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#![crate_type = "proc-macro"]
extern crate proc_macro;
use proc_macro::TokenStream;
use quote::{quote, quote_each_token, Tokens};
use syn::{Lit, MetaItem, NestedMetaItem};
#[doc(hidden)]
#[proc_macro_derive(NamedType, attributes(named_type))]
pub fn derive(input: TokenStream) -> TokenStream {
let input = input.to_string();
let ast = syn::parse_macro_input(&input).expect("Couldn't parse item");
let result = named_type_derive(ast).to_string();
result
.parse()
.expect(&format!("Couldn't parse `{}` to tokens", result))
}
fn find_prefix_suffix(props: &Vec<NestedMetaItem>) -> Option<(&str, &str)> {
let prefix = props
.iter()
.find(|item| match item {
&&NestedMetaItem::MetaItem(MetaItem::NameValue(ref ident, _)) => {
ident == "short_prefix"
}
_ => false,
})
.and_then(|item| match item {
&NestedMetaItem::MetaItem(MetaItem::NameValue(_, ref value)) => match value {
&Lit::Str(ref string, _) => Some(string.as_ref()),
_ => None,
},
_ => None,
})
.unwrap_or("");
let suffix = props
.iter()
.find(|item| match item {
&&NestedMetaItem::MetaItem(MetaItem::NameValue(ref ident, _)) => {
ident.to_string() == "short_suffix"
}
_ => false,
})
.and_then(|item| match item {
&NestedMetaItem::MetaItem(MetaItem::NameValue(_, ref value)) => match value {
&Lit::Str(ref string, _) => Some(string.as_ref()),
_ => None,
},
_ => None,
})
.unwrap_or("");
Some((prefix, suffix))
}
fn named_type_derive(ast: syn::MacroInput) -> Tokens {
let name = &ast.ident;
let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
let (prefix, suffix) = {
ast.attrs
.iter()
.find(|attr| match &attr.value {
&MetaItem::List(ref ident, _) => ident == "named_type",
_ => false,
})
.and_then(|attr| match &attr.value {
&MetaItem::List(_, ref props) => find_prefix_suffix(props),
_ => None,
})
.unwrap_or(("", ""))
};
let short_type_name: String = format!("{}{}{}", prefix, name, suffix);
quote! {
impl #impl_generics NamedType for #name #ty_generics #where_clause {
fn type_name() -> &'static str {
concat!(module_path!(), "::", stringify!(#name))
}
fn short_type_name() -> &'static str {
#short_type_name
}
}
}
}