74 lines
2.2 KiB
Rust
74 lines
2.2 KiB
Rust
// nifty utility borrowed from serde :)
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// https://github.com/serde-rs/serde/blob/master/serde_derive/src/internals/ctxt.rs
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use std::cell::RefCell;
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use std::fmt::Display;
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use std::thread;
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use proc_macro2::TokenStream;
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use quote::{quote, ToTokens};
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use syn;
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/// A type to collect errors together and format them.
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///
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/// Dropping this object will cause a panic. It must be consumed using `check`.
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///
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/// References can be shared since this type uses run-time exclusive mut checking.
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#[derive(Default)]
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pub struct Ctxt {
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// The contents will be set to `None` during checking. This is so that checking can be
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// enforced.
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errors: RefCell<Option<Vec<syn::Error>>>,
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}
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impl Ctxt {
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/// Create a new context object.
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///
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/// This object contains no errors, but will still trigger a panic if it is not `check`ed.
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pub fn new() -> Self {
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Ctxt {
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errors: RefCell::new(Some(Vec::new())),
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}
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}
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/// Add an error to the context object with a tokenenizable object.
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///
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/// The object is used for spanning in error messages.
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pub fn error_spanned_by<A: ToTokens, T: Display>(&self, obj: A, msg: T) {
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self.errors
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.borrow_mut()
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.as_mut()
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.unwrap()
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// Curb monomorphization from generating too many identical methods.
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.push(syn::Error::new_spanned(obj.into_token_stream(), msg));
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}
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/// Add one of Syn's parse errors.
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#[allow(unused)]
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pub fn syn_error(&self, err: syn::Error) {
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self.errors.borrow_mut().as_mut().unwrap().push(err);
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}
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/// Consume this object, producing a formatted error string if there are errors.
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pub fn check(self) -> Result<(), TokenStream> {
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let errors = self.errors.borrow_mut().take().unwrap();
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match errors.len() {
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0 => Ok(()),
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_ => Err(to_compile_errors(errors)),
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}
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}
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}
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fn to_compile_errors(errors: Vec<syn::Error>) -> proc_macro2::TokenStream {
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let compile_errors = errors.iter().map(syn::Error::to_compile_error);
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quote!(#(#compile_errors)*)
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}
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impl Drop for Ctxt {
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fn drop(&mut self) {
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if !thread::panicking() && self.errors.borrow().is_some() {
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panic!("forgot to check for errors");
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}
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}
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}
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