use proc_macro::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree}; use std::fmt::Display; use std::iter::FromIterator; pub type Result = std::result::Result; 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 }), ]) } }