bytemuck_derive/
lib.rs

1//! Derive macros for [bytemuck](https://docs.rs/bytemuck) traits.
2
3extern crate proc_macro;
4
5mod traits;
6
7use proc_macro2::TokenStream;
8use quote::quote;
9use syn::{parse_macro_input, DeriveInput, Result};
10
11use crate::traits::{
12  bytemuck_crate_name, AnyBitPattern, CheckedBitPattern, Contiguous, Derivable,
13  NoUninit, Pod, TransparentWrapper, Zeroable,
14};
15
16/// Derive the `Pod` trait for a struct
17///
18/// The macro ensures that the struct follows all the the safety requirements
19/// for the `Pod` trait.
20///
21/// The following constraints need to be satisfied for the macro to succeed
22///
23/// - All fields in the struct must implement `Pod`
24/// - The struct must be `#[repr(C)]` or `#[repr(transparent)]`
25/// - The struct must not contain any padding bytes
26/// - The struct contains no generic parameters, if it is not
27///   `#[repr(transparent)]`
28///
29/// ## Examples
30///
31/// ```rust
32/// # use std::marker::PhantomData;
33/// # use bytemuck_derive::{Pod, Zeroable};
34/// #[derive(Copy, Clone, Pod, Zeroable)]
35/// #[repr(C)]
36/// struct Test {
37///   a: u16,
38///   b: u16,
39/// }
40///
41/// #[derive(Copy, Clone, Pod, Zeroable)]
42/// #[repr(transparent)]
43/// struct Generic<A, B> {
44///   a: A,
45///   b: PhantomData<B>,
46/// }
47/// ```
48///
49/// If the struct is generic, it must be `#[repr(transparent)]` also.
50///
51/// ```compile_fail
52/// # use bytemuck::{Pod, Zeroable};
53/// # use std::marker::PhantomData;
54/// #[derive(Copy, Clone, Pod, Zeroable)]
55/// #[repr(C)] // must be `#[repr(transparent)]`
56/// struct Generic<A> {
57///   a: A,
58/// }
59/// ```
60///
61/// If the struct is generic and `#[repr(transparent)]`, then it is only `Pod`
62/// when all of its generics are `Pod`, not just its fields.
63///
64/// ```
65/// # use bytemuck::{Pod, Zeroable};
66/// # use std::marker::PhantomData;
67/// #[derive(Copy, Clone, Pod, Zeroable)]
68/// #[repr(transparent)]
69/// struct Generic<A, B> {
70///   a: A,
71///   b: PhantomData<B>,
72/// }
73///
74/// let _: u32 = bytemuck::cast(Generic { a: 4u32, b: PhantomData::<u32> });
75/// ```
76///
77/// ```compile_fail
78/// # use bytemuck::{Pod, Zeroable};
79/// # use std::marker::PhantomData;
80/// # #[derive(Copy, Clone, Pod, Zeroable)]
81/// # #[repr(transparent)]
82/// # struct Generic<A, B> {
83/// #   a: A,
84/// #   b: PhantomData<B>,
85/// # }
86/// struct NotPod;
87///
88/// let _: u32 = bytemuck::cast(Generic { a: 4u32, b: PhantomData::<NotPod> });
89/// ```
90#[proc_macro_derive(Pod, attributes(bytemuck))]
91pub fn derive_pod(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
92  let expanded =
93    derive_marker_trait::<Pod>(parse_macro_input!(input as DeriveInput));
94
95  proc_macro::TokenStream::from(expanded)
96}
97
98/// Derive the `AnyBitPattern` trait for a struct
99///
100/// The macro ensures that the struct follows all the the safety requirements
101/// for the `AnyBitPattern` trait.
102///
103/// The following constraints need to be satisfied for the macro to succeed
104///
105/// - All fields in the struct must to implement `AnyBitPattern`
106#[proc_macro_derive(AnyBitPattern, attributes(bytemuck))]
107pub fn derive_anybitpattern(
108  input: proc_macro::TokenStream,
109) -> proc_macro::TokenStream {
110  let expanded = derive_marker_trait::<AnyBitPattern>(parse_macro_input!(
111    input as DeriveInput
112  ));
113
114  proc_macro::TokenStream::from(expanded)
115}
116
117/// Derive the `Zeroable` trait for a type.
