1use proc_macro::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
2use std::fmt::Display;
3use std::iter::FromIterator;
4
5pub type Result<T, E = Error> = std::result::Result<T, E>;
6
7pub struct Error {
8 begin: Span,
9 end: Span,
10 msg: String,
11}
12
13impl Error {
14 pub fn new(span: Span, msg: impl Display) -> Self {
15 Self::new2(span, span, msg)
16 }
17
18 pub fn new2(begin: Span, end: Span, msg: impl Display) -> Self {
19 Error {
20 begin,
21 end,
22 msg: msg.to_string(),
23 }
24 }
25
26 pub fn group(group: Group, msg: impl Display) -> Self {
27 let mut iter = group.stream().into_iter();
28 let delimiter = group.span();
29 let begin = iter.next().map_or(delimiter, |t| t.span());
30 let end = iter.last().map_or(begin, |t| t.span());
31 Self::new2(begin, end, msg)
32 }
33
34 pub fn into_compile_error(self) -> TokenStream {
35 // compile_error! { $msg }
36 TokenStream::from_iter(vec![
37 TokenTree::Ident(Ident::new("compile_error", self.begin)),
38 TokenTree::Punct({
39 let mut punct = Punct::new('!', Spacing::Alone);
40 punct.set_span(self.begin);
41 punct
42 }),
43 TokenTree::Group({
44 let mut group = Group::new(Delimiter::Brace, {
45 TokenStream::from_iter(vec![TokenTree::Literal({
46 let mut string = Literal::string(&self.msg);
47 string.set_span(self.end);
48 string
49 })])
50 });
51 group.set_span(self.end);
52 group
53 }),
54 ])
55 }
56}
57