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use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use syn::Ident;
use crate::{
codegen::{ExtractAttribute, OuterFromImpl, TraitImpl},
options::ForwardAttrs,
util::PathList,
};
/// `impl FromField` generator. This is used for parsing an individual
/// field and its attributes.
pub struct FromFieldImpl<'a> {
pub ident: Option<&'a Ident>,
pub vis: Option<&'a Ident>,
pub ty: Option<&'a Ident>,
pub attrs: Option<&'a Ident>,
pub base: TraitImpl<'a>,
pub attr_names: &'a PathList,
pub forward_attrs: Option<&'a ForwardAttrs>,
pub from_ident: bool,
}
impl<'a> ToTokens for FromFieldImpl<'a> {
fn to_tokens(&self, tokens: &mut TokenStream) {
let input = self.param_name();
let error_declaration = self.base.declare_errors();
let require_fields = self.base.require_fields();
let error_check = self.base.check_errors();
let initializers = self.base.initializers();
let default = if self.from_ident {
quote!(let __default: Self = ::darling::export::From::from(#input.ident.clone());)
} else {
self.base.fallback_decl()
};
let passed_ident = self
.ident
.as_ref()
.map(|i| quote!(#i: #input.ident.clone(),));
let passed_vis = self.vis.as_ref().map(|i| quote!(#i: #input.vis.clone(),));
let passed_ty = self.ty.as_ref().map(|i| quote!(#i: #input.ty.clone(),));
let passed_attrs = self.attrs.as_ref().map(|i| quote!(#i: __fwd_attrs,));
// Determine which attributes to forward (if any).
let grab_attrs = self.extractor();
let post_transform = self.base.post_transform_call();
self.wrap(
quote! {
fn from_field(#input: &::darling::export::syn::Field) -> ::darling::Result<Self> {
#error_declaration
#grab_attrs
#require_fields
#error_check
#default
::darling::export::Ok(Self {
#passed_ident
#passed_ty
#passed_vis
#passed_attrs
#initializers
}) #post_transform
}
},
tokens,
);
}
}
impl<'a> ExtractAttribute for FromFieldImpl<'a> {
fn attr_names(&self) -> &PathList {
self.attr_names
}
fn forwarded_attrs(&self) -> Option<&ForwardAttrs> {
self.forward_attrs
}
fn param_name(&self) -> TokenStream {
quote!(__field)
}
fn core_loop(&self) -> TokenStream {
self.base.core_loop()
}
fn local_declarations(&self) -> TokenStream {
self.base.local_declarations()
}
}
impl<'a> OuterFromImpl<'a> for FromFieldImpl<'a> {
fn trait_path(&self) -> syn::Path {
path!(::darling::FromField)
}
fn trait_bound(&self) -> syn::Path {
path!(::darling::FromMeta)
}
fn base(&'a self) -> &'a TraitImpl<'a> {
&self.base
}
}