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use quote::ToTokens;
use std::cell::RefCell;
use std::fmt::Display;
use std::thread;
/// A type to collect errors together and format them.
///
/// Dropping this object will cause a panic. It must be consumed using `check`.
///
/// References can be shared since this type uses run-time exclusive mut checking.
#[derive(Default)]
pub struct Ctxt {
// The contents will be set to `None` during checking. This is so that checking can be
// enforced.
errors: RefCell<Option<Vec<syn::Error>>>,
}
impl Ctxt {
/// Create a new context object.
///
/// This object contains no errors, but will still trigger a panic if it is not `check`ed.
pub fn new() -> Self {
Ctxt {
errors: RefCell::new(Some(Vec::new())),
}
}
/// Add an error to the context object with a tokenenizable object.
///
/// The object is used for spanning in error messages.
pub fn error_spanned_by<A: ToTokens, T: Display>(&self, obj: A, msg: T) {
self.errors
.borrow_mut()
.as_mut()
.unwrap()
// Curb monomorphization from generating too many identical methods.
.push(syn::Error::new_spanned(obj.into_token_stream(), msg));
}
/// Add one of Syn's parse errors.
pub fn syn_error(&self, err: syn::Error) {
self.errors.borrow_mut().as_mut().unwrap().push(err);
}
/// Consume this object, producing a formatted error string if there are errors.
pub fn check(self) -> syn::Result<()> {
let mut errors = self.errors.borrow_mut().take().unwrap().into_iter();
let mut combined = match errors.next() {
Some(first) => first,
None => return Ok(()),
};
for rest in errors {
combined.combine(rest);
}
Err(combined)
}
}
impl Drop for Ctxt {
fn drop(&mut self) {
if !thread::panicking() && self.errors.borrow().is_some() {
panic!("forgot to check for errors");
}
}
}