Don't recover lifetimes/labels containing emojis as character literals

Note that at the time of this commit, `unic-emoji-char` seems to have data tables only up to Unicode 5.0, but Unicode is already newer than this. A newer emoji such as `🥺` will not be recognized as an emoji but older emojis such as `🐱` will.
rust-lang · bors · Feb 18, 2023 · Feb 14, 2023 · Feb 14, 2023 · Feb 14, 2023
commit 380fa264132ad481e73cbbf0f3a0feefd99a1d78
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
@@ -471,6 471,8 @@ pub enum StashKey {
  /// When an invalid lifetime e.g. `'2` should be reinterpreted
  /// as a char literal in the parser
  LifetimeIsChar,
  /// When an invalid lifetime e.g. `'🐱` contains emoji.
  LifetimeContainsEmoji,
  /// Maybe there was a typo where a comma was forgotten before
  /// FRU syntax
  MaybeFruTypo,

diff --git a/compiler/rustc_lexer/src/lib.rs b/compiler/rustc_lexer/src/lib.rs
@@ -95,7 95,7 @@ pub enum TokenKind {
  Literal { kind: LiteralKind, suffix_start: u32 },
 
  /// "'a"
- Lifetime { starts_with_number: bool },
  Lifetime { starts_with_number: bool, contains_emoji: bool },
 
  // One-char tokens:
  /// ";"
@@ -630,7 630,13 @@ impl Cursor<'_> {
  // If the first symbol is valid for identifier, it can be a lifetime.
  // Also check if it's a number for a better error reporting (so '0 will
  // be reported as invalid lifetime and not as unterminated char literal).
- is_id_start(self.first()) || self.first().is_digit(10)
  // We also have to account for potential `'🐱` emojis to avoid reporting
  // it as an unterminated char literal.
  is_id_start(self.first())
  || self.first().is_digit(10)
  // FIXME(#108019): `unic-emoji-char` seems to have data tables only up to Unicode
  // 5.0, but Unicode is already newer than this.
  || unic_emoji_char::is_emoji(self.first())
  };
 
  if !can_be_a_lifetime {
@@ -643,16 649,33 @@ impl Cursor<'_> {
  return Literal { kind, suffix_start };
  }
 
- // Either a lifetime or a character literal with
- // length greater than 1.
  // Either a lifetime or a character literal.
 
  let starts_with_number = self.first().is_digit(10);
  let mut contains_emoji = false;
 
- // Skip the literal contents.
- // First symbol can be a number (which isn't a valid identifier start),
- // so skip it without any checks.
- self.bump();
- self.eat_while(is_id_continue);
  // FIXME(#108019): `unic-emoji-char` seems to have data tables only up to Unicode
  // 5.0, but Unicode is already newer than this.
  if unic_emoji_char::is_emoji(self.first()) {
  contains_emoji = true;
  } else {
  // Skip the literal contents.
  // First symbol can be a number (which isn't a valid identifier start),
  // so skip it without any checks.
  self.bump();
  }
  self.eat_while(|c| {
  if is_id_continue(c) {
  true
  // FIXME(#108019): `unic-emoji-char` seems to have data tables only up to Unicode
  // 5.0, but Unicode is already newer than this.
  } else if unic_emoji_char::is_emoji(c) {
  contains_emoji = true;
  true
  } else {
  false
  }
  });
 
  // Check if after skipping literal contents we've met a closing
  // single quote (which means that user attempted to create a
@@ -662,7 685,7 @@ impl Cursor<'_> {
  let kind = Char { terminated: true };
  Literal { kind, suffix_start: self.pos_within_token() }
  } else {
- Lifetime { starts_with_number }
  Lifetime { starts_with_number, contains_emoji }
  }
  }
 

diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
@@ -200,16 200,21 @@ impl<'a> StringReader<'a> {
  };
  token::Literal(token::Lit { kind, symbol, suffix })
  }
- rustc_lexer::TokenKind::Lifetime { starts_with_number } => {
  rustc_lexer::TokenKind::Lifetime { starts_with_number, contains_emoji } => {
  // 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);
  if starts_with_number {
  let span = self.mk_sp(start, self.pos);
- let mut diag = self.sess.struct_err("lifetimes cannot start with a number");
  let mut diag = self.sess.struct_err("lifetimes or labels cannot start with a number");
  diag.set_span(span);
  diag.stash(span, StashKey::LifetimeIsChar);
  } else if contains_emoji {
  let span = self.mk_sp(start, self.pos);
  let mut diag = self.sess.struct_err("lifetimes or labels cannot contain emojis");
  diag.set_span(span);
  diag.stash(span, StashKey::LifetimeContainsEmoji);
  }
  let ident = Symbol::intern(lifetime_name);
  token::Lifetime(ident)

diff --git a/tests/ui/lexer/issue-108019-bad-emoji-recovery.rs b/tests/ui/lexer/issue-108019-bad-emoji-recovery.rs
@@ -0,0 1,45 @@
 #![allow(unused_labels)]
 
