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Handle enum discriminants for C-style enums. #3

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bf252cf
Handle enum discriminants for C-style enums.
khuey Aug 27, 2017
3146a3c
Upgrade to latest proc macro stuff.
khuey Jan 28, 2020
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5 changes: 3 additions & 2 deletions enum_index_derive/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,9 @@ homepage = "https://github.com/regresscheck/enum_index"
readme = "../README.md"

[dependencies]
syn = "0.11.11"
quote = "0.3.15"
syn = "1"
proc-macro2 = "1"
quote = "1"

[lib]
proc-macro = true
62 changes: 34 additions & 28 deletions enum_index_derive/src/lib.rs
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Expand Up @@ -2,44 +2,44 @@ extern crate syn;
#[macro_use]
extern crate quote;
extern crate proc_macro;
use proc_macro::TokenStream;
extern crate proc_macro2;
use quote::format_ident;
use syn::{parse_macro_input, DeriveInput};

#[proc_macro_derive(EnumIndex)]
pub fn enum_index(input: TokenStream) -> TokenStream {
let s = input.to_string();
let ast = syn::parse_derive_input(&s).unwrap();
pub fn enum_index(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = parse_macro_input!(input as DeriveInput);

let tokens = impl_enum_index(&ast);
tokens.parse().unwrap()
proc_macro::TokenStream::from(tokens)
}


fn impl_enum_index(ast: &syn::DeriveInput) -> quote::Tokens {
fn impl_enum_index(ast: &syn::DeriveInput) -> proc_macro2::TokenStream {
let name = &ast.ident;
let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();

let variants = match ast.body {
syn::Body::Enum(ref v) => v,
let variants = match ast.data {
syn::Data::Enum(ref v) => &v.variants,
_ => panic!("EnumIndex can be only implemented for Enums")
};

let mut matches = Vec::new();

for variant in variants {
use syn::VariantData::*;
use syn::Fields::*;
let ident = &variant.ident;

let params = match variant.data {
Unit => quote::Ident::from(""),
Tuple(..) => quote::Ident::from("(..)"),
Struct(..) => quote::Ident::from("{..}")
let params = match variant.fields {
Unit => format_ident!(""),
Unnamed(..) => format_ident!("(..)"),
Named(..) => format_ident!("{{..}}")
};

let index = matches.len();
matches.push(quote!{ #name::#ident #params => #index});
}


quote!{
impl #impl_generics enum_index::EnumIndex for #name #ty_generics #where_clause {
fn enum_index(&self) -> usize {
Expand All @@ -53,47 +53,54 @@ fn impl_enum_index(ast: &syn::DeriveInput) -> quote::Tokens {


#[proc_macro_derive(IndexEnum)]
pub fn index_enum(input: TokenStream) -> TokenStream {
let s = input.to_string();
let ast = syn::parse_derive_input(&s).unwrap();
pub fn index_enum(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = parse_macro_input!(input as DeriveInput);

let tokens = impl_index_enum(&ast);
tokens.parse().unwrap()
proc_macro::TokenStream::from(tokens)
}


fn impl_index_enum(ast: &syn::DeriveInput) -> quote::Tokens {
fn impl_index_enum(ast: &syn::DeriveInput) -> proc_macro2::TokenStream {
let name = &ast.ident;
let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();

let variants = match ast.body {
syn::Body::Enum(ref v) => v,
let variants = match ast.data {
syn::Data::Enum(ref v) => &v.variants,
_ => panic!("IndexEnum can be only implemented for Enums")
};

let mut index_matches = Vec::new();
let mut index : usize = 0;

for variant in variants {
use syn::VariantData::*;
use syn::Fields::*;
let ident = &variant.ident;
match variant.data {
match variant.discriminant {
None => {},
Some((_, syn::Expr::Lit(syn::ExprLit { lit: syn::Lit::Int(ref i), .. }))) => {
index = i.base10_parse::<usize>().unwrap();
},
Some(_) => panic!("Unhandled enum discriminant!"),
};

match variant.fields {
Unit => {
index_matches.push(quote! { #index => Some(#name::#ident) });
},
Tuple(ref fields) => {
Unnamed(ref fields) => {
let mut initialized_fields = Vec::new();
for field in fields {
for field in &fields.unnamed {
let field_type = &field.ty;
initialized_fields.push(quote! { #field_type::default()} );
}
index_matches.push(quote! {
#index => Some(#name::#ident(#(#initialized_fields),*))
});
}
Struct(ref fields) => {
Named(ref fields) => {
let mut initialized_fields = Vec::new();
for field in fields {
for field in &fields.named {
let field_name = &field.ident;
let field_type = &field.ty;
initialized_fields.push(quote! { #field_name: #field_type::default()});
Expand All @@ -104,7 +111,6 @@ fn impl_index_enum(ast: &syn::DeriveInput) -> quote::Tokens {
index += 1;
}


quote!{
impl #impl_generics enum_index::IndexEnum for #name #ty_generics #where_clause {
fn index_enum(index: usize) -> Option<Self> {
Expand Down