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use quote::quote;
use syn::parse_macro_input;
use darling::{FromDeriveInput, FromVariant};
#[derive(Debug, FromDeriveInput)]
#[darling(attributes(from), supports(enum_any))]
struct Enum {
ident: syn::Ident,
}
#[derive(Debug, FromVariant)]
#[darling(attributes(from))]
struct EnumField {
ident: syn::Ident,
fields: darling::ast::Fields<syn::Type>,
#[darling(default)]
ignore: bool,
}
pub fn from(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input = parse_macro_input!(input as syn::DeriveInput);
// println!("{:#?}", input);
let network = Enum::from_derive_input(&input).unwrap();
// println!("{:#?}", network);
let enum_name = network.ident;
let fields: Vec<EnumField> = match &input.data {
syn::Data::Enum(data) => data
.variants
.iter()
.map(|field| EnumField::from_variant(field).expect("Could not parse field"))
.collect(),
_ => panic!("from: not an enum"),
};
let derives = fields
.iter()
.filter(|field| !field.fields.fields.is_empty() && !field.ignore)
.map(|field| {
let variant = &field.ident;
let inner_type = &field.fields.fields[0];
quote! {
impl From<#inner_type> for #enum_name {
fn from(input: #inner_type) -> Self {
Self::#variant(input)
}
}
impl std::convert::TryFrom<#enum_name> for #inner_type {
type Error = crate::error::ProtocolError;
fn try_from(input: #enum_name) -> Result<Self, Self::Error> {
match input {
#enum_name::#variant(input) => Ok(input),
_ => Err(crate::error::ProtocolError::WrongVariant),
}
}
}
impl std::convert::TryFrom<&#enum_name> for #inner_type {
type Error = crate::error::ProtocolError;
fn try_from(input: &#enum_name) -> Result<Self, Self::Error> {
match input {
#enum_name::#variant(input) => Ok(input.clone()),
_ => Err(crate::error::ProtocolError::WrongVariant),
}
}
}
}
});
// println!("{:#?}", fields);
let gen = quote! {
#(#derives)*
};
// println!("{}", gen);
gen.into()
}
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