 // FIXME(#108019): outdated Unicode table
 // fn foo() {
 // '🥺 loop {
 // break
 // }
 // }
 
 fn bar() {
  '🐱 loop {
  //~^ ERROR labeled expression must be followed by `:`
  //~| ERROR lifetimes or labels cannot contain emojis
  break
  }
 }
 
 fn qux() {
  'a🐱 loop {
  //~^ ERROR labeled expression must be followed by `:`
  //~| ERROR lifetimes or labels cannot contain emojis
  break
  }
 }
 
 fn quux() {
  '1🐱 loop {
  //~^ ERROR labeled expression must be followed by `:`
  //~| ERROR lifetimes or labels cannot start with a number
  break
  }
 }
 
 fn x<'🐱>() -> &'🐱 () {
  //~^ ERROR lifetimes or labels cannot contain emojis
  //~| ERROR lifetimes or labels cannot contain emojis
  &()
 }
 
 fn y() {
  'a🐱: loop {}
  //~^ ERROR lifetimes or labels cannot contain emojis
 }
 
 fn main() {}
diff --git a/tests/ui/lexer/issue-108019-bad-emoji-recovery.stderr b/tests/ui/lexer/issue-108019-bad-emoji-recovery.stderr
@@ -0,0 1,86 @@
 error: labeled expression must be followed by `:`
  --> $DIR/issue-108019-bad-emoji-recovery.rs:11:5
  |
 LL | '🐱 loop {
  | ^--- help: add `:` after the label
  | |
  | _____the label
  | |
 LL | |
 LL | |
 LL | | break
 LL | | }
  | |_____^
  |
  = note: labels are used before loops and blocks, allowing e.g., `break 'label` to them
 
 error: labeled expression must be followed by `:`
  --> $DIR/issue-108019-bad-emoji-recovery.rs:19:5
  |
 LL | 'a🐱 loop {
  | ^---- help: add `:` after the label
  | |
  | _____the label
  | |
 LL | |
 LL | |
 LL | | break
 LL | | }
  | |_____^
  |
  = note: labels are used before loops and blocks, allowing e.g., `break 'label` to them
 
 error: labeled expression must be followed by `:`
  --> $DIR/issue-108019-bad-emoji-recovery.rs:27:5
  |
 LL | '1🐱 loop {
  | ^---- help: add `:` after the label
  | |
  | _____the label
  | |
 LL | |
 LL | |
 LL | | break
 LL | | }
  | |_____^
  |
  = note: labels are used before loops and blocks, allowing e.g., `break 'label` to them
 
 error: lifetimes or labels cannot contain emojis
  --> $DIR/issue-108019-bad-emoji-recovery.rs:11:5
  |
 LL | '🐱 loop {
  | ^^^
 
 error: lifetimes or labels cannot contain emojis
  --> $DIR/issue-108019-bad-emoji-recovery.rs:19:5
  |
 LL | 'a🐱 loop {
  | ^^^^
 
 error: lifetimes or labels cannot start with a number
  --> $DIR/issue-108019-bad-emoji-recovery.rs:27:5
  |
 LL | '1🐱 loop {
  | ^^^^
 
 error: lifetimes or labels cannot contain emojis
  --> $DIR/issue-108019-bad-emoji-recovery.rs:34:6
  |
 LL | fn x<'🐱>() -> &'🐱 () {
  | ^^^
 
 error: lifetimes or labels cannot contain emojis
  --> $DIR/issue-108019-bad-emoji-recovery.rs:34:16
  |
 LL | fn x<'🐱>() -> &'🐱 () {
  | ^^^
 
 error: lifetimes or labels cannot contain emojis
  --> $DIR/issue-108019-bad-emoji-recovery.rs:41:5
  |
 LL | 'a🐱: loop {}
  | ^^^^
 
 error: aborting due to 9 previous errors