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android / platform / external / rust / crates / synstructure / 0bb7ba9a378749705475e68629f4087da6202db0
commit0bb7ba9a378749705475e68629f4087da6202db0[log] [tgz]
authorIvan Lozano <ivanlozano@google.com>Fri Jul 19 13:33:03 2024 +0000
committerAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>Fri Jul 19 13:33:03 2024 +0000
tree2db95169c01998b8f004de968c9ed2c36980fdf6
parent6fa5b7e9ae17f05a85cb761a65cd8a9e634dcd13 [diff]
parentc6f654e12ac3228b301d8e74408209b25abe4e8c [diff]
Update module with host_cross_supported am: c6f654e12a

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/synstructure/+/3180114

Change-Id: Ifa48e61111e52eb7c3493f0996ed2b5ed57d22c4
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
tree: 2db95169c01998b8f004de968c9ed2c36980fdf6
  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.