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author | Benno Lossin <benno.lossin@proton.me> | 2024-03-09 15:53:25 +0000 |
---|---|---|
committer | Miguel Ojeda <ojeda@kernel.org> | 2024-04-07 22:03:42 +0200 |
commit | 9762dca54a4fec433b50eb83fdd8ff0a876cccf2 (patch) | |
tree | 761ac8ee08d70ca7f2e32f9741e699f659a48667 | |
parent | a321f3ad0a5ddcd1da221cc056ef4fd5a49fa0f7 (diff) |
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<$ty_generics> {
fn foo() {
// ...
}
}
}
The next commit contains a fix to the `#[pin_data]` macro making it
compatible with generic parameter default values by relying on this new
behavior.
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240309155243.482334-1-benno.lossin@proton.me
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
-rw-r--r-- | rust/macros/helpers.rs | 123 | ||||
-rw-r--r-- | rust/macros/pin_data.rs | 1 | ||||
-rw-r--r-- | rust/macros/zeroable.rs | 1 |
3 files changed, 95 insertions, 30 deletions
diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs index afb0f2e3a36a..2497d6519f2f 100644 --- a/rust/macros/helpers.rs +++ b/rust/macros/helpers.rs @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 -use proc_macro::{token_stream, Group, Punct, Spacing, TokenStream, TokenTree}; +use proc_macro::{token_stream, Group, TokenStream, TokenTree}; pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> { if let Some(TokenTree::Ident(ident)) = it.next() { @@ -70,8 +70,41 @@ pub(crate) fn expect_end(it: &mut token_stream::IntoIter) { } } +/// Parsed generics. +/// +/// See the field documentation for an explanation what each of the fields represents. +/// +/// # Examples +/// +/// ```rust,ignore +/// # let input = todo!(); +/// let (Generics { decl_generics, impl_generics, ty_generics }, rest) = parse_generics(input); +/// quote! { +/// struct Foo<$($decl_generics)*> { +/// // ... +/// } +/// +/// impl<$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, |