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#![recursion_limit = "128"]
extern crate proc_macro;
extern crate syn;
#[macro_use]
extern crate quote;
use proc_macro::TokenStream;
use syn::{DeriveInput, Body, ConstExpr, Lit, VariantData};
#[proc_macro_derive(IntegerId)]
pub fn integer_id(input: TokenStream) -> TokenStream {
let text = input.to_string();
let ast = syn::parse_derive_input(&text).unwrap();
impl_integer_id(&ast).parse().unwrap()
}
#[allow(unused_variables)]
fn impl_integer_id(ast: &DeriveInput) -> quote::Tokens {
let name = &ast.ident;
match ast.body {
Body::Struct(ref data) => {
let fields = data.fields();
match fields.len() {
1 => {
let field = &fields[0];
let field_type = &field.ty;
let (constructor, field_name) = match *data {
VariantData::Struct(_) => {
let field_name = create_tokens(&field.ident);
(quote!(#name { #field_name: value }), field_name)
},
VariantData::Tuple(_) => (quote! { #name( value ) }, quote!(0)),
VariantData::Unit => unreachable!()
};
quote! {
impl ::idmap::IntegerId for #name {
#[inline(always)]
fn from_id(id: u64) -> Self {
let value = <#field_type as ::idmap::IntegerId>::from_id(id);
#constructor
}
#[inline(always)]
fn id(&self) -> u64 {
<#field_type as ::idmap::IntegerId>::id(&self.#field_name)
}
#[inline(always)]
fn id32(&self) -> u32 {
<#field_type as ::idmap::IntegerId>::id32(&self.#field_name)
}
}
}
},
0 => panic!("`IntegerId` is currently unimplemented for empty structs"),
_ => panic!("`IntegerId` can only be applied to structs with a single field, but {} has {}", name, fields.len())
}
},
Body::Enum(ref variants) => {
let mut idx = 0;
let variants: Vec<_> = variants.iter().map(|variant| {
let ident = &variant.ident;
match variant.data {
VariantData::Unit => (),
_ => {
panic!("`IntegerId` can be applied only to unitary enums, {}::{} is either struct or tuple", name, ident)
},
}
match variant.discriminant {
Some(ConstExpr::Lit(Lit::Int(value, _))) => idx = value,
Some(_) => panic!("Can't handle discriminant for {}::{}", name, ident),
None => {}
}
let tt = quote!(#idx => #name::#ident);
idx += 1;
tt
}).collect();
quote! {
impl ::idmap::IntegerId for #name {
#[inline]
fn from_id(id: u64) -> Self {
match id {
#(#variants,)*
_ => ::idmap::_invalid_id(id)
}
}
#[inline(always)]
fn id(&self) -> u64 {
*self as u64
}
#[inline(always)]
fn id32(&self) -> u32 {
*self as u32
}
}
}
}
}
}
#[inline]
fn create_tokens<T: quote::ToTokens>(value: &T) -> quote::Tokens {
let mut result = quote::Tokens::new();
value.to_tokens(&mut result);
result
}