118///
119/// The macro ensures that the type follows all the the safety requirements
120/// for the `Zeroable` trait.
121///
122/// The following constraints need to be satisfied for the macro to succeed on a
123/// struct:
124///
125/// - All fields in the struct must implement `Zeroable`
126///
127/// The following constraints need to be satisfied for the macro to succeed on
128/// an enum:
129///
130/// - The enum has an explicit `#[repr(Int)]`, `#[repr(C)]`, or `#[repr(C,
131///   Int)]`.
132/// - The enum has a variant with discriminant 0 (explicitly or implicitly).
133/// - All fields in the variant with discriminant 0 (if any) must implement
134///   `Zeroable`
135///
136/// The macro always succeeds on unions.
137///
138/// ## Example
139///
140/// ```rust
141/// # use bytemuck_derive::{Zeroable};
142/// #[derive(Copy, Clone, Zeroable)]
143/// #[repr(C)]
144/// struct Test {
145///   a: u16,
146///   b: u16,
147/// }
148/// ```
149/// ```rust
150/// # use bytemuck_derive::{Zeroable};
151/// #[derive(Copy, Clone, Zeroable)]
152/// #[repr(i32)]
153/// enum Values {
154///   A = 0,
155///   B = 1,
156///   C = 2,
157/// }
158/// #[derive(Clone, Zeroable)]
159/// #[repr(C)]
160/// enum Implicit {
161///   A(bool, u8, char),
162///   B(String),
163///   C(std::num::NonZeroU8),
164/// }
165/// ```
166///
167/// # Custom bounds
168///
169/// Custom bounds for the derived `Zeroable` impl can be given using the
170/// `#[zeroable(bound = "")]` helper attribute.
171///
172/// Using this attribute additionally opts-in to "perfect derive" semantics,
173/// where instead of adding bounds for each generic type parameter, bounds are
174/// added for each field's type.
175///
176/// ## Examples
177///
178/// ```rust
179/// # use bytemuck::Zeroable;
180/// # use std::marker::PhantomData;
181/// #[derive(Clone, Zeroable)]
182/// #[zeroable(bound = "")]
183/// struct AlwaysZeroable<T> {
184///   a: PhantomData<T>,
185/// }
186///
187/// AlwaysZeroable::<std::num::NonZeroU8>::zeroed();
188/// ```
189/// ```rust
190/// # use bytemuck::{Zeroable};
191/// #[derive(Copy, Clone, Zeroable)]
192/// #[repr(u8)]
193/// #[zeroable(bound = "")]
194/// enum MyOption<T> {
195///   None,
196///   Some(T),
197/// }
198///
199/// assert!(matches!(MyOption::<std::num::NonZeroU8>::zeroed(), MyOption::None));
200/// ```
201///
202/// ```rust,compile_fail
203/// # use bytemuck::Zeroable;
204/// # use std::marker::PhantomData;
205/// #[derive(Clone, Zeroable)]
206/// #[zeroable(bound = "T: Copy")]
207/// struct ZeroableWhenTIsCopy<T> {
208///   a: PhantomData<T>,
209/// }
210///
211/// ZeroableWhenTIsCopy::<String>::zeroed();
212/// ```
213///
214/// The restriction that all fields must be Zeroable is still applied, and this
215/// is enforced using the mentioned "perfect derive" semantics.
216///
217/// ```rust
218/// # use bytemuck::Zeroable;
219/// #[derive(Clone, Zeroable)]
220/// #[zeroable(bound = "")]
221/// struct ZeroableWhenTIsZeroable<T> {
222///   a: T,
223/// }
224/// ZeroableWhenTIsZeroable::<u32>::zeroed();
225/// ```
226///
227/// ```rust,compile_fail
228/// # use bytemuck::Zeroable;
229/// # #[derive(Clone, Zeroable)]
230/// # #[zeroable(bound = "")]
231/// # struct ZeroableWhenTIsZeroable<T> {
232/// #   a: T,
233/// # }
234/// ZeroableWhenTIsZeroable::<String>::zeroed();
235/// ```
236#[proc_macro_derive(Zeroable, attributes(bytemuck, zeroable))]
237pub fn derive_zeroable(
238  input: proc_macro::TokenStream,
239) -> proc_macro::TokenStream {
240  let expanded =
241    derive_marker_trait::<Zeroable>(parse_macro_input!(input as DeriveInput));
242
243  proc_macro::TokenStream::from(expanded)
244}
245
246/// Derive the `NoUninit` trait for a struct or enum
247///
248/// The macro ensures that the type follows all the the safety requirements
249/// for the `NoUninit` trait.
