NFC normalize lifetime identifiers

compiler/rustc_parse/src/lexer/mod.rs

@@ -316,7 +316,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
                     // Include the leading `'` in the real identifier, for macro
                     // expansion purposes. See #12512 for the gory details of why
                     // this is necessary.
-                    let lifetime_name = self.str_from(start);
+                    let lifetime_name = nfc_normalize(self.str_from(start));
                     self.last_lifetime = Some(self.mk_sp(start, start + BytePos(1)));
                     if starts_with_number {
                         let span = self.mk_sp(start, self.pos);
@@ -325,8 +325,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
                             .with_span(span)
                             .stash(span, StashKey::LifetimeIsChar);
                     }
-                    let ident = Symbol::intern(lifetime_name);
-                    token::Lifetime(ident, IdentIsRaw::No)
+                    token::Lifetime(lifetime_name, IdentIsRaw::No)
                 }
                 rustc_lexer::TokenKind::RawLifetime => {
                     self.last_lifetime = Some(self.mk_sp(start, start + BytePos(1)));
@@ -373,7 +372,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
                             String::with_capacity(lifetime_name_without_tick.as_str().len() + 1);
                         lifetime_name.push('\'');
                         lifetime_name += lifetime_name_without_tick.as_str();
-                        let sym = Symbol::intern(&lifetime_name);
+                        let sym = nfc_normalize(&lifetime_name);
 
                         // Make sure we mark this as a raw identifier.
                         self.psess.raw_identifier_spans.push(span);
@@ -393,9 +392,8 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
                         self.pos = lt_start;
                         self.cursor = Cursor::new(&str_before[2 as usize..], FrontmatterAllowed::No);
 
-                        let lifetime_name = self.str_from(start);
-                        let ident = Symbol::intern(lifetime_name);
-                        token::Lifetime(ident, IdentIsRaw::No)
+                        let lifetime_name = nfc_normalize(self.str_from(start));
+                        token::Lifetime(lifetime_name, IdentIsRaw::No)
                     }
                 }
                 rustc_lexer::TokenKind::Semi => token::Semi,

tests/ui/lexer/ident_normalization.rs

@@ -0,0 +1,20 @@
+//@check-pass
+//@edition:2021
+
+#![allow(non_snake_case)]
+
+// Tests that identifiers are NFC-normalized as per
+// https://rust-lang.github.io/rfcs/2457-non-ascii-idents.html
+
+// Note that in the first argument of each function `K` is LATIN CAPITAL LETTER K
+// and in the second it is K (KELVIN SIGN).
+
+fn ident_nfc<K>(_p1: K, _p2: K) {}
+
+fn raw_ident_nfc<K>(_p1: r#K, _p2: r#K) {}
+
+fn lifetime_nfc<'K>(_p1: &'K str, _p2: &'K str) {}
+
+fn raw_lifetime_nfc<'K>(_p1: &'r#K str, _p2: &'r#K str) {}
+
+fn main() {}