Rollup merge of #64226 - alexreg:rush-pr-3, r=centril

Aggregation of cosmetic changes made during work on REPL PRs: libsyntax

Factored out from hacking on rustc for work on the REPL.

r? @Centril

diff --cc src/libsyntax/feature_gate/active.rs
Simple merge

diff --cc src/libsyntax/parse/mod.rs
index 981f5f1f7b004ca6d209235962977d09c16e9fcd,aa57c3954e352f66656efb73375440b6eede0b1a..bc1bc00ac84054ac0f359bec86e52aafd66ba259
--- 1/src/libsyntax/parse/mod.rs
--- 2/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@@ -90,8 -95,10 +92,9 @@@ impl ParseSess 
              span_diagnostic: handler,
              unstable_features: UnstableFeatures::from_environment(),
              config: FxHashSet::default(),
+             edition: ExpnId::root().expn_data().edition,
              missing_fragment_specifiers: Lock::new(FxHashSet::default()),
              raw_identifier_spans: Lock::new(Vec::new()),
 -            registered_diagnostics: Lock::new(ErrorMap::new()),
              included_mod_stack: Lock::new(vec![]),
              source_map,
              buffered_lints: Lock::new(vec![]),