Lex lifetimes as identifiers, recover from emoji and emit appropriate error by estebank · Pull Request #153893 · rust-lang/rust

estebank · 2026-03-15T01:24:54Z

Lex and parse emoji in lifetimes by using the identifier logic, and disallow them in the parser with a hard error. Allow emoji to start a lifetime name even if they are not XID_Start.

error: identifiers cannot contain emoji: `'🐛🐛🐛family👨👩👧👦`
  --> $DIR/emoji-in-lifetime.rs:1:22
   |
LL | fn bad_lifetime_name<'🐛🐛🐛family👨👩👧👦>(
   |                      ^^^^^^^^^^^^^^^^^^^^^

Address #141081 (but we could provide more information in the diagnostic, pointing at the specific chars, providing a link to the reference on identifiers and/or some other extra information).

rustbot · 2026-03-15T01:24:58Z

The parser was modified, potentially altering the grammar of (stable) Rust
which would be a breaking change.

cc @fmease

rustbot · 2026-03-15T01:25:00Z

r? @jdonszelmann

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Kivooeo · 2026-03-15T12:57:59Z

compiler/rustc_lexer/src/lib.rs

        self.bump();
-        self.eat_while(is_id_continue);
+        self.eat_while(|c| {
+            let is_emoji = !c.is_ascii() && c.is_emoji_char();


can we possibly create a function or a method for this, i see this logic is using in two places, maybe something like self.is_emoji() would be better approach?

fmease · 2026-03-15T13:01:58Z

compiler/rustc_parse/src/lexer/mod.rs

+                    if has_emoji {
+                        self.dcx().struct_span_err(span, "lifetimes cannot contain emoji").emit();
+                    }


Why not make use of the preexisting ParseSess.bad_unicode_identifiers & rustc_interface::passes infrastructure?

("lifetime"¹ tokens are a kind of identifier)

Footnotes

Strictly speaking "ticked identifiers" because they don't just represent lifetimes but also labels which have a distinct grammar (e.g., 'static is not a syntactically valid label but it is a lexically valid ~~"lifetime"~~ ticked identifier) ↩

The main reason to not do that is to still leverage the 'blah' recovery machinery. Here we are in a situation where we have to either choose one case to have nicer output than the other, or find a good way to unify both checks.

Lex and parse emoji in lifetimes, and disallow them in the parser with a hard error. Allow emoji to start a lifetime name even if they are not XID_Start. ``` error: lifetimes cannot contain emoji --> $DIR/emoji-in-lifetime.rs:1:22 | LL | fn bad_lifetime_name<'🐛🐛🐛family👨👩👧👦>( | ^^^^^^^^^^^^^^^^^^^^^ ```

rustbot · 2026-03-18T18:10:01Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

rustbot · 2026-03-18T18:38:25Z

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

Veykril

rust-analyzer side

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jdonszelmann · 2026-03-30T15:11:03Z

I agree with esteban for the nicer suggestions here, that's probably worth it. Sorry it took me a while, but lgtm.

@bors r=me,veykril rollup

rust-bors · 2026-03-30T15:11:09Z

📌 Commit 4f1676d has been approved by me,veykril

It is now in the queue for this repository.

⚠️ The following reviewer(s) could not be found: me

fmease · 2026-03-30T15:25:13Z

@bors r=jdonszelmann,Veykril

rust-bors · 2026-03-30T15:25:16Z

📌 Commit 4f1676d has been approved by jdonszelmann,Veykril

It is now in the queue for this repository.

…lmann,Veykril Lex lifetimes as identifiers, recover from emoji and emit appropriate error Lex and parse emoji in lifetimes by using the identifier logic, and disallow them in the parser with a hard error. Allow emoji to start a lifetime name even if they are not XID_Start. ``` error: identifiers cannot contain emoji: `'🐛🐛🐛family👨👩👧👦` --> $DIR/emoji-in-lifetime.rs:1:22 | LL | fn bad_lifetime_name<'🐛🐛🐛family👨👩👧👦>( | ^^^^^^^^^^^^^^^^^^^^^ ``` Address rust-lang#141081 (but we could provide more information in the diagnostic, pointing at the specific chars, providing a link to the reference on identifiers and/or some other extra information).

Rollup of 7 pull requests Successful merges: - #142659 (compiler-builtins: Clean up features) - #153574 (Avoid ICE when param-env normalization leaves unresolved inference variables) - #153648 (Fix EII function aliases eliminated by LTO) - #153790 (Fix regression when dealing with generics/values with unresolved inference) - #153893 (Lex lifetimes as identifiers, recover from emoji and emit appropriate error) - #153980 (refactor: move doc(rust_logo) check to parser) - #154551 (Skip suggestions pointing to macro def for assert_eq)

Zalathar · 2026-03-31T05:32:00Z

Failed in rollup: #154611 (comment)

@bors r-
@bors try jobs=dist-ohos-armv7

rust-bors · 2026-03-31T05:32:08Z

This pull request was unapproved.

This PR was contained in a rollup (#154611), which was unapproved.

Lex lifetimes as identifiers, recover from emoji and emit appropriate error try-job: dist-ohos-armv7

rust-bors · 2026-03-31T06:28:20Z

💔 Test for 8db3bb9 failed: CI. Failed job:

try - dist-ohos-armv7 (web logs, enhanced plaintext logs)

rust-log-analyzer · 2026-03-31T06:28:24Z

The job dist-ohos-armv7 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

258 |                 rustc_lexer::TokenKind::Lifetime { invalid, starts_with_number } => {
    |                                                           ++++++++++++++++++++
help: if you don't care about this missing field, you can explicitly ignore it
    |
258 |                 rustc_lexer::TokenKind::Lifetime { invalid, starts_with_number: _ } => {
    |                                                           +++++++++++++++++++++++
help: or always ignore missing fields here
    |
258 |                 rustc_lexer::TokenKind::Lifetime { invalid, .. } => {
    |                                                           ++++

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 15, 2026

rustbot assigned jdonszelmann Mar 15, 2026

estebank mentioned this pull request Mar 15, 2026

Confusing error when using non-XID_Start characters in lifetime names #141081

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estebank force-pushed the emoji-lifetime branch from 8679628 to cf3c735 Compare March 15, 2026 03:59

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Kivooeo reviewed Mar 15, 2026

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fmease reviewed Mar 15, 2026

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estebank force-pushed the emoji-lifetime branch from cf3c735 to a45ca0d Compare March 18, 2026 18:09

Unify lifetime and identifier parsing

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estebank force-pushed the emoji-lifetime branch from a45ca0d to dfdc525 Compare March 18, 2026 18:11

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estebank added 2 commits March 18, 2026 18:32

Use bad_unicode_identifiers for lifetimes

702197a

Fix rust-analyzer

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rustbot added the T-rust-analyzer Relevant to the rust-analyzer team, which will review and decide on the PR/issue. label Mar 18, 2026

remove whitespace

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fix test

4f1676d

estebank changed the title ~~Lex lifetimes using emoji and emit appropriate error~~ Lex lifetimes as identifiers, recover from emoji and emit appropriate error Mar 19, 2026

Veykril approved these changes Mar 19, 2026

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rust-bors bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 30, 2026

tgross35 mentioned this pull request Mar 30, 2026

Rollup of 7 pull requests #154611

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rust-bors bot pushed a commit that referenced this pull request Mar 31, 2026

Auto merge of #153893 - estebank:emoji-lifetime, r=<try>

8db3bb9

Lex lifetimes as identifiers, recover from emoji and emit appropriate error try-job: dist-ohos-armv7

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