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use proc_macro2::Span;
use syn::parse::{Error, Parse, ParseStream, Result};
use syn::{Attribute, ItemImpl, ItemTrait, Token};
pub enum Item {
Trait(ItemTrait),
Impl(ItemImpl),
}
impl Parse for Item {
fn parse(input: ParseStream) -> Result<Self> {
let attrs = input.call(Attribute::parse_outer)?;
let mut lookahead = input.lookahead1();
if lookahead.peek(Token![unsafe]) {
let ahead = input.fork();
ahead.parse::<Token![unsafe]>()?;
lookahead = ahead.lookahead1();
}
if lookahead.peek(Token![pub]) || lookahead.peek(Token![trait]) {
let mut item: ItemTrait = input.parse()?;
item.attrs = attrs;
Ok(Item::Trait(item))
} else if lookahead.peek(Token![impl]) {
let mut item: ItemImpl = input.parse()?;
if item.trait_.is_none() {
return Err(Error::new(Span::call_site(), "expected a trait impl"));
}
item.attrs = attrs;
Ok(Item::Impl(item))
} else {
Err(lookahead.error())
}
}
}
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