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use proc_macro::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
use std::fmt::Display;
use std::iter::FromIterator;
pub type Result<T, E = Error> = std::result::Result<T, E>;
pub struct Error {
begin: Span,
end: Span,
msg: String,
}
impl Error {
pub fn new(span: Span, msg: impl Display) -> Self {
Self::new2(span, span, msg)
}
pub fn new2(begin: Span, end: Span, msg: impl Display) -> Self {
Error {
begin,
end,
msg: msg.to_string(),
}
}
pub fn group(group: Group, msg: impl Display) -> Self {
let mut iter = group.stream().into_iter();
let delimiter = group.span();
let begin = iter.next().map_or(delimiter, |t| t.span());
let end = iter.last().map_or(begin, |t| t.span());
Self::new2(begin, end, msg)
}
pub fn into_compile_error(self) -> TokenStream {
// compile_error! { $msg }
TokenStream::from_iter(vec![
TokenTree::Ident(Ident::new("compile_error", self.begin)),
TokenTree::Punct({
let mut punct = Punct::new('!', Spacing::Alone);
punct.set_span(self.begin);
punct
}),
TokenTree::Group({
let mut group = Group::new(Delimiter::Brace, {
TokenStream::from_iter(vec![TokenTree::Literal({
let mut string = Literal::string(&self.msg);
string.set_span(self.end);
string
})])
});
group.set_span(self.end);
group
}),
])
}
}
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