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android / platform / external / rust / crates / synstructure / refs/tags/android-14.0.0_r75
tag276b76e7edb5012ce1207cf74bf1ed18a2c54d4d
taggerThe Android Open Source Project <initial-contribution@android.com>Tue Nov 12 18:38:29 2024 -0800
object275569d7d4d5c2d9fb2ffa0db98c8e782a175613 
Android 14.0.0 release 75
commit275569d7d4d5c2d9fb2ffa0db98c8e782a175613[log] [tgz]
authorAndrew Walbran <qwandor@google.com>Tue Nov 14 14:25:26 2023 +0000
committerAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>Tue Nov 14 14:25:26 2023 +0000
treeba19dc65d179988d7e4cba1952262efafa233084
parenta597fe051d48ef7b525eb0721a028fdcd30eb673 [diff]
parentfd6693dcfed74a21870f74ba37bd22f10004726b [diff]
Migrate to cargo_embargo. am: 71431fc1f7 am: 77c4925545 am: fd6693dcfe

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/synstructure/+/2828053

Change-Id: I323ca7b4f67dc0ad32e55b3ad575cfee4609adfd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
tree: ba19dc65d179988d7e4cba1952262efafa233084
  1. src/
  2. .cargo_vcs_info.json
  3. Android.bp
  4. Cargo.toml
  5. Cargo.toml.orig
  6. cargo2rulesmk.json
  7. cargo_embargo.json
  8. LICENSE
  9. METADATA
  10. MODULE_LICENSE_MIT
  11. OWNERS
  12. README.md
  13. rules.mk
  14. TEST_MAPPING
README.md

synstructure

Latest Version Documentation Build Status Rustc Version 1.31+

NOTE: What follows is an exerpt from the module level documentation. For full details read the docs on docs.rs

This crate provides helper types for matching against enum variants, and extracting bindings to each of the fields in the deriving Struct or Enum in a generic way.

If you are writing a #[derive] which needs to perform some operation on every field, then you have come to the right place!

Example: WalkFields

Trait Implementation

pub trait WalkFields: std::any::Any {
    fn walk_fields(&self, walk: &mut FnMut(&WalkFields));
}
impl WalkFields for i32 {
    fn walk_fields(&self, _walk: &mut FnMut(&WalkFields)) {}
}

Custom Derive

#[macro_use]
extern crate synstructure;
#[macro_use]
extern crate quote;
extern crate proc_macro2;

fn walkfields_derive(s: synstructure::Structure) -> proc_macro2::TokenStream {
    let body = s.each(|bi| quote!{
        walk(#bi)
    });

    s.bound_impl(quote!(example_traits::WalkFields), quote!{
        fn walk_fields(&self, walk: &mut FnMut(&example_traits::WalkFields)) {
            match *self { #body }
        }
    })
}
decl_derive!([WalkFields] => walkfields_derive);

/*
 * Test Case
 */
fn main() {
    test_derive! {
        walkfields_derive {
            enum A<T> {
                B(i32, T),
                C(i32),
            }
        }
        expands to {
            #[allow(non_upper_case_globals)]
            const _DERIVE_example_traits_WalkFields_FOR_A: () = {
                extern crate example_traits;
                impl<T> example_traits::WalkFields for A<T>
                    where T: example_traits::WalkFields
                {
                    fn walk_fields(&self, walk: &mut FnMut(&example_traits::WalkFields)) {
                        match *self {
                            A::B(ref __binding_0, ref __binding_1,) => {
                                { walk(__binding_0) }
                                { walk(__binding_1) }
                            }
                            A::C(ref __binding_0,) => {
                                { walk(__binding_0) }
                            }
                        }
                    }
                }
            };
        }
    }
}

Example: Interest

Trait Implementation

pub trait Interest {
    fn interesting(&self) -> bool;
}
impl Interest for i32 {
    fn interesting(&self) -> bool { *self > 0 }
}

Custom Derive

#[macro_use]
extern crate synstructure;
#[macro_use]
extern crate quote;
extern crate proc_macro2;

fn interest_derive(mut s: synstructure::Structure) -> proc_macro2::TokenStream {
    let body = s.fold(false, |acc, bi| quote!{
        #acc || example_traits::Interest::interesting(#bi)
    });

    s.bound_impl(quote!(example_traits::Interest), quote!{
        fn interesting(&self) -> bool {
            match *self {
                #body
            }
        }
    })
}
decl_derive!([Interest] => interest_derive);

/*
 * Test Case
 */
fn main() {
    test_derive!{
        interest_derive {
            enum A<T> {
                B(i32, T),
                C(i32),
            }
        }
        expands to {
            #[allow(non_upper_case_globals)]
            const _DERIVE_example_traits_Interest_FOR_A: () = {
                extern crate example_traits;
                impl<T> example_traits::Interest for A<T>
                    where T: example_traits::Interest
                {
                    fn interesting(&self) -> bool {
                        match *self {
                            A::B(ref __binding_0, ref __binding_1,) => {
                                false ||
                                    example_traits::Interest::interesting(__binding_0) ||
                                    example_traits::Interest::interesting(__binding_1)
                            }
                            A::C(ref __binding_0,) => {
                                false ||
                                    example_traits::Interest::interesting(__binding_0)
                            }
                        }
                    }
                }
            };
        }
    }
}

For more example usage, consider investigating the abomonation_derive crate, which makes use of this crate, and is fairly simple.