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#![recursion_limit = "128"]
extern crate proc_macro;
extern crate proc_macro2;
#[macro_use]
extern crate quote;
extern crate syn;
use std::iter;
use syn::{Data, DataEnum, DeriveInput, Fields, Ident, Variant};
fn generate_enum_code(name: Ident, data_enum: DataEnum) -> proc_macro2::TokenStream {
let enum_count = data_enum.variants.len();
let mut has_discriminants = false;
for &Variant {
ref fields,
ref discriminant,
..
} in &data_enum.variants
{
match *fields {
Fields::Unit => (),
_ => return quote!(compile_error! {"#[derive(EnumMap)] requires C style style enum"}),
}
if discriminant.is_some() {
has_discriminants = true;
}
}
let variants_names_a = data_enum.variants.iter().map(|variant| &variant.ident);
let variants_names_b = data_enum.variants.iter().map(|variant| &variant.ident);
let repeat_name_a = iter::repeat(&name);
let repeat_name_b = repeat_name_a.clone();
let counter = 0..enum_count;
let to_usize = if enum_count == 0 || has_discriminants {
let variants_names = data_enum.variants.iter().map(|variant| &variant.ident);
let repeat_name = repeat_name_a.clone();
let counter = counter.clone();
quote! {
match self {
#(
#repeat_name::#variants_names => #counter,
)*
}
}
} else {
quote! { self as usize }
};
quote! {
#[automatically_derived]
impl<V> ::enum_map::Enum<V> for #name {
type Array = [V; #enum_count];
const POSSIBLE_VALUES: usize = #enum_count;
#[inline]
fn slice(array: &Self::Array) -> &[V] {
array
}
#[inline]
fn slice_mut(array: &mut Self::Array) -> &mut [V] {
array
}
#[inline]
fn from_usize(value: usize) -> Self {
match value {
#(
#counter => #repeat_name_a::#variants_names_a,
)*
_ => unreachable!()
}
}
#[inline]
fn to_usize(self) -> usize {
#to_usize
}
#[inline]
fn from_function<F: FnMut(Self) -> V>(mut _f: F) -> Self::Array {
[#(
_f(#repeat_name_b::#variants_names_b),
)*]
}
}
}
}
#[proc_macro_derive(Enum)]
pub fn derive_enum_map(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input: DeriveInput = syn::parse(input).unwrap();
let result = match input.data {
Data::Enum(data_enum) => generate_enum_code(input.ident, data_enum),
_ => quote!(compile_error! {"#[derive(EnumMap)] is only defined for enums"}),
};
result.into()
}