#![deny(unused_must_use)]
-use quote::format_ident;
-use quote::quote;
-
use proc_macro::Diagnostic;
+use quote::{format_ident, quote};
use syn::spanned::Spanned;
-use std::collections::{HashMap, HashSet};
+use std::collections::{BTreeSet, HashMap};
/// Implements #[derive(SessionDiagnostic)], which allows for errors to be specified as a struct, independent
/// from the actual diagnostics emitting code.
/// ```
/// This function builds the entire call to format!.
fn build_format(&self, input: &String, span: proc_macro2::Span) -> proc_macro2::TokenStream {
- let mut referenced_fields: HashSet<String> = HashSet::new();
+ // This set is used later to generate the final format string. To keep builds reproducible,
+ // the iteration order needs to be deterministic, hence why we use a BTreeSet here instead
+ // of a HashSet.
+ let mut referenced_fields: BTreeSet<String> = BTreeSet::new();
// At this point, we can start parsing the format string.
let mut it = input.chars().peekable();