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Rollup merge of #76515 - jumbatm:issue76496-reproducibility-regression, r=oli-obk

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SessionDiagnostic: Fix non-determinism in generated format string.

Fixes #76496.

r? @oli-obk
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Tyler Mandry 2020-09-09 15:06:02 -07:00 committed by GitHub
commit 98f59bc2aa
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1 changed files with 6 additions and 5 deletions
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11
compiler/rustc_macros/src/session_diagnostic.rs
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@ -1,11 +1,9 @@
#![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.
@ -577,7 +575,10 @@ impl<'a> SessionDiagnosticDeriveBuilder<'a> {
/// ```
/// 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();