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#![crate_type = "proc-macro"]
#![doc(html_root_url = "https://docs.rs/num-derive/0.1")]
extern crate proc_macro;
extern crate proc_macro2;
#[macro_use]
extern crate quote;
extern crate syn;
use proc_macro::TokenStream;
use proc_macro2::Span;
use syn::{Data, Fields, Ident};
#[proc_macro_derive(FromPrimitive)]
pub fn from_primitive(input: TokenStream) -> TokenStream {
let ast: syn::DeriveInput = syn::parse(input).unwrap();
let name = &ast.ident;
let dummy_const = Ident::new(&format!("_IMPL_NUM_FROM_PRIMITIVE_FOR_{}", name), Span::call_site());
let variants = match ast.data {
Data::Enum(ref data_enum) => &data_enum.variants,
_ => panic!("`FromPrimitive` can be applied only to the enums, {} is not an enum", name)
};
let from_i64_var = quote! { n };
let mut expr = quote! { 0i64 };
let mut offset = 0i64;
let clauses: Vec<_> = variants.iter()
.map(|variant| {
let ident = &variant.ident;
match variant.fields {
Fields::Unit => (),
_ => {
panic!("`FromPrimitive` can be applied only to unitary enums, {}::{} is either struct or tuple", name, ident)
},
}
let discriminant_expr = match variant.discriminant {
Some((_, ref const_expr)) => {
expr = quote! { (#const_expr) as i64 };
offset = 1;
expr.clone()
}
None => {
let tt = quote! { #expr + #offset };
offset += 1;
tt
}
};
quote! {
if #from_i64_var == #discriminant_expr {
Some(#name::#ident)
}
}
})
.collect();
let from_i64_var = if clauses.is_empty() { quote!(_) } else { from_i64_var };
let res = quote! {
#[allow(non_upper_case_globals)]
const #dummy_const: () = {
extern crate num as _num;
impl _num::traits::FromPrimitive for #name {
#[allow(trivial_numeric_casts)]
fn from_i64(#from_i64_var: i64) -> Option<Self> {
#(#clauses else)* {
None
}
}
fn from_u64(n: u64) -> Option<Self> {
Self::from_i64(n as i64)
}
}
};
};
res.into()
}
#[proc_macro_derive(ToPrimitive)]
pub fn to_primitive(input: TokenStream) -> TokenStream {
let ast: syn::DeriveInput = syn::parse(input).unwrap();
let name = &ast.ident;
let dummy_const = Ident::new(&format!("_IMPL_NUM_TO_PRIMITIVE_FOR_{}", name), Span::call_site());
let variants = match ast.data {
Data::Enum(ref data_enum) => &data_enum.variants,
_ => panic!("`ToPrimitive` can be applied only to the enums, {} is not an enum", name)
};
let mut expr = quote! { 0i64 };
let mut offset = 0i64;
let variants: Vec<_> = variants.iter()
.map(|variant| {
let ident = &variant.ident;
match variant.fields {
Fields::Unit => (),
_ => {
panic!("`ToPrimitive` can be applied only to unitary enums, {}::{} is either struct or tuple", name, ident)
},
}
let discriminant_expr = match variant.discriminant {
Some((_, ref const_expr)) => {
expr = quote! { (#const_expr) as i64 };
offset = 1;
expr.clone()
}
None => {
let tt = quote! { #expr + #offset };
offset += 1;
tt
}
};
quote!(#name::#ident => (#discriminant_expr))
})
.collect();
let match_expr = if variants.is_empty() {
quote! {
match *self {}
}
} else {
quote! {
Some(match *self {
#(#variants,)*
})
}
};
let res = quote! {
#[allow(non_upper_case_globals)]
const #dummy_const: () = {
extern crate num as _num;
impl _num::traits::ToPrimitive for #name {
#[allow(trivial_numeric_casts)]
fn to_i64(&self) -> Option<i64> {
#match_expr
}
fn to_u64(&self) -> Option<u64> {
self.to_i64().map(|x| x as u64)
}
}
};
};
res.into()
}