250///
251/// The following constraints need to be satisfied for the macro to succeed
252/// (the rest of the constraints are guaranteed by the `NoUninit` subtrait
253/// bounds, i.e. the type must be `Sized + Copy + 'static`):
254///
255/// If applied to a struct:
256/// - All fields in the struct must implement `NoUninit`
257/// - The struct must be `#[repr(C)]` or `#[repr(transparent)]`
258/// - The struct must not contain any padding bytes
259/// - The struct must contain no generic parameters
260///
261/// If applied to an enum:
262/// - The enum must be explicit `#[repr(Int)]`, `#[repr(C)]`, or both
263/// - All variants must be fieldless
264/// - The enum must contain no generic parameters
265#[proc_macro_derive(NoUninit, attributes(bytemuck))]
266pub fn derive_no_uninit(
267  input: proc_macro::TokenStream,
268) -> proc_macro::TokenStream {
269  let expanded =
270    derive_marker_trait::<NoUninit>(parse_macro_input!(input as DeriveInput));
271
272  proc_macro::TokenStream::from(expanded)
273}
274
275/// Derive the `CheckedBitPattern` trait for a struct or enum.
276///
277/// The macro ensures that the type follows all the the safety requirements
278/// for the `CheckedBitPattern` trait and derives the required `Bits` type
279/// definition and `is_valid_bit_pattern` method for the type automatically.
280///
281/// The following constraints need to be satisfied for the macro to succeed:
282///
283/// If applied to a struct:
284/// - All fields must implement `CheckedBitPattern`
285/// - The struct must be `#[repr(C)]` or `#[repr(transparent)]`
286/// - The struct must contain no generic parameters
287///
288/// If applied to an enum:
289/// - The enum must be explicit `#[repr(Int)]`
290/// - All fields in variants must implement `CheckedBitPattern`
291/// - The enum must contain no generic parameters
292#[proc_macro_derive(CheckedBitPattern)]
293pub fn derive_maybe_pod(
294  input: proc_macro::TokenStream,
295) -> proc_macro::TokenStream {
296  let expanded = derive_marker_trait::<CheckedBitPattern>(parse_macro_input!(
297    input as DeriveInput
298  ));
299
300  proc_macro::TokenStream::from(expanded)
301}
302
303/// Derive the `TransparentWrapper` trait for a struct
304///
305/// The macro ensures that the struct follows all the the safety requirements
306/// for the `TransparentWrapper` trait.
307///
308/// The following constraints need to be satisfied for the macro to succeed
309///
310/// - The struct must be `#[repr(transparent)]`
311/// - The struct must contain the `Wrapped` type
312/// - Any ZST fields must be [`Zeroable`][derive@Zeroable].
313///
314/// If the struct only contains a single field, the `Wrapped` type will
315/// automatically be determined. If there is more then one field in the struct,
316/// you need to specify the `Wrapped` type using `#[transparent(T)]`
317///
318/// ## Examples
319///
320/// ```rust
321/// # use bytemuck_derive::TransparentWrapper;
322/// # use std::marker::PhantomData;
323/// #[derive(Copy, Clone, TransparentWrapper)]
324/// #[repr(transparent)]
325/// #[transparent(u16)]
326/// struct Test<T> {
327///   inner: u16,
328///   extra: PhantomData<T>,
329/// }
330/// ```
331///
332/// If the struct contains more than one field, the `Wrapped` type must be
333/// explicitly specified.
334///
335/// ```rust,compile_fail
336/// # use bytemuck_derive::TransparentWrapper;
337/// # use std::marker::PhantomData;
338/// #[derive(Copy, Clone, TransparentWrapper)]
339/// #[repr(transparent)]
340/// // missing `#[transparent(u16)]`
341/// struct Test<T> {
342///   inner: u16,
343///   extra: PhantomData<T>,
344/// }
345/// ```
346///
347/// Any ZST fields must be `Zeroable`.
