenTree::Punct(p) if p.as_char() == '<' => {
- if nesting >= 1 {
+ if nesting >= 1 && !skip_until_comma {
// This is inside of the generics and part of some bound.
impl_generics.push(tt);
}
@@ -105,49 +147,70 @@ pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
break;
} else {
nesting -= 1;
- if nesting >= 1 {
+ if nesting >= 1 && !skip_until_comma {
// We are still inside of the generics and part of some bound.
impl_generics.push(tt);
}
- if nesting == 0 {
- break;
- }
}
}
- tt => {
+ TokenTree::Punct(p) if skip_until_comma && p.as_char() == ',' => {
if nesting == 1 {
- // Here depending on the token, it might be a generic variable name.
- match &tt {
- // Ignore const.
- TokenTree::Ident(i) if i.to_string() == "const" => {}
- TokenTree::Ident(_) if at_start => {
- ty_generics.push(tt.clone());
- // We also already push the `,` token, this makes it easier to append
- // generics.
- ty_generics.push(TokenTree::Punct(Punct::new(',', Spacing::Alone)));
- at_start = false;
- }
- TokenTree::Punct(p) if p.as_char() == ',' => at_start = true,
- // Lifetimes begin with `'`.
- TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
- ty_generics.push(tt.clone());
- }
- _ => {}
- }
- }
- if nesting >= 1 {
+ impl_generics.push(tt.clone());
impl_generics.push(tt);
- } else if nesting == 0 {
+ skip_until_comma = false;
+ }
+ }
+ _ if !skip_until_comma => {
+ match nesting {
// If we haven't entered the generics yet, we still want to keep these tokens.
- rest.push(tt);
+ 0 => rest.push(tt),
+ 1 => {
+ // Here depending on the token, it might be a generic variable name.
+ match tt.clone() {
+ TokenTree::Ident(i) if at_start && i.to_string() == "const" => {
+ let Some(name) = toks.next() else {
+ // Parsing error.
+ break;
+ };
+ impl_generics.push(tt);
+ impl_generics.push(name.clone());
+ ty_generics.push(name.clone());
+ decl_generics.push(name);
+ at_start = false;
+ }
+ TokenTree::Ident(_) if at_start => {
+ impl_generics.push(tt.clone());
+ ty_generics.push(tt);
+ at_start = false;
+ }
+ TokenTree::Punct(p) if p.as_char() == ',' => {
+ impl_generics.push(tt.clone());
+ ty_generics.push(tt);
+ at_start = true;
+ }
+ // Lifetimes begin with `'`.
+ TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
+ impl_generics.push(tt.clone());
+ ty_generics.push(tt);
+ }
+ // Generics can have default values, we skip these.
+ TokenTree::Punct(p) if p.as_char() == '=' => {
+ skip_until_comma = true;
+ }
+ _ => impl_generics.push(tt),
+ }
+ }
+ _ => impl_generics.push(tt),
}
}
+ _ => {}
}
}
rest.extend(toks);
(
Generics {
impl_generics,
+ decl_generics,
ty_generics,
},
rest,
diff --git a/rust/macros/pin_data.rs b/rust/macros/pin_data.rs
index 6d58cfda9872..022e68e9720d 100644
--- a/rust/macros/pin_data.rs
+++ b/rust/macros/pin_data.rs
@@ -10,6 +10,7 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
let (
Generics {
impl_generics,
+ decl_generics: _,
ty_generics,
},
rest,
diff --git a/rust/macros/zeroable.rs b/rust/macros/zeroable.rs
index 0d605c46ab3b..cfee2cec18d5 100644
--- a/rust/macros/zeroable.rs
+++ b/rust/macros/zeroable.rs
@@ -7,6 +7,7 @@ pub(crate) fn derive(input: TokenStream) -> TokenStream {
let (
Generics {
impl_generics,
+ decl_generics: _,
ty_generics,
},
mut rest,
base-commit: 768409cff6cc89fe1194da880537a09857b6e4db
--
2.42.0
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