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use crate::utils::{add_extra_generic_param, AttrParams, MultiFieldData, State};
use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use syn::{parse::Result, DeriveInput};
/// Provides the hook to expand `#[derive(Into)]` into an implementation of `Into`
pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
let state = State::with_attr_params(
input,
trait_name,
quote!(::core::convert),
trait_name.to_lowercase(),
AttrParams {
enum_: vec!["ignore", "owned", "ref", "ref_mut"],
variant: vec!["ignore", "owned", "ref", "ref_mut"],
struct_: vec!["ignore", "owned", "ref", "ref_mut"],
field: vec!["ignore"],
},
)?;
let MultiFieldData {
variant_info,
field_types,
field_idents,
input_type,
..
} = state.enabled_fields_data();
let mut tokens = TokenStream::new();
for ref_type in variant_info.ref_types() {
let reference = ref_type.reference();
let lifetime = ref_type.lifetime();
let reference_with_lifetime = ref_type.reference_with_lifetime();
let generics_impl;
let (_, ty_generics, where_clause) = input.generics.split_for_impl();
let (impl_generics, _, _) = if ref_type.is_ref() {
generics_impl = add_extra_generic_param(&input.generics, lifetime);
generics_impl.split_for_impl()
} else {
input.generics.split_for_impl()
};
let into = quote! {
impl#impl_generics ::core::convert::From<#reference_with_lifetime #input_type#ty_generics> for
(#(#reference_with_lifetime #field_types),*) #where_clause {
#[allow(unused_variables)]
#[inline]
fn from(original: #reference_with_lifetime #input_type#ty_generics) -> (#(#reference_with_lifetime #field_types),*) {
(#(#reference original.#field_idents),*)
}
}
};
into.to_tokens(&mut tokens);
}
Ok(tokens)
}
|