348///
349/// ```rust,compile_fail
350/// # use bytemuck_derive::TransparentWrapper;
351/// # use std::marker::PhantomData;
352/// struct NonTransparentSafeZST;
353///
354/// #[derive(TransparentWrapper)]
355/// #[repr(transparent)]
356/// #[transparent(u16)]
357/// struct Test<T> {
358///   inner: u16,
359///   extra: PhantomData<T>,
360///   another_extra: NonTransparentSafeZST, // not `Zeroable`
361/// }
362/// ```
363#[proc_macro_derive(TransparentWrapper, attributes(bytemuck, transparent))]
364pub fn derive_transparent(
365  input: proc_macro::TokenStream,
366) -> proc_macro::TokenStream {
367  let expanded = derive_marker_trait::<TransparentWrapper>(parse_macro_input!(
368    input as DeriveInput
369  ));
370
371  proc_macro::TokenStream::from(expanded)
372}
373
374/// Derive the `Contiguous` trait for an enum
375///
376/// The macro ensures that the enum follows all the the safety requirements
377/// for the `Contiguous` trait.
378///
379/// The following constraints need to be satisfied for the macro to succeed
380///
381/// - The enum must be `#[repr(Int)]`
382/// - The enum must be fieldless
383/// - The enum discriminants must form a contiguous range
384///
385/// ## Example
386///
387/// ```rust
388/// # use bytemuck_derive::{Contiguous};
389///
390/// #[derive(Copy, Clone, Contiguous)]
391/// #[repr(u8)]
392/// enum Test {
393///   A = 0,
394///   B = 1,
395///   C = 2,
396/// }
397/// ```
398#[proc_macro_derive(Contiguous)]
399pub fn derive_contiguous(
400  input: proc_macro::TokenStream,
401) -> proc_macro::TokenStream {
402  let expanded =
403    derive_marker_trait::<Contiguous>(parse_macro_input!(input as DeriveInput));
404
405  proc_macro::TokenStream::from(expanded)
406}
407
408/// Derive the `PartialEq` and `Eq` trait for a type
409///
410/// The macro implements `PartialEq` and `Eq` by casting both sides of the
411/// comparison to a byte slice and then compares those.
412///
413/// ## Warning
414///
415/// Since this implements a byte wise comparison, the behavior of floating point
416/// numbers does not match their usual comparison behavior. Additionally other
417/// custom comparison behaviors of the individual fields are also ignored. This
418/// also does not implement `StructuralPartialEq` / `StructuralEq` like
419/// `PartialEq` / `Eq` would. This means you can't pattern match on the values.
420///
421/// ## Examples
422///
423/// ```rust
424/// # use bytemuck_derive::{ByteEq, NoUninit};
425/// #[derive(Copy, Clone, NoUninit, ByteEq)]
426/// #[repr(C)]
427/// struct Test {
428///   a: u32,
429///   b: char,
430///   c: f32,
431/// }
432/// ```
433///
434/// ```rust
435/// # use bytemuck_derive::ByteEq;
436/// # use bytemuck::NoUninit;
437/// #[derive(Copy, Clone, ByteEq)]
438/// #[repr(C)]
439/// struct Test<const N: usize> {
440///   a: [u32; N],
441/// }
442/// unsafe impl<const N: usize> NoUninit for Test<N> {}
443/// ```
444#[proc_macro_derive(ByteEq)]
445pub fn derive_byte_eq(
446  input: proc_macro::TokenStream,
447) -> proc_macro::TokenStream {
448  let input = parse_macro_input!(input as DeriveInput);
449  let crate_name = bytemuck_crate_name(&input);
450  let ident = input.ident;
451  let (impl_generics, ty_generics, where_clause) =
452    input.generics.split_for_impl();
453
454  proc_macro::TokenStream::from(quote! {
455    impl #impl_generics ::core::cmp::PartialEq for #ident #ty_generics #where_clause {
456      #[inline]
457      #[must_use]
458      fn eq(&self, other: &Self) -> bool {
459        #crate_name::bytes_of(self) == #crate_name::bytes_of(other)
460      }
461    }
462    impl #impl_generics ::core::cmp::Eq for #ident #ty_generics #where_clause { }
463  })
464}
465
466/// Derive the `Hash` trait for a type
467///
468/// The macro implements `Hash` by casting the value to a byte slice and hashing
469/// that.
470///
471/// ## Warning
472///
473/// The hash does not match the standard library's `Hash` derive.
