zerocopy_derive/
lib.rs

1// Copyright 2019 The Fuchsia Authors
2//
3// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
4// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
5// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
6// This file may not be copied, modified, or distributed except according to
7// those terms.
8
9//! Derive macros for [zerocopy]'s traits.
10//!
11//! [zerocopy]: https://docs.rs/zerocopy
12
13// Sometimes we want to use lints which were added after our MSRV.
14// `unknown_lints` is `warn` by default and we deny warnings in CI, so without
15// this attribute, any unknown lint would cause a CI failure when testing with
16// our MSRV.
17#![allow(unknown_lints)]
18#![deny(renamed_and_removed_lints)]
19#![deny(
20    clippy::all,
21    clippy::missing_safety_doc,
22    clippy::multiple_unsafe_ops_per_block,
23    clippy::undocumented_unsafe_blocks
24)]
25// We defer to own discretion on type complexity.
26#![allow(clippy::type_complexity)]
27// Inlining format args isn't supported on our MSRV.
28#![allow(clippy::uninlined_format_args)]
29#![deny(
30    rustdoc::bare_urls,
31    rustdoc::broken_intra_doc_links,
32    rustdoc::invalid_codeblock_attributes,
33    rustdoc::invalid_html_tags,
34    rustdoc::invalid_rust_codeblocks,
35    rustdoc::missing_crate_level_docs,
36    rustdoc::private_intra_doc_links
37)]
38#![recursion_limit = "128"]
39
40macro_rules! ident {
41    (($fmt:literal $(, $arg:expr)*), $span:expr) => {
42        syn::Ident::new(&format!($fmt $(, crate::util::to_ident_str($arg))*), $span)
43    };
44}
45
46mod derive;
47#[cfg(test)]
48mod output_tests;
49mod repr;
50mod util;
51
52use syn::{DeriveInput, Error};
53
54use crate::util::*;
55
56// FIXME(https://github.com/rust-lang/rust/issues/54140): Some errors could be
57// made better if we could add multiple lines of error output like this:
58//
59// error: unsupported representation
60//   --> enum.rs:28:8
61//    |
62// 28 | #[repr(transparent)]
63//    |
64// help: required by the derive of FromBytes
65//
66// Instead, we have more verbose error messages like "unsupported representation
67// for deriving FromZeros, FromBytes, IntoBytes, or Unaligned on an enum"
68//
69// This will probably require Span::error
70// (https://doc.rust-lang.org/nightly/proc_macro/struct.Span.html#method.error),
71// which is currently unstable. Revisit this once it's stable.
72
73/// Defines a derive function named `$outer` which parses its input
74/// `TokenStream` as a `DeriveInput` and then invokes the `$inner` function.
75///
76/// Note that the separate `$outer` parameter is required - proc macro functions
77/// are currently required to live at the crate root, and so the caller must
78/// specify the name in order to avoid name collisions.
79macro_rules! derive {
80    ($trait:ident => $outer:ident => $inner:path) => {
81        #[proc_macro_derive($trait, attributes(zerocopy))]
82        pub fn $outer(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
83            let ast = syn::parse_macro_input!(ts as DeriveInput);
84            let ctx = match Ctx::try_from_derive_input(ast) {
85                Ok(ctx) => ctx,
86                Err(e) => return e.into_compile_error().into(),
87            };
88            let ts = $inner(&ctx, Trait::$trait).into_ts();
89            // We wrap in `const_block` as a backstop in case any derive fails
90            // to wrap its output in `const_block` (and thus fails to annotate)
91            // with the full set of `#[allow(...)]` attributes).
92            let ts = const_block([Some(ts)]);
93            #[cfg(test)]
94            crate::util::testutil::check_hygiene(ts.clone());
95            ts.into()
96        }
97    };
98}
99
100trait IntoTokenStream {
101    fn into_ts(self) -> proc_macro2::TokenStream;
102}
103
104impl IntoTokenStream for proc_macro2::TokenStream {
105    fn into_ts(self) -> proc_macro2::TokenStream {
106        self
107    }
108}
109
110impl IntoTokenStream for Result<proc_macro2::TokenStream, Error> {
111    fn into_ts(self) -> proc_macro2::TokenStream {
112        match self {
113            Ok(ts) => ts,
114            Err(err) => err.to_compile_error(),
115        }
116    }
117}
118
119derive!(KnownLayout => derive_known_layout => crate::derive::known_layout::derive);
120derive!(Immutable => derive_immutable => crate::derive::derive_immutable);
121derive!(TryFromBytes => derive_try_from_bytes => crate::derive::try_from_bytes::derive_try_from_bytes);
122derive!(FromZeros => derive_from_zeros => crate::derive::from_bytes::derive_from_zeros);
123derive!(FromBytes => derive_from_bytes => crate::derive::from_bytes::derive_from_bytes);
124derive!(IntoBytes => derive_into_bytes => crate::derive::into_bytes::derive_into_bytes);
125derive!(Unaligned => derive_unaligned => crate::derive::unaligned::derive_unaligned);
126derive!(ByteHash => derive_hash => crate::derive::derive_hash);
127derive!(ByteEq => derive_eq => crate::derive::derive_eq);
128derive!(SplitAt => derive_split_at => crate::derive::derive_split_at);
129
130/// Deprecated: prefer [`FromZeros`] instead.
131#[deprecated(since = "0.8.0", note = "`FromZeroes` was renamed to `FromZeros`")]
132#[doc(hidden)]
133#[proc_macro_derive(FromZeroes)]
134pub fn derive_from_zeroes(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
135    derive_from_zeros(ts)
136}
137
138/// Deprecated: prefer [`IntoBytes`] instead.
139#[deprecated(since = "0.8.0", note = "`AsBytes` was renamed to `IntoBytes`")]
140#[doc(hidden)]
141#[proc_macro_derive(AsBytes)]
142pub fn derive_as_bytes(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
143    derive_into_bytes(ts)
144}
zerocopy_derive/lib.rs

zerocopy_derive/
lib.rs
