easy_ext/
error.rs

1// SPDX-License-Identifier: Apache-2.0 OR MIT
2
3use std::iter::FromIterator;
4
5use proc_macro::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
6
7use crate::to_tokens::ToTokens;
8
9macro_rules! format_err {
10    ($span:expr, $msg:expr $(,)*) => {
11        crate::error::Error::new(&$span, String::from($msg))
12    };
13    ($span:expr, $($tt:tt)*) => {
14        format_err!($span, format!($($tt)*))
15    };
16}
17
18macro_rules! bail {
19    ($($tt:tt)*) => {
20        return Err(format_err!($($tt)*))
21    };
22}
23
24pub(crate) type Result<T, E = Error> = std::result::Result<T, E>;
25
26#[derive(Debug)]
27pub(crate) struct Error {
28    start_span: Span,
29    end_span: Span,
30    msg: String,
31}
32
33impl Error {
34    pub(crate) fn new(tokens: &dyn ToTokens, msg: String) -> Self {
35        let mut iter = tokens.to_token_stream().into_iter();
36        // `Span` on stable Rust has a limitation that only points to the first
37        // token, not the whole tokens. We can work around this limitation by
38        // using the first/last span of the tokens like `syn::Error::new_spanned` does.
39        let start_span = iter.next().map_or_else(Span::call_site, |t| t.span());
40        let end_span = iter.last().map_or(start_span, |t| t.span());
41
42        Self { start_span, end_span, msg }
43    }
44
45    // Based on https://github.com/dtolnay/syn/blob/1.0.39/src/error.rs#L210-L237
46    pub(crate) fn into_compile_error(self) -> TokenStream {
47        // compile_error!($msg)
48        TokenStream::from_iter(vec![
49            TokenTree::Ident(Ident::new("compile_error", self.start_span)),
50            TokenTree::Punct({
51                let mut punct = Punct::new('!', Spacing::Alone);
52                punct.set_span(self.start_span);
53                punct
54            }),
55            TokenTree::Group({
56                let mut group = Group::new(Delimiter::Brace, {
57                    TokenStream::from_iter(vec![TokenTree::Literal({
58                        let mut string = Literal::string(&self.msg);
59                        string.set_span(self.end_span);
60                        string
61                    })])
62                });
63                group.set_span(self.end_span);
64                group
65            }),
66        ])
67    }
68}
easy_ext/error.rs

easy_ext/
error.rs