474///
475/// ## Examples
476///
477/// ```rust
478/// # use bytemuck_derive::{ByteHash, NoUninit};
479/// #[derive(Copy, Clone, NoUninit, ByteHash)]
480/// #[repr(C)]
481/// struct Test {
482///   a: u32,
483///   b: char,
484///   c: f32,
485/// }
486/// ```
487///
488/// ```rust
489/// # use bytemuck_derive::ByteHash;
490/// # use bytemuck::NoUninit;
491/// #[derive(Copy, Clone, ByteHash)]
492/// #[repr(C)]
493/// struct Test<const N: usize> {
494///   a: [u32; N],
495/// }
496/// unsafe impl<const N: usize> NoUninit for Test<N> {}
497/// ```
498#[proc_macro_derive(ByteHash)]
499pub fn derive_byte_hash(
500  input: proc_macro::TokenStream,
501) -> proc_macro::TokenStream {
502  let input = parse_macro_input!(input as DeriveInput);
503  let crate_name = bytemuck_crate_name(&input);
504  let ident = input.ident;
505  let (impl_generics, ty_generics, where_clause) =
506    input.generics.split_for_impl();
507
508  proc_macro::TokenStream::from(quote! {
509    impl #impl_generics ::core::hash::Hash for #ident #ty_generics #where_clause {
510      #[inline]
511      fn hash<H: ::core::hash::Hasher>(&self, state: &mut H) {
512        ::core::hash::Hash::hash_slice(#crate_name::bytes_of(self), state)
513      }
514
515      #[inline]
516      fn hash_slice<H: ::core::hash::Hasher>(data: &[Self], state: &mut H) {
517        ::core::hash::Hash::hash_slice(#crate_name::cast_slice::<_, u8>(data), state)
518      }
519    }
520  })
521}
522
523/// Basic wrapper for error handling
524fn derive_marker_trait<Trait: Derivable>(input: DeriveInput) -> TokenStream {
525  derive_marker_trait_inner::<Trait>(input)
526    .unwrap_or_else(|err| err.into_compile_error())
527}
528
529/// Find `#[name(key = "value")]` helper attributes on the struct, and return
530/// their `"value"`s parsed with `parser`.
531///
532/// Returns an error if any attributes with the given `name` do not match the
533/// expected format. Returns `Ok([])` if no attributes with `name` are found.
534fn find_and_parse_helper_attributes<P: syn::parse::Parser + Copy>(
535  attributes: &[syn::Attribute], name: &str, key: &str, parser: P,
536  example_value: &str, invalid_value_msg: &str,
537) -> Result<Vec<P::Output>> {
538  let invalid_format_msg =
539    format!("{name} attribute must be `{name}({key} = \"{example_value}\")`",);
540  let values_to_check = attributes.iter().filter_map(|attr| match &attr.meta {
541    // If a `Path` matches our `name`, return an error, else ignore it.
542    // e.g. `#[zeroable]`
543    syn::Meta::Path(path) => path
544      .is_ident(name)
545      .then(|| Err(syn::Error::new_spanned(path, &invalid_format_msg))),
546    // If a `NameValue` matches our `name`, return an error, else ignore it.
547    // e.g. `#[zeroable = "hello"]`
548    syn::Meta::NameValue(namevalue) => {
549      namevalue.path.is_ident(name).then(|| {
550        Err(syn::Error::new_spanned(&namevalue.path, &invalid_format_msg))
551      })
552    }
553    // If a `List` matches our `name`, match its contents to our format, else
554    // ignore it. If its contents match our format, return the value, else
555    // return an error.
556    syn::Meta::List(list) => list.path.is_ident(name).then(|| {
557      let namevalue: syn::MetaNameValue = syn::parse2(list.tokens.clone())
558        .map_err(|_| {
559          syn::Error::new_spanned(&list.tokens, &invalid_format_msg)
560        })?;
561      if namevalue.path.is_ident(key) {
562        match namevalue.value {
563          syn::Expr::Lit(syn::ExprLit {
564            lit: syn::Lit::Str(strlit), ..
565          }) => Ok(strlit),
566          _ => {
567            Err(syn::Error::new_spanned(&namevalue.path, &invalid_format_msg))
568          }
569        }
570      } else {
571        Err(syn::Error::new_spanned(&namevalue.path, &invalid_format_msg))
572      }
573    }),
574  });
575  // Parse each value found with the given parser, and return them if no errors
576  // occur.
577  values_to_check
578    .map(|lit| {
579      let lit = lit?;
580      lit.parse_with(parser).map_err(|err| {
581        syn::Error::new_spanned(&lit, format!("{invalid_value_msg}: {err}"))
582      })
583    })
584    .collect()
585}
586
587fn derive_marker_trait_inner<Trait: Derivable>(
588  mut input: DeriveInput,
589) -> Result<TokenStream> {
590  let crate_name = bytemuck_crate_name(&input);
591  let trait_ = Trait::ident(&input, &crate_name)?;
592  // If this trait allows explicit bounds, and any explicit bounds were given,
593  // then use those explicit bounds. Else, apply the default bounds (bound
594  // each generic type on this trait).
595  if let Some(name) = Trait::explicit_bounds_attribute_name() {
596    // See if any explicit bounds were given in attributes.
597    let explicit_bounds = find_and_parse_helper_attributes(
598      &input.attrs,
599      name,
600      "bound",
601      <syn::punctuated::Punctuated<syn::WherePredicate, syn::Token![,]>>::parse_terminated,
602      "Type: Trait",
603      "invalid where predicate",
604    )?;
605
606    if !explicit_bounds.is_empty() {
607      // Explicit bounds were given.
608      // Enforce explicitly given bounds, and emit "perfect derive" (i.e. add
609      // bounds for each field's type).
610      let explicit_bounds = explicit_bounds
611        .into_iter()
612        .flatten()
613        .collect::<Vec<syn::WherePredicate>>();
614
615      let fields = match (Trait::perfect_derive_fields(&input), &input.data) {
616        (Some(fields), _) => fields,
617        (None, syn::Data::Struct(syn::DataStruct { fields, .. })) => {
618          fields.clone()
619        }
620        (None, syn::Data::Union(_)) => {
621          return Err(syn::Error::new_spanned(
622            trait_,
623            &"perfect derive is not supported for unions",
624          ));
625        }
626        (None, syn::Data::Enum(_)) => {
627          return Err(syn::Error::new_spanned(
628            trait_,
629            &"perfect derive is not supported for enums",
630          ));
631        }
632      };
633
634      let predicates = &mut input.generics.make_where_clause().predicates;
635
636      predicates.extend(explicit_bounds);
637
638      for field in fields {
639        let ty = field.ty;
640        predicates.push(syn::parse_quote!(
641          #ty: #trait_
642        ));
643      }
644    } else {
645      // No explicit bounds were given.
646      // Enforce trait bound on all type generics.
647      add_trait_marker(&mut input.generics, &trait_);
648    }
649  } else {
650    // This trait does not allow explicit bounds.
651    // Enforce trait bound on all type generics.
652    add_trait_marker(&mut input.generics, &trait_);
653  }
654
655  let name = &input.ident;
656
657  let (impl_generics, ty_generics, where_clause) =
658    input.generics.split_for_impl();
659
660  Trait::check_attributes(&input.data, &input.attrs)?;
661  let asserts = Trait::asserts(&input, &crate_name)?;
662  let (trait_impl_extras, trait_impl) = Trait::trait_impl(&input, &crate_name)?;
663
664  let implies_trait = if let Some(implies_trait) =
665    Trait::implies_trait(&crate_name)
666  {
667    quote!(unsafe impl #impl_generics #implies_trait for #name #ty_generics #where_clause {})
668  } else {
669    quote!()
670  };
671
672  let where_clause =
673    if Trait::requires_where_clause() { where_clause } else { None };
674
675  Ok(quote! {
676    #asserts
677
678    #trait_impl_extras
679
680    unsafe impl #impl_generics #trait_ for #name #ty_generics #where_clause {
681      #trait_impl
682    }
683
684    #implies_trait
685  })
686}
687
688/// Add a trait marker to the generics if it is not already present
689fn add_trait_marker(generics: &mut syn::Generics, trait_name: &syn::Path) {
690  // Get each generic type parameter.
691  let type_params = generics
692    .type_params()
693    .map(|param| &param.ident)
694    .map(|param| {
695      syn::parse_quote!(
696        #param: #trait_name
697      )
698    })
699    .collect::<Vec<syn::WherePredicate>>();
700
701  generics.make_where_clause().predicates.extend(type_params);
702}
bytemuck_derive/lib.rs

bytemuck_derive/
lib.rs
