rust: macros: refactor generics parsing of `#[pin_data]` into its own function
Other macros might also want to parse generics. Additionally this makes
the code easier to read, as the next commit will introduce more code in
`#[pin_data]`. Also add more comments to explain how parsing generics
work.
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Link: https://lore.kernel.org/r/20230424081112.99890-2-benno.lossin@proton.me
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
index b2bdd4d..afb0f2e 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, TokenTree};
+use proc_macro::{token_stream, Group, Punct, Spacing, TokenStream, TokenTree};
pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
if let Some(TokenTree::Ident(ident)) = it.next() {
@@ -69,3 +69,87 @@ pub(crate) fn expect_end(it: &mut token_stream::IntoIter) {
panic!("Expected end");
}
}
+
+pub(crate) struct Generics {
+ pub(crate) impl_generics: Vec<TokenTree>,
+ pub(crate) ty_generics: Vec<TokenTree>,
+}
+
+/// Parses the given `TokenStream` into `Generics` and the rest.
+///
+/// The generics are not present in the rest, but a where clause might remain.
+pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
+ // `impl_generics`, the declared generics with their bounds.
+ let mut impl_generics = vec![];
+ // Only the names of the generics, without any bounds.
+ let mut ty_generics = vec![];
+ // Tokens not related to the generics e.g. the `where` token and definition.
+ let mut rest = vec![];
+ // The current level of `<`.
+ let mut nesting = 0;
+ 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 {
+ match tt.clone() {
+ TokenTree::Punct(p) if p.as_char() == '<' => {
+ if nesting >= 1 {
+ // This is inside of the generics and part of some bound.
+ impl_generics.push(tt);
+ }
+ nesting += 1;
+ }
+ TokenTree::Punct(p) if p.as_char() == '>' => {
+ // This is a parsing error, so we just end it here.
+ if nesting == 0 {
+ break;
+ } else {
+ nesting -= 1;
+ if nesting >= 1 {
+ // We are still inside of the generics and part of some bound.
+ impl_generics.push(tt);
+ }
+ if nesting == 0 {
+ break;
+ }
+ }
+ }
+ tt => {
+ 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);
+ } else if nesting == 0 {
+ // If we haven't entered the generics yet, we still want to keep these tokens.
+ rest.push(tt);
+ }
+ }
+ }
+ }
+ rest.extend(toks);
+ (
+ Generics {
+ impl_generics,
+ ty_generics,
+ },
+ rest,
+ )
+}
diff --git a/rust/macros/pin_data.rs b/rust/macros/pin_data.rs
index 954149d..c593b05 100644
--- a/rust/macros/pin_data.rs
+++ b/rust/macros/pin_data.rs
@@ -1,71 +1,19 @@
// SPDX-License-Identifier: Apache-2.0 OR MIT
-use proc_macro::{Punct, Spacing, TokenStream, TokenTree};
+use crate::helpers::{parse_generics, Generics};
+use proc_macro::TokenStream;
pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
// This proc-macro only does some pre-parsing and then delegates the actual parsing to
// `kernel::__pin_data!`.
- //
- // In here we only collect the generics, since parsing them in declarative macros is very
- // elaborate. We also do not need to analyse their structure, we only need to collect them.
- // `impl_generics`, the declared generics with their bounds.
- let mut impl_generics = vec![];
- // Only the names of the generics, without any bounds.
- let mut ty_generics = vec![];
- // Tokens not related to the generics e.g. the `impl` token.
- let mut rest = vec![];
- // The current level of `<`.
- let mut nesting = 0;
- 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 {
- match tt.clone() {
- TokenTree::Punct(p) if p.as_char() == '<' => {
- if nesting >= 1 {
- impl_generics.push(tt);
- }
- nesting += 1;
- }
- TokenTree::Punct(p) if p.as_char() == '>' => {
- if nesting == 0 {
- break;
- } else {
- nesting -= 1;
- if nesting >= 1 {
- impl_generics.push(tt);
- }
- if nesting == 0 {
- break;
- }
- }
- }
- tt => {
- if nesting == 1 {
- match &tt {
- TokenTree::Ident(i) if i.to_string() == "const" => {}
- TokenTree::Ident(_) if at_start => {
- ty_generics.push(tt.clone());
- ty_generics.push(TokenTree::Punct(Punct::new(',', Spacing::Alone)));
- at_start = false;
- }
- TokenTree::Punct(p) if p.as_char() == ',' => at_start = true,
- TokenTree::Punct(p) if p.as_char() == '\'' && at_start => {
- ty_generics.push(tt.clone());
- }
- _ => {}
- }
- }
- if nesting >= 1 {
- impl_generics.push(tt);
- } else if nesting == 0 {
- rest.push(tt);
- }
- }
- }
- }
- rest.extend(toks);
+ let (
+ Generics {
+ impl_generics,
+ ty_generics,
+ },
+ mut rest,
+ ) = parse_generics(input);
// This should be the body of the struct `{...}`.
let last = rest.pop();
quote!(::kernel::__pin_data! {
