1use quote::ToTokens;
2use std::cell::RefCell;
3use std::fmt::Display;
4use std::thread;
5
6/// A type to collect errors together and format them.
7///
8/// Dropping this object will cause a panic. It must be consumed using `check`.
9///
10/// References can be shared since this type uses run-time exclusive mut checking.
11#[derive(Default)]
12pub struct Ctxt {
13 // The contents will be set to `None` during checking. This is so that checking can be
14 // enforced.
15 errors: RefCell<Option<Vec<syn::Error>>>,
16}
17
18impl Ctxt {
19 /// Create a new context object.
20 ///
21 /// This object contains no errors, but will still trigger a panic if it is not `check`ed.
22 pub fn new() -> Self {
23 Ctxt {
24 errors: RefCell::new(Some(Vec::new())),
25 }
26 }
27
28 /// Add an error to the context object with a tokenenizable object.
29 ///
30 /// The object is used for spanning in error messages.
31 pub fn error_spanned_by<A: ToTokens, T: Display>(&self, obj: A, msg: T) {
32 self.errors
33 .borrow_mut()
34 .as_mut()
35 .unwrap()
36 // Curb monomorphization from generating too many identical methods.
37 .push(syn::Error::new_spanned(obj.into_token_stream(), msg));
38 }
39
40 /// Add one of Syn's parse errors.
41 pub fn syn_error(&self, err: syn::Error) {
42 self.errors.borrow_mut().as_mut().unwrap().push(err);
43 }
44
45 /// Consume this object, producing a formatted error string if there are errors.
46 pub fn check(self) -> syn::Result<()> {
47 let mut errors = self.errors.borrow_mut().take().unwrap().into_iter();
48
49 let mut combined = match errors.next() {
50 Some(first) => first,
51 None => return Ok(()),
52 };
53
54 for rest in errors {
55 combined.combine(rest);
56 }
57
58 Err(combined)
59 }
60}
61
62impl Drop for Ctxt {
63 fn drop(&mut self) {
64 if !thread::panicking() && self.errors.borrow().is_some() {
65 panic!("forgot to check for errors");
66 }
67 }
68}
69