use proc_macro2::TokenStream;
use quote::quote;
use crate::{Data, DeriveTrait, Item, SimpleType, TraitImpl};
pub struct Default;
impl TraitImpl for Default {
fn as_str(&self) -> &'static str {
"Default"
}
fn default_derive_trait(&self) -> DeriveTrait {
DeriveTrait::Default
}
fn build_signature(
&self,
_item: &Item,
_traits: &[DeriveTrait],
_trait_: &DeriveTrait,
body: &TokenStream,
) -> TokenStream {
quote! {
fn default() -> Self {
#body
}
}
}
fn build_body(
&self,
_traits: &[DeriveTrait],
trait_: &DeriveTrait,
data: &Data,
) -> TokenStream {
if data.is_default() {
let path = &data.path;
match data.simple_type() {
SimpleType::Struct(_) => {
let fields = data.iter_field_ident(**trait_);
let trait_path = trait_.path();
quote! { #path { #(#fields: #trait_path::default()),* } }
}
SimpleType::Tuple(_) => {
let trait_path = trait_.path();
let fields = data
.iter_fields(**trait_)
.map(|_| quote! { #trait_path::default() });
quote! { #path(#(#fields),*) }
}
SimpleType::Unit(_) => {
quote! { #path }
}
SimpleType::Union(_) => unreachable!("unexpected trait for union"),
}
}
else {
TokenStream::new()
}
}
}