| use syn; |
| |
| use usage::{self, UsesLifetimes, UsesTypeParams}; |
| use { |
| FromDeriveInput, FromField, FromGenericParam, FromGenerics, FromMeta, FromTypeParam, |
| FromVariant, Result, |
| }; |
| |
| /// An efficient way of discarding data from a syntax element. |
| /// |
| /// All syntax elements will be successfully read into |
| /// the `Ignored` struct, with all properties discarded. |
| #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)] |
| pub struct Ignored; |
| |
| macro_rules! ignored { |
| ($trayt:ident, $method:ident, $syn:path) => { |
| impl $trayt for Ignored { |
| fn $method(_: &$syn) -> Result<Self> { |
| Ok(Ignored) |
| } |
| } |
| }; |
| } |
| |
| ignored!(FromGenericParam, from_generic_param, syn::GenericParam); |
| ignored!(FromGenerics, from_generics, syn::Generics); |
| ignored!(FromTypeParam, from_type_param, syn::TypeParam); |
| ignored!(FromMeta, from_meta, syn::Meta); |
| ignored!(FromDeriveInput, from_derive_input, syn::DeriveInput); |
| ignored!(FromField, from_field, syn::Field); |
| ignored!(FromVariant, from_variant, syn::Variant); |
| |
| impl UsesTypeParams for Ignored { |
| fn uses_type_params<'a>( |
| &self, |
| _opts: &usage::Options, |
| _: &'a usage::IdentSet, |
| ) -> usage::IdentRefSet<'a> { |
| Default::default() |
| } |
| } |
| |
| impl UsesLifetimes for Ignored { |
| fn uses_lifetimes<'a>( |
| &self, |
| _opts: &usage::Options, |
| _: &'a usage::LifetimeSet, |
| ) -> usage::LifetimeRefSet<'a> { |
| Default::default() |
| } |
